Symposium Organizers
Ingrid Graz, Johannes Kepler University Linz
Anastasia Elias, University of Alberta
Ivan Minev, Technische Universität Dresden
Benjamin O'Brien, StretchSense
BM09.01: Applications I
Session Chairs
Anastasia Elias
Ingrid Graz
Ivan Minev
Monday PM, November 27, 2017
Sheraton, 2nd Floor, Republic B
8:30 AM - *BM09.01.01
Wearable/Disposable Sweat-Based Glucose Sensor
Dae-Hyeong Kim 2 1
2 Center for Nanoparticle Research, Institute for Basic Science, Seoul Korea (the Republic of), 1 , Seoul National University, Seoul Korea (the Republic of)
Show AbstractRecent advances in soft electronics have attracted great attention due in large to the potential applications in personalized bio-integrated healthcare devices. The mechanical mismatch between conventional electronic devices and soft human tissues causes many challenges. Ultraflexible and stretchable electronic devices utilize the low system modulus and the intrinsic system-level softness to solve these issues. Here, we describe our unique strategies in synthesis and functionalization of nanoscale materials, their seamless assembly and integration with flexible device platforms to develope wearable/disposable glucose sesning devices. Additional combination of skin-mounted microneedles allows feedback control of glucose levels via transdermal drug delivery. These wearable/disposable bioelectronic systems combine recent breakthroughs in unconventional soft electronics to address unsolved issues in the clinical medicine, particularly in diabetes mellitus.
9:00 AM - BM09.01.02
Wearable Sensors and Actuators for Translating Gestures and Stimulating the Tactile Sense
Darren Lipomi 1
1 , University of California, San Diego, La Jolla, California, United States
Show AbstractWe are developing a new type of platform for combined sensor-actuator skin platform using carbon nanomaterials and semiconducting polymers for human-machine interfaces for virtual and augmented reality. In particular, we have developed a glove that can translate the letters of American Sign Language to text visible on a mobile phone. This glove can be used to actuate a hand in virtual reality, and also a robotic hand in the laboratory. The robotic hand can be fitted with sensors designed to measure the pressure and temperature at the fingertips, and force sensors designed to measure the physical resistance of solid objects. These data are then transmitted back to the glove of the wearer, where they are translated into pressure signals triggered by soft electrotactile actuators in the fingertips and temperature signals using flexible organic thermoelectric devices on the interior surface of the glove. The sensation of physical resistance of an object—the kinesthetic actuation—is provided by a glassy polymer whose glass transition temperature is approximately equal to that of the surface of the skin. Thermoelectric cooling causes this material to become rigid and mimics the sensation of grasping solid objects. This project represents the intersection between soft materials science and the sense of touch, or what we call “organic haptics.”
9:15 AM - BM09.01.03
Pectin-Based E-Skin for Large Area and High Sensitivity Temperature Mapping
Vincenzo Costanza 1 , Luca Bonanomi 1 2 , Chiara Daraio 1
1 , California Institute of Technology, Pasadena, California, United States, 2 Mechanical and Process Engineering, ETH Zürich, Zürich Switzerland
Show AbstractElectronic skins (e-skin) are flexible sensor networks that can spatially map different external stimuli. E-skins can have countless potential applications in robotics, high-tech prosthetics as well as wearable healthcare. In order to be effective, skin-like networks have to detect a wide range of sensations including temperature, pressure, strain and vibrations, with high spatial resolutions, response and sensitivity. Although pressure, force and strain sensors have been successfully integrated in e-skin platforms, temperature mapping still remains a challenge. Current approaches present limited temperature response, sensitivity or operating range. Recently, we reported pectin-based films, which exploit temperature-mediated ionic conductivity to achieve a giant temperature response, high sensitivity and wide operating range. Pectin films show a temperature responsivity at least two order of magnitudes higher than current technologies, sensitivity of 10mK and operate over a temperature range of circa 60 C°. Here, we demonstrate a large area temperature mapping e-skin based on pectin films. We present a fully integrated temperature sensitive film, embedded in a 3D printed layered structure, which encloses the electrodes and the insulating layers. These films can be bent and conformably applied on different surfaces to map temperature. We show the complete AC response of the pectin films between 1 Hz and 5 MHz. We demonstrate that the phase shift is also greatly affected by temperature variations. We show that phase detection can be an alternative to amplitude measurement to accurately measure temperature. Phase detection also allows to extend the excitation frequency range, enabling multiplexing techniques with a large number of pixels for high spatial resolution mapping.
9:30 AM - BM09.01.04
Skin Attachable Temperature Sensor with Octopus Mimicking Micro-Structured Adhesive
Ju hyun Oh 1 , Soo Yeong Hong 1 , Heun Park 1 , Sang Woo Jin 2 , Yura Jeong 1 , Seung Yun Oh 2 , Jeong Sook Ha 1 2
1 Chemical and Biological Engineering, Korea University, Seoul Korea (the Republic of), 2 , KU-KIST Graduate School of Converging Science and Technology, Seoul Korea (the Republic of)
Show AbstractAlong with the increased desire for monitoring personal health conditions, there have been extensive efforts to develop high performance skin-attachable sensor devices which can detect bio-signals such as skin temperature, blood pressure and heart-rate. Thus, having adhesive conformally attachable to skin has become as important as getting highly sensitive sensors.
In this study, we demonstrate a highly sensitive flexible temperature sensor with bio-inspired octopus adhesive. A resistor type sensor is fabricated with a composite of poly(N-isopropylacrylamide)(pNIPAM)/ pNIPAM/poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS)/carbon nanotube (CNT), which was prepared by soaking PEDOT:PSS/CNT into thermally responsive hydrogel, pNIPAM layer. As the temperature increases, pNIPAM de-swells to have dense percolation network for PEDOT:PSS/CNT. With this sensor, very high sensitivity of 2.6 %/°C is obtained in the temperature range between 25° and 40°C, and a very small change in temperature of 0.5°C can be detected.
The adhesive layer is fabricated using octopus mimicking rim structure of PDMS coated with pNIPAM, which is responsive to the skin temperature of 33 to 35 °C. Thus, the adhesion increases when it contacts with skin via suction mechanism due to sealing effect from rim structure and de-swelling from pNIPAM. At the same time, skin temperature can be also measured. The fabricated pNIPAM coated PDMS layer exhibits adhesion of 3.7 kPa, 23 times higher than that of ordinary PDMS at room temperature while it increases 6 times to have 13.4 kPa at 40°C. This work demonstrates a facile fabrication of a highly sensitive skin-attachable temperature sensor with non-irritating adhesion via octopus mimicking micro-structures and use of thermally responsive pNIPAM, suggesting a high potential application to wearable sensors for medical and healthcare monitoring.
9:45 AM - BM09.01.05
Magnetic E-Skins Enabled Somatic and Touchless Interactive Devices
Jin Ge 1 , Xu Wang 1 , Gilbert Santiago Canon Bermudez 1 , ChangAn Wang 1 , Shengqiang Zhou 1 , Juergen Fassbender 1 , Denys Makarov 1
1 , Helmholtz-Zentrum Dresden-Rossendorf e.V., Institute of Ion Beam Physics and Materials Research, Dresden Germany
Show AbstractHumans skin provide perceptions of the temperature of objects, strain and pressure on skin and friction for holding objects, which help humans interact very precisely with unstructured surroundings [1]. Electronic skins [2-4] allow for the realization of similar sensing functions and also have the possibility of integrating other sensing functions beyond humans, for example, touchless feeling. Very recently we demonstrated magnetosensitive e-skins, which is an important step towards the realization of artificial magnetoception for humans [5,6].
Here, we present a magnetic e-skin that not only has the ability to detect the position and movement of magnetic objects in a touchless manner but also is sensitive to mechanical forces. The magnetic skin is a stack of a magnetoresistive (MR) sensor layer and a surface-pyramid-structured magnetic foil. The MR sensor of the magnetic e-skin enables the sensing of the surrounding magnetic field change. When an object’s surface is fixed with a magnet, the magnetic e-skin will be able to detect the distance change between itself and the object (touchless interaction). Furthermore, when a pressure is applied on the magnetic e-skin, the distance change between the MR sensor and the magnetic foil will change, which will also result in the resistance change of the MR sensor. As a result, this magnetic e-skin also has the ability of detecting the pressure change applied on its surface (somatic interaction). This multi-functional magnetic e-skin will hold great promise for the realization of advanced humanoid robots, biomedical prostheses, and surgical electronic gloves.
[1] A. Zimmerman, et al. Science 346, 950 (2014).
[2] T. Someya, et al. Proc. Natl. Acad. Sci. U.S.A. 101, 9966 (2004).
[3] Z. Ma, et al. Science 333, 830 (2011).
[4] Z. Bao, et al. Adv. Mater. 25, 5997 (2013).
[5] M. Melzer, et al, Nat. Commun. 6, 6080 (2015).
[6] D. Makarov, et al., Appl. Phys. Rev. 3, 011101 (2016).
10:30 AM - *BM09.01.06
Low-Cost Manufacture and Multi-Faceted Applications of Electronic Tattoos
Nanshu Lu 1
1 , The University of Texas at Austin, Austin, Texas, United States
Show AbstractBio-tissues are soft, curvilinear and dynamic whereas wafer-based electronics are hard, planar and fragile, which fundamentally impedes their integration with each other. Stretchable electronics offer a long-desired solution to such mechanical mismatch. Among the diverse family of stretchable electronics, Electronic tattoos (E-Tattoos) represent a class of stretchable circuits and sensors that are ultrathin, ultrasoft, skin-conformable and deformable, just like a secondary skin. Ideally, E-Tattoos should be disposable, hence their low-cost, high-yield manufacture is critical to its success. This talk introduces a low-cost and freeform “cut-and-paste” method to fabricate E-Tattoos within minutes. This method has been proved to work for thin film metals, thin film ceramics, polymer sheets, as well as 2D materials such as graphene. E-Tattoos manufactured by the cut-and-paste method can be as thin as 500 nm, stretchable beyond 100%, up to 85% transparency, wireless, and multi-functional. I will discuss applying such disposable E-Tattoos for the measurements of electroencephalogram (EEG), electrooculogram (EOG), electrocardiogram (ECG), seismocardiogram (SCG), electromyogram (EMG), skin temperature, skin hydration, respiratory rate, and oxygen saturation. Estimation of beat-to-beat blood pressure using such an E-Tattoo is also possible. Several Bluetooth and NFC-enabled wireless E-Tattoos will be introduced. Applications of such E-Tattoos as mobile health (mHealth) monitors and human-machine interfaces (HMI) will also be demonstrated.
11:00 AM - BM09.01.07
Fully Printed E-Skin Multi-Sensor
Eloise Bihar 1 , Yi Zhang 1 , Derya Baran 1 , Sahika Inal 1
1 , King Abdullah University of Science and Technology (KAUST), Thuwal Saudi Arabia
Show AbstractThe ever-growing demands in healthcare industry require the development of low-cost and easy-to-use tools and strategies for the early diagnosis and prevention of disease such as diabetes or cardiovascular disease. Monitoring human metabolite levels (such as glucose, lactate, cholesterol etc) can provide useful information regarding key metabolic activities in the human body and detect associated irregularities.
In this work we show a portable and user-friendly metabolite sensing device for continuous and multiparameter monitoring of key physiological activities. We use the biocompatible conducting polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and additive printing technologies such as inkjet printing toward the realization of high performance biosensing devices. The developed platform consists of multiple, printed metabolite sensors and biopotential electrodes for electrophysiological recordings. Moreover, we demonstrate real world applications with alternative bodily fluids to blood, such as sweat enabling non-invasive and continuous monitoring. Our proposed all-polymer “smart e-skin multisensor” which is fully printed on top of commercial tattoo electrodes paves the way toward next generation multiparameter sensing wearable biomedical devices that can efficiently interface the human skin without compromising their performance and mostly interestingly without causing any adverse effects to the skin.
11:15 AM - BM09.01.08
Touchless Omnidirectional Magnetosensitive Skins for Interactive Electronics
Gilbert Santiago Canon Bermudez 1 , Juergen Fassbender 1 , Denys Makarov 1
1 , Helmholtz-Zentrum Dresden, Dresden Germany
Show AbstractThe widespread permeation of electronic devices into our daily life has increased the importance of seamless interaction schemes that simplify the user’s experience. Electronic skins [1-3] contribute naturally to this development by combining sensor [4,5] and actuator elements in a compliant and mechanically imperceptible [6] format, thus eliminating the need for rigid interfaces. To advance beyond the conventional tactile interactions, we have recently proposed magnetosensitive skins [7-10] as a novel way to interact with objects in a touchless manner. This vision implies that basic building blocks of any interaction like pressing (proximity sensing) or turning (direction sensing) have to be replicated in a touchless format. In order to do so, our methodology utilizes magnetic fields as external stimuli to magnetosensitive circuits which provide a 3D reconstruction of motion in space. Moreover, to expand the breadth of applications, these interactive devices should operate over the whole range of typically available magnetic fields, spanning from the geomagnetic field of 40 µT up to regular permanent magnet fields of ~10 mT.
Here, we introduce a technology platform that addresses this vision to extend the potential of magnetosensitive skins. At its core, the platform utilizes metallic thin films as magnetoresistive (MR) and Hall-effect sensor elements, which are prepared on 6-µm-thick polymeric foils. This combination of out-of-plane (Hall) and in-plane (MR) sensors allows omnidirectional sensing on a single substrate. In addition, by using geometrical modifications like barber poles [11] or measurement schemes like zero-offset anomalous Hall magnetometry [12,13], the output sensitivity and offset can be optimized for a wide variety of applications.
We foresee that these highly compliant magnetic skins could be used to digitize fine motion, e.g. fingers with respect to the palm. This feat could enable the integration of usually rigid magnetic detection systems into on-skin, textile-based or Internet of Things (IoT) applications. A successful implementation could lead to a new class of virtual or augmented reality systems and interactive input devices which extract information from their surroundings through magnetic tags.
[1] T. Someya et al., Proc. Natl. Acad. Sci. U. S. A. 101, 9966 (2004).
[2] D. H. Kim et al., Science 333, 838 (2011).
[3] S. Bauer et al., Adv. Mater. 26 149 (2014)
[4] S. Lee et al., Nature Nanotechnology 11, 472 (2016).
[5] X. Ren et al., Adv. Mater. 28, 4832 (2016).
[6] M. Kaltenbrunner et al., Nature 499, 458 (2013).
[7] M. Melzer, DM et al., Nature Commun. 6, 6080 (2015).
[8] M. Melzer et al., Adv. Mater. 27, 1274 (2015).
[9] N. Münzenrieder et al., Adv. Electron. Mater. 2, 1600188 (2016).
[10] D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016).
[11] Phillips Semicond., Electronic Compass Design using KMZ51 and KMZ52, (2000).
[12] T. Kosub et al. Phys. Rev. Lett. 115, 097201 (2015)
[13] T. Kosub et al., Nat. Commun. 8, 13985 (2017).
11:30 AM - BM09.01.09
A Bioinspired E-Skin Able to Detect the Direction of Applied Pressure for Robotics
Clementine Boutry 1 , Marc Negre 2 , Mikael Jorda 2 , Orestis Vardoulis 2 , Alex Chortos 3 , Zhenan Bao 2
1 , EPFL, Geneva Switzerland, 2 , Stanford University, Stanford, California, United States, 3 , Harvard University, Cambridge, Massachusetts, United States
Show AbstractThe ability to sense mechanical normal and shear forces experienced by robot fingers in grasping and insertion tasks could dramatically improve the performances of chirurgical and industrial robotics, but is limited by the lack of suitable sensors. We present a new bio-inspired flexible electronic skin (e-skin) with high tactile sensitivity, which can detect the direction of applied forces and can be mounted on a robotic arm to control movements in high precision tasks.
The e-skin design mimics the configuration of human skin, where microstructures looking like hills and valleys, located between the outer epidermal and inner dermal layers of the skin, are known to amplify and transfer the tactile stimuli from the skin surface to mechanoreceptors located in the dermis.
Our e-skin consists of 3 layers laminated together, forming an array of capacitive sensors: 1) A bottom polyurethane layer with hills and valleys mimicking the human skin, 2) a thin dielectric layer used as spacer for the capacitors, and 3) a top polyurethane layer with an array of square pyramids. As presented earlier by our group, these microstructures allow the polyurethane to elastically deform when an external pressure is applied, storing and releasing the energy reversibly, thus minimizing undesirable viscoelastic behavior.
The flexible electrodes of our e-skin consist of carbon nanotubes (CNTs) spray-coated and patterned via photolithography on silicon substrates and transferred on the bottom and top polyurethane layers. Each hill, with a diameter of 1mm, is covered by an array of 5 x 5 = 25 pressure capacitive sensors (pixels).
Thanks to the 3D geometry of the hills, when a force with both normal and shear components is applied, the pixels located at one side of the hill will experience a higher pressure (and therefore capacitance variation) as compared to the pixels located on the other side, allowing for the detection of the direction of the applied pressure.
The high sensitivity of our e-skin (able to sense the pressure exerted by a 15mg mini bead that is half the weight of a sesame seed), robustness (negligible hysteresis and reproducible characteristics when pressures as high as 1.5MPa are applied), long-term stability (above 30,000 cycles) and fast response-time (in the millisecond range), allow its use in the control of a robotic arm, where complex tasks involving manipulation of fragile objects such as raspberries are demonstrated.
11:45 AM - BM09.01.10
Ultrathin, Highly Conformable Multimodal Sensor Based on Organic Field Effect Transistor for Tactile Sensing Applications
Fabrizio Antonio Viola 1 , Andrea Spanu 1 , Stefano Lai 1 , Annalisa Bonfiglio 1 , Piero Cosseddu 1
1 , University of Cagliari, Cagliari Italy
Show AbstractTo date, one of the most studied field of application of organic semiconductor-based devices is certainly the sensing field. In fact, organic sensors can be fabricated at low costs on unconventional, highly flexible, and possibly conformable substrates, and can be easily transferred onto clothes for the realization of wearable electronics, or even employed for the fabrication of electronic skin. Recently, a rising interest has been directed to the development of novel technologies for reproducing the sense of touch for a large set of possible applications such as prosthetics, human-robot interaction, and rehabilitation.
In this work we will show that highly-conformable, low voltage, tactile sensors, based on Organic Charge Modulated FETs (OCMFETs) can be fabricated and employed for monitoring at the same time pressure and temperature variations. Such devices can be fabricated on ultrathin, free standing, plastic films. We will demonstrate that such nanometric films can be deposited in a highly reliable way, over large areas, on a carrier substrate using cost efficient approaches either by liquid or vapor phase. After deposition, arrays of multimodal tactile sensors are fabricated on their surfaces using OCMFET architecture.
In order to obtain multimodal tactile transducers, a piezo and pyro-electric polymeric thin film, namely PVDF, is deposited by spin coating, and poled, directly on sensing area of the devices. In this way, when the temperature of the sensing area is changed, the charges induced in the pyroelectric film lead to a variation of the threshold voltage of the OCMFET and, consequently, of the transistor IDS. The proposed approach can be used for temperature monitoring within a range from 8-50 °C, which is the typical temperature range requested for tactile applications. Thanks to the piezoelectric property of the PVDF it is also possible to obtain a threshold voltage shift in response to a mechanical stimulus exerted onto the PVDF, thus obtaining, a modulation of the output current IDS. A detailed dynamic electromechanical characterization has been carried out, showing that such devices are able to detect dynamic stimuli at a frequency up to 500 Hz and we will demonstrate that such devices can detect very small pressure, below 300 Pa and can detect forces within a range from 0.01 up to 5 N.
Interestingly enough, after the arrays of sensors are fabricated, such ultrathin sensorised films can be peeled off out of the carrier substrate, and conformably transferred onto any other kind of surfaces. For instance we will demonstrate that they can be directly transferred onto the human skin for the local monitoring of applied pressure and temperature variations.
The highly flexibility of the developed structure, and the easiness of the employed process, make this solution very interesting for the fabrication of multimodal, highly compliant artificial skin.
BM09.02: Materials I
Session Chairs
Anastasia Elias
Ingrid Graz
Ivan Minev
Monday PM, November 27, 2017
Sheraton, 2nd Floor, Republic B
1:30 PM - *BM09.02.01
Oxide Based Transparent Stretchable Electronics and Sensors
Philipp Gutruf 1 2 , Sumeet Walia 1 , Sharath Sriram 1 , Madhu Bhaskaran 1
1 School of Engineering, RMIT University, Melbourne, Victoria, Australia, 2 Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois, United States
Show AbstractIntroduction: Electronic devices are pervasive, with smartphones and wearable devices becoming the norm. The industry trend is towards lighter, energy efficient, and durable devices. Stretchable electronics, especially those that are wearable, is where the solution lies. Stretchable electronic devices are used in numerous applications ranging from electronics, energy, and healthcare. Integration of multifunctional oxide thin layers in stretchable devices would create enhanced functionality and performance. This integration has been limited by the brittle nature of oxides and high temperature processing requirements. In this work, we demonstrate the integration of multifunctional metal oxides on a prevalent, biocompatible, stretchable substrate, polydimethylsiloxane (PDMS). We exploit the microtectonic surface structure of the oxide thin films that is uniquely obtained on stretchable substrates, to demonstrate high performance sensing and optical devices.
Results and Discussion: A unique, repeatable and scalable transfer process was demonstrated with indium tin oxide and silicone rubber. The process relies on the poor adhesion of platinum to silicon which allows high temperature oxide thin films to be deposited and defined with standard micro and nano fabrication techniques and subsequently peeled-off using PDMS. The microtectonic phenomena govern the stretchability of the thin oxide films. This phenomena occurs when thin, brittle oxide films are incorporated into elastomeric films, the brittle oxide layer forms micrometer-sized plates which overlap and slide over each other. This allowed for the realization of stretchable transparent electronics which could be stretched up to 15%.
The versatility of the technique was tested with a different oxide material, zinc oxide. This allowed for the demonstration of gas and UV sensors which are also transparent and biocompatible. These stretchable devices outperformed their rigid counterparts with enhanced sensitivity (>20%) at room temperature. The sensors were capable of detecting gases such as hydrogen and nitrogen dioxide. The photosensitive property was tapped in to realize highly sensitive UV sensors.
For applications in optics, materials which have a high refractive index contrast are desired with the ability to create nano-patterns. The transfer technique was utilised to create nano-patterned titanium dioxide based stretchable devices to create dielectric grating and resonant photonic devices – these serve as fundamental building blocks for tunable optics. The devices exhibit excellent linear tunability alongside with an accurate representation of local strain.
Conclusion: The ability to combine a high temperature processed oxide material with a stretchable polymeric base with exceptionally high stretchability unleashes multifaceted possibilities for advanced applications. The versatility of this technique has been demonstrated for various areas of research such as electronics, optics and photonics.
2:00 PM - BM09.02.02
Device Optimization of Intrinsically Stretchable All-Carbon Transistors with Non-Polar Dielectrics for Robust and Hysteresis-Free Operation
Alex Chortos 1 , Chenxin Zhu 2 , Jin Young Oh 1 , Zhenan Bao 1
1 Chemical Engineering, Stanford University, Stanford, California, United States, 2 Electrical Engineering, Stanford University, Stanford, California, United States
Show AbstractIntrinsically stretchable electronics are promising for applications in wearable electronics, novel consumer devices, and bio-integrated electronics because of their compatibility with full areal device coverage and low-cost fabrication techniques. Networks of carbon nanotubes (CNTs) are uniquely suitable for intrinsically stretchable devices because they show excellent stretchability and durability as well as high mobilities. Many of the previous stretchable devices fabricated with CNT semiconductors utilize dielectrics with ionic polarization, which limits the time response. In this work, we investigate the challenges and limiting factors associated with preparing intrinsically stretchable all-carbon transistors using non-polar dielectrics. The non-polar nature of the dielectrics results in negligible hysteresis as well as good bias stress behavior and threshold voltages close to 0 V.; processing limitations of the nonpolar dielectric material limit the areal capacitance to <2 nF/cm2. With such a low areal capacitance, changes in the doping state of the CNTs can cause large shifts in the threshold voltage, which would lead to the requirement for large gate voltages to turn on or off the transistor. Consequently, this near-zero threshold voltage is important for enabling devices that can operate at voltages <15 V, despite the low areal capacitance.
Compared to stretchable devices with nonpolar dielectrics, rigid control devices made with highly polar silicon dioxide dielectrics exhibit mobilities that are several times higher. This is because the polar groups on the silicon dioxide p-dope the CNT semiconductor and attract water that acts as additional p-type dopants. Consequently, while the nonpolar stretchable dielectric enables hysteresis-free device characteristics, it also limits the mobility. Characterization of device performance as a function of dielectric thickness showed that large-bandgap CNTs exhibited mobility values that were highly dependent on the dielectric thickness, indicating trap-limited behavior. This observation was confirmed with temperature-dependent measurements showing that the stretchable devices with large bandgap semiconductors exhibited highly non-ideal transfer curves and typical trap-limited temperature dependence. While devices with large bandgap CNT semiconductors were limited by traps, devices with small bandgap CNT semiconductors exhibited much larger currents, and were consequently often limited by contact resistance. The effect of dielectric thickness and contact resistance had important consequences for the strain-dependent performance of the devices, allowing the identification of ideal CNT semiconductor characteristics for robust and hysteresis-free stretchable transistors.
2:15 PM - BM09.02.03
A New Flexible Substrate Structure to Use Brittle Conductors in Flexible Electronics
Seongmin Park 1 , Hyuk Park 1 , Yoonyoung Chung 1
1 Electrical Engineering, Pohang University of Science and Technology, Pohang, Gyeongsangbuk-do, Korea (the Republic of)
Show AbstractWe propose a novel method to use brittle conducting layers in flexible electronics. Flexible conducting materials, such as polymers, graphene, and carbon nanotube, did not exhibit high conductivity enough to be used in commercial electronics widely. To achieve both low resistance and high flexibility, we utilized a conventional metal thin film and a strain absorbing layer inside a flexible substrate. The strain absorbing layer can effectively reduce a mechanical stress applied to the metal layer when bent; thus, brittle metal thin film, such as Indium Tin Oxide (ITO), can withstand higher bending stress with this approach than the conventional structure. A metal layer on conventional flexible substrate exhibited a large resistance increase about four times after sequential bending and releasing, while our novel flexible substrate structure reduces the resistance change drastically by less than 20%.
2:30 PM - BM09.02.04
An Ultrathin Epidermal Strain Sensor Constructed with an Inkjet-Printed Conductive Polymer on an Elastomer Nanosheet
Kento Yamagishi 1 , Yuma Tetsu 1 , Akira Kato 2 , Yuya Matsumoto 2 , Mariko Tsukune 2 , Yo Kobayashi 3 4 , Masakatsu Fujie 3 , Shinji Takeoka 1 , Toshinori Fujie 4 5
1 Graduate School of Advanced Science and Engineering, Waseda University, Shinjuku, Tokyo, Japan, 2 Graduate School of Creative Science and Engineering, Waseda University, Shinjuku, Tokyo, Japan, 3 Future Robotics Organization, Waseda University, Shinjuku, Tokyo, Japan, 4 , JST PRESTO, Kawaguchi, Saitama, Japan, 5 Waseda Institute for Advanced Study, Waseda University, Shinjuku, Tokyo, Japan
Show AbstractPhysical conformability to the epidermal structure is critical to minimize the interference that skin-contact devices cause to natural skin deformation. Here, we developed an ultrathin strain sensor constructed with an inkjet-printed conductive polymer, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) on an elastomer nanosheet made from polystyrene-polybutadiene-polystyrene (SBS). We demonstrated that the SBS nanosheet (thickness: 321 nm) merely interfered with natural skin deformation because of its ultrathin structure and glue-free conformable adhesion, which minimized the inhibition of the extension of skin grooves. The sandwiched SBS/PEDOT:PSS/SBS strain sensor, whose total thickness was ~1 μm, deeply followed and physically conformed to the human skin surface without using any adhesive agents. The ultrathin sensor showed the strain-dependent resistance change with a gauge factor of 0.73 ± 0.10 at 0–6% strain. The normalized resistance of the sensor exhibited a repeatable linear change corresponding to 0–2% strain even after more than 10 cycles. We successfully measured the small skin strain (~2%) on a forearm using the ultrathin epidermal strain sensor while extending the wrist joint. Such an epidermal strain sensor will be a powerful tool for precisely detecting the motion of human skin as well as artificial soft-robotic skin.
2:45 PM - BM09.02.05
Deformable Organic Nanowire Field-Effect Transistor
Yeongjun Lee 1 2 , Jin Young Oh 2 , Taeho Roy Kim 2 , Xiaodan Gu 2 , Yeongin Kim 2 , Nathan Wang 2 , Hung-Chin Wu 2 , Raphael Pfattner 2 , John W.F. To 2 , Toru Katsumata 2 , Donghee Son 2 , Jiheong Kang 2 , Jeffery B.-H. Tok 2 , Tae-Woo Lee 3 , Zhenan Bao 2
1 , POSTECH, Pohang Korea (the Republic of), 2 , Stanford University, Stanford, California, United States, 3 , Seoul National University, Seoul Korea (the Republic of)
Show AbstractDeformable electronic devices impervious to mechanical influence when mounted on the surface of dynamically-changing soft matter have great potential for next-generation implantable bioelectronic devices. Here, we present a deformable organic semiconducting (OSC) nanowire (NW), composed of diketopyrrolopyrrole (DPP)-based polymer semiconductor and high-molecular-weight polyethylene oxide (PEO) as a molecular binder for electrospinning. We achieved a deformable OSC NW field-effect transistor (FET). Our obtained electrospun OSC NW showed high field-effect mobility > 8 cm2V-1s-1 in a conventional FET geometry with high-k polymer dielectric, and can also be easily deformed by applied strains (both 100% tensile and compressive strains). Furthermore, the mechanical durability of NW can also be significantly increased by simply re-engineering the geometric structure of the deformable OSC NW. Our fully-deformable OSC NW FET withstood 100% uniaxial stretching with minimal change of electrical properties, even after a 3D volume change (> 1700% and back to original state) of a rubber balloon. The deformable transistor robustly operated on a mechanically-dynamic soft matter surface e.g. a pulsating balloon that mimics a beating animal heart, which demonstrates potential of the deformable transistor for future biomedical applications.
3:30 PM - *BM09.02.06
Soft Devices—Perspectives
Siegfried Bauer 1
1 , Johannes Kepler University Linz, Linz Austria
Show AbstractScientists are exploring elastic and soft forms of electronic skin, soft robots and energy harvesters, dreaming to mimic nature and to enable novel applications in wide ranging fields, from consumer and mobile appliances to biomedical systems, sports and healthcare. Antagonistic materials with a wide range of mechanical, physical and chemical properties are employed, from liquids and gels to organic and inorganic solids. Combining such a diversity of materials into unctionalities never seen before, is an ideal playground for research in mechanics. In the presentation I will first introduce latest research examples in sensor skin development and discuss ultra-flexible electronic circuits, light emitting diodes and solar cells as examples. Additional functionalities of sensor skin, such as visual sensors inspired by animal eyes, camouflage, self-cleaning and healing and on-skin energy storage and generation are briefly reviewed. I will then proceed to discuss soft robots which allow actuation with distributed degrees of freedom. We show that different actuation mechanisms lead to similar actuators, capable of complex and smooth movements in 3d space. Drawing inspiration from well known mechanical instabilities, such as snap-buckling and snap-through transitions can be harnessed to achieve high speed, large stroke soft actuators. Finally, I will discuss a paradigm change in energy harvesting, away from hard energy generators to soft ones based on dielectric elastomers. Such systems are shown to work with high energy of conversion, making them potentially interesting for harvesting mechanical energy from human gait, winds and ocean waves. All of the examples chosen demonstrate the importance of research that highlights the role of mechanics in multi-disciplinary areas across materials science, physics, chemistry, biology, medicine and engineering.
4:00 PM - BM09.02.07
Fabrication of Micro-Sized Stacked Dielectric Elastomer Actuator Arrays via Injection Molding
Mert Corbaci 1 , Kathleen Lamkin-Kennard 1 , Wayne Walter 1
1 , Rochester Inst of Technology, Rochester, New York, United States
Show AbstractDielectric elastomer actuators (DEAs) are known for their fast response, flexibility, lightweight, and high strain rates. Due to their working mechanism, DEAs require high voltage inputs (in the range of a few kilovolts), which renders DEAs inefficient compared to their alternatives and poses a danger for interacting with the environment. Fundamentally, decreasing the size of DEAs can reduce the voltage requirement down to safer voltage ranges, however, there are two major problems associated with miniaturizing DEAs. Firstly, the strain and the power outputs go down as the size of a DEA decreases. Secondly, conventional fabrication methods are not suitable for making stand-alone DEA structures in micro-scale. To compensate for the decrease in output parameters, multiple layers of DEAs can be stacked up to form larger structures composed of smaller DEA units.
In an earlier study, a fabrication process was introduced for making stacked DEAs in micro-scale, which had a poor repeatability because it relied on human precision. This study, introduces a fabrication method for making micro-sized DEAs using injection molding, decreasing the effect of human precision on the repeatability of the fabrication process. Dielectric and conductive layers were made of poly(dimethylsiloxane) (PDMS) and a composite of multi-walled carbon nanotubes (CNTs) and (PDMS), respectively. Conventional soft lithography methods were used for forming the dielectric stacked layers in micro-scale. Conductive composite material was then injected into the dielectric structure. Free standing DEAs were fabricated and tested for actuation ratio with different voltage inputs.
4:15 PM - BM09.02.08
Graphene Based Hybrid Electrodes for Multilayered Dielectric Elastomer Actuators
Mihai Duduta 1 , Ehsan Hajiesmaili 1 , Kezi Cheng 1 , Robert Wood 1 , David Clarke 1
1 , Harvard University, Cambridge, Massachusetts, United States
Show AbstractDielectric elastomer actuators (DEAs) are one of the most promising technologies for soft robotics. As compliant capacitors, DEAs are capable of rapid deformation under an applied electric field, giving them an inherent advantage over pneumatic or hydraulic driven soft actuators. One of the main challenges in developing robust, high energy density DEAs has been finding a suitable electrode which matches the elongation of the elastomer without adding significant stiffness to the device. Some of the best electrode materials include nanoscale high aspect ratio conductors, such as single walled carbon nanotubes (SWCNTs) and silver nanowires (AgNW). However, while their high aspect ratio is well suited for creating percolating networks, it also reduces the amount of area coverage of the elastomer. The resulting devices show high conductivity under stretch, but low capacitances and force outputs relative to the predicted values based on material properties and applied electric field. Our solution to the low area coverage is to include few layer graphene particles to ensure a greater section of the elastomer is in contact with a conductive particle. Graphene flakes have a unique 2D structure and can be stabilized in water using surfactants such as sodium cholate. These properties make them suitable for use in multilayered dielectric elastomers, where each electrode needs to be spin coated, sprayed or stamped for high throughput. Exfoliated graphene flakes were layered with our UV curable acrylic elastomers to make bending DEAs. Early results show that graphene flakes provide 3-7x more area coverage compared to pure SWCNTs. The lack of high aspect ratio particles limits the in plane conductivity, which can be addressed by blending graphene flakes with either SWCNTs or AgNWs. Impedance measurements at 400 kHz show the AgNW blends boost capacitance by 2-10x. Force measurements at constant applied field will be used to determine the best performing electrode materials.
4:30 PM - BM09.02.09
Buckled Elastomer Foams and Their Application in Pneumatic, Soft Machines
Benjamin Mac Murray 1 , Robert Shepherd 1
1 , Cornell University, Ithaca, New York, United States
Show AbstractOpen-celled elastomer foams have enabled many new fluidically inflated, soft machine designs. These foams allow for the simple fabrication of complex 3D shapes with an intrinsically embedded fluidic network for inflation, without the requirement of complex molding or assembly that is necessary with other soft machine fabrication methods.
The actuation of foam-based machines is often limited by the relatively modest ultimate elongation of elastomer foams. Here, we address this limitation by exploring the use of buckled foam actuators. Using the inherent foam void space, we process these structues to impart residual strain, which we show can be beneficial to actuation. The residual strain increases the overall apparent extension in tension prior to failure. We performed X-ray micro-computed tomography imaging to confirm that the pore network remains largely open, even under considerable compressive strain. When we integrated these compressed foams in inflatable actuators, the buckled foams exhibited augmented actuation over non-compressed foams by providing either a greater force or a larger displacement for a given inflation pressure. We attribute the augmented actuation to the asymmetric stress-strain behavior in compression and tension that is unique to elastomer foams.
We will discuss two applications for the buckled foams: a cardiac assist device and shape morphing gaming controller.
We designed and fabricated a unique Direct Cardiac Compression device, a type of implanted, mechanical circulatory support, that applies pressure to the exterior of the heart to aid in blood flow. In our device, the high porosity of the foam actuators allowed rapid inflation and deflation cycling at physiological rates (120 beats per minute). By incorporating buckling into the foam actuators, we achieved a large volume displacement upon inflation (ΔV ~ 70 mL per chamber) from an initially thin device thickness (d ~ 15 mm). Finally, because the major components of the device were liquid-processable elastomers and foams, we demonstrated that the device can be fabricated in a patient-specific shape using custom 3D printed molds designed from standard clinical imaging methods including MRI and CT. In ex vivo tests, the device formed a tight fit surrounding a model porcine heart and pumped fluid at physiologically relevant frequencies.
We will also present our latest results developing an elastomer lattice-based soft controller for virtual- and augmented-reality applications. This controller also exploits the unique properties of cellular elastomers to attain unique, shape morphing behavior.
4:45 PM - BM09.02.10
Development of Low-Voltage High-Deformation Carbon Nanotube Based Electrothermal Actuator with Uncurling Ability
Yu-Chen Sun 1 2 3 , Benjamin Leaker 1 2 3 , Hani Naguib 1 2 3
1 Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada, 2 Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario, Canada, 3 Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
Show AbstractArtificial muscles offer a number of advantages over traditional actuators, including high flexibility and low weight. Among different types of artificial muscle materials, electrothermal actuators (ETAs) are one of the most promising solutions due to low input voltage and high deformation ability. However, there are many challenges that still need to be overcome before these materials can be applied to practical applications. ETAs are active materials that can generate different motions via thermal expansion induced from Joule heating. The degree of expansion, which influences the deformation, is determined by the coefficient of thermal expansion (CTE) of the material. In order for Joule heating to take place, it is necessary to create a conductive network that can interface with a polymeric matrix. One of the most common methods for creating ETAs is to insert fillers with high electrical and thermal conductivity into the polymer. Such network structure provides the necessary Joule heating for actuation and allows for fast and uniform heat distribution throughout the material. The current best reported ETA relies on super-aligned carbon nanotube (CNT) buckypaper. These ETAs offer a very high performance but cannot be easily produced due to the complex fabrication procedure associated with super-aligned buckypapers. In this study, we present the design of a randomly oriented CNT ETA that has extremely high deformation capability when subjected to a low input voltage. A maximum tip deformation of 19.3 mm can be achieved by a 28 mm length U-shape ETA under 12V. We also introduce a novel technique for inducing U-shaped ETAs into a curled resting state configuration. In this configuration, the ETA can achieve 540° uncurling bending angle under 12V , significantly larger than any previously reported ETA. The improved deformation and manufacturability of our actuator will help to further the development of ETAs and assist with the transition from the research lab to real world applications.
Symposium Organizers
Ingrid Graz, Johannes Kepler University Linz
Anastasia Elias, University of Alberta
Ivan Minev, Technische Universität Dresden
Benjamin O'Brien, StretchSense
BM09.03/BM07.04/BM08.03: Joint Session I: Flexible and Stretchable Electronics for Neural Interfaces
Session Chairs
Christelle Prinz
Bozhi Tian
Tuesday AM, November 28, 2017
Sheraton, 2nd Floor, Grand Ballroom
8:30 AM - *BM09.03.01/BM07.04.01/BM08.03.01
Soft and Stretchable Epidermal Electronics and Biosensors for Personalized Medicine
Roozbeh Ghaffari 1
1 Center for Bio-Integrated Electronics, Simpson Querrey Institute for BioNanotechnology, Northwestern University, Evanston, Illinois, United States
Show AbstractSoft bioelectronics systems enabled by recent advances in materials science are approaching the softness and curvilinear format of human skin. These systems are referred to as 'epidermal electronics' by virtue of their stretchable form factors and 'skin-like' mechanics compared to conventional packaged electronics and sensors. Here we present recent results for an emerging class of fully-integrated epidermal electronics. These devices incorporate arrays of sensors, microprocessors, memory and wireless connection (via Bluetooth low energy) configured in ultrathin, stretchable formats for continuous monitoring of neuromuscular and biomechanics signals. Quantitative analyses of strain distributions and circuit performances under mechanical stress highlight the utility of these systems in clinical operating rooms or in the home. We conclude with pilot clinical studies showing the utility of these epidermal systems in neurophysiological monitoring compared to clinical standards of care in operating rooms.
9:00 AM - BM09.03.02/BM07.04.02/BM08.03.02
Syringe-Injectable Mesh Electronics Integrate Seamlessly with Minimal Chronic Immune Response in Central Nervous System
Tao Zhou 1 , Guosong Hong 1 , Tian-Ming Fu 1 , Xiao Yang 1 , Robert D. Viveros 1 , Charles M. Lieber 1
1 , Harvard University, Cambridge, Massachusetts, United States
Show AbstractSeamless integration of minimally-invasive electrical probes into animal tissues is of central importance to both neuroscience research and biomedical applications. Previously we designed ultra-flexible mesh electronics that can be injected into animal brains through syringes. Here we report systematic histology studies of the interface between ultra-flexible mesh electronics and central nervous system. We also conducted histology studies of conventional electrical probes implanted in mice brain for comparison. Compared with conventional electrical probes, mesh electronics introduces little or no inflammation to brain tissues after chronic implantation. Unlike conventional rigid probes, which introduce depletion regions in brain tissues, neurons and axons surrounding the mesh electronics exist at endogenous tissue levels. More intriguingly, axons and neuron somata even penetrate into the interior of mesh electronics, allowing for the formation of seamless interfaces between brain tissues and mesh electronics. Seamless incorporation of minimum invasive ultra-flexible mesh electronics with tissues allows for a wide range of applications, including recordings, stimulation and repairing of the brain and other tissues such as spinal cord, opening a new window for brain-machine interfaces and cyborg animals.
9:15 AM - BM09.03.03/BM07.04.03/BM08.03.03
Dynamic Devices for Neural Interfacing
Christopher Proctor 1 , Vincenzo Curto 1 , Jolien Pas 1 , Adam Williamson 2 , George Malliaras 1
1 , Ecole des Mines St Etienne, Santa Barbara, California, United States, 2 , Aix Marseille University, Marseille France
Show AbstractSignificant advances have been made in the last two decades in interfacing electronic devices with the nervous system. Organic electronic materials in particular have emerged as ideal materials for interfacing with the brain due to their flexibility, biocompatibility and moreover their electronic and ionic conductivity. To that end, significant research efforts are being pursued to develop minimally invasive, implantable organic electronic devices integrating recording, stimulating, and drug delivery features. Here we report recent developments towards such dynamic devices for neural interfacing that take full advantage of the favorable properties offered by conducting polymers and polymer substrates. It is shown that thin, flexible devices can incorporate microfluidic channels to enable new sensing and therapeutic functionalities. Furthermore we show such features also open the door to novel implantation strategies that can reduce inflammatory tissue response as well as the surgical footprint required for implantation. We anticipate this work will accelerate the development of a new generation of devices for neural interfacing.
10:00 AM - BM09.03.04/BM07.04.04/BM08.03.04
Microfluidic Actuation of Flexible Microelectrodes for Neural Recording
Daniel Vercosa 2 3 , Flavia Vitale 1 , Alex Rodriguez 3 , Sushma Sri Pamulapati 1 , Frederik Seibt 4 , Eric Lewis 3 , Stephen Yan 5 , Krishna Badhiwala 5 , Mohammed Adnan 1 , Micheal Beierlein 4 , Caleb Kemere 3 5 6 , Matteo Pasquali 1 7 , Jacob Robinson 3 2 5
2 Applied Physics Program, Rice University, Houston, Texas, United States, 3 Department of Electrical and Computer Engineering, Rice University, Houston, Texas, United States, 1 Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas, United States, 4 Department of Neurobiology and Anatomy, McGovern Medical School at UTHealth, Houston, Texas, United States, 5 Department of Bioengineering, Rice University, Houston, Texas, United States, 6 Department of Neuroscience, Baylor College of Medicine, Houston, Texas, United States, 7 Department of Chemistry, The Smalley-Curl Institute, Rice University, Houston, Texas, United States
Show AbstractNew tools for the recording and stimulation of neurons are key to advancing basic neuroscience research and developing new treatments for neural dysfunction. Despite tremendous advances, chronic electrodes for high-resolution electrical recording and modulation of neural activity at the cellular level still rely on rigid metal or silicon materials, which poorly match soft brain tissue and cause extensive acute and chronic injury, eventually leading to electrode encapsulation and the loss of signal over the scale of weeks or months.
Flexible electrodes and ultra-small microwires have been shown to significantly reduce brain damage during chronic implantation and increase the quality and longevity of neural recordings compared to rigid electrodes. However, unsupported flexible electrodes easily buckle on contact with the brain and require temporary stiffening agents to overcome the force of implantation. These agents increase the device footprint and may cause additional damage to the brain during implantation.
Here, we present the microfluidic drive, a novel solution to precisely actuate and implant flexible electrodes without changing the profile of the implanted electrode. After constructing a multi-layer polydimethylsiloxane (PDMS) microfluidic device to constrain electrodes, we utilize viscous fluid flow to push electrodes into tissue. The viscous fluid distributes force along the length of the electrode, allowing it to enter the brain without buckling. Computational analysis on electrodes made from flexible carbon nanotube fibers (CNTfs) suggests that implantation using the microfluidic drive increases the critical buckling force of CNTf microelectrodes by three-fold compared to standard methods.
The device’s hydraulic design with embedded valves enables precise control of the electrode position with minimum fluid output. In vitro experiments in brain phantoms show that microfluidic actuated CNTf electrodes can be implanted up to a 4-mm depth with 30 µm precision, while keeping the total volume of fluid ejected with the electrode below 0.5 µL.
10:15 AM - BM09.03.05/BM07.04.05/BM08.03.05
Hybrid Integration of Stiff Active Electronic Components on Stretchable Carrier Substrate
Florian Fallegger 1 , Aaron Gerratt 1 , Stephanie Lacour 1
1 , Bertarelli Foundation Chair in Neuroprosthetic Technology, Laboratory for Soft Bioelectronic Interfaces, Centre for Neuroprosthetics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne Switzerland
Show AbstractMost implantable neuroprostheses consist of electrodes reading neural signals and/or stimulating the neural tissues. These sites are usually treated as passive components in the system with raw signals treatment and logic processing being traditionally performed by external electronic circuits. To increase electrode density and signal bandwidth, closer integration of electronic hardware is being explored.
Here, we explore how to integrate (CMOS) active electronic components with soft surface electrodes embedded in thin silicone membranes. This hybrid integration combines conventional microfabrication techniques with innovative polymer processing techniques. The system consists of three main parts to enable the transition from the hard components to the stretchable substrate: the chip integrated with a soft via material, a stiff platform to isolate the component and contacts area from strain, and stretchable interconnects.
The hard components are picked and placed manually or semi-automatically and then embedded in a PDMS matrix. The stiff platform consists of 150μm thick SU8 disk integrated under the chips. The components are electrically contacted with a “soft via” consisting of a composite of platinum microparticles and PDMS, self-aligned to the contacts by screen-printing. Interconnects consist of stretchable gold thin films patterned by shadow masking then assembled in a multilayer structure in order to achieve simple circuits. The different layers (i.e. CMOS Integrated chip, soft vias and multiple layers of interconnects) are aligned and bonded using a custom-made alignment tool.
The hybrid circuit is characterized mechanically up to global uni-axial strain of 30% showing that the stiff components do not experience local strain greater than 0.2%. Furthermore the strain profile at the surface of the circuit, running from the mechanically-isolated rigid chips to the fully stretchable carrier is smooth suppressing any peak strain at the rigid-elastic interface. The developed method allows contacting thin (< 250μm) but rigid chips with contact sites with sizes in the range of 100μm to 100s μm. This system enables functions such as multiplexing or addressing individual electrode sites with a switch matrix scheme, which will allow for an increase in the number of electrode sites.
10:30 AM - BM09.03.06/BM07.04.06/BM08.03.06
Three-Dimensional Silicon Mesostructures for Biointerfaces
Yuanwen Jiang 1 , Bozhi Tian 1
1 , University of Chicago, Chicago, Illinois, United States
Show AbstractSilicon-based materials exhibit biocompatibility, biodegradability as well as a spectrum of important electrical, optical, thermal and mechanical properties, leading to their potential applications in biophysical or biomedical research. However, existing forms of silicon (Si) materials have been primarily focused on one-dimensional (1D) nanowires and two-dimensional (2D) membranes. Si with three-dimensional (3D) mesoscale features has been an emerging class of materials with potentially unique physical properties. Here, we incorporated new design elements in traditional synthetic methods to prepare various forms of 3D Si mesostructures and studied their functional biointerfaces with cellular components. In the first example, an anisotropic Si mesostructure, fabricated from atomic gold-enabled 3D lithography, displayed enhanced mesoscale interfacial interactions with extracellular matrix network. This topographically-enabled adhesive biointerface could be exploited for building tight junctions between bioelectronics devices and biological tissues. Another Si mesostructure with multi-scale structural and chemical heterogeneities, was adopted to establish a remotely-controlled lipid-supported bioelectric interface. We further adapted the bioelectric interface into the non-genetic optical modulation of single dorsal root ganglia neuron electrophysiology dynamics. Our results suggest that the dimensional extension of existing forms of Si could open up new opportunities in the research of biomaterials manufacturing and application.
10:45 AM - BM09.03.07/BM07.04.07/BM08.03.07
Wireless Photometers for In Vivo Behavioral Studies in the Deep Brain
Luyao Lu 1 , Philipp Gutruf 1 , Li Xia 2 , Dionnet Bhatti 2 , Michael Bruchas 2 , John Rogers 1
1 , Northwestern University, Evanstan, Illinois, United States, 2 , Washington University in St. Louis, St Louis, Missouri, United States
Show AbstractMonitoring the neural dynamics at the cellular level in behaving animals is a central goal of modern neuroscience. This is critical to understand neural computations and communications that create diverse brain functions. Current Ca imaging techniques such as fiber photometry provides some capabilities for recording neuron activities in animals during behaviors. However, the rigid optical fibers are not mechanically compliant with soft brain tissues, and the wired set up will restrict movements of animals, therefore impeding studies of natural behaviors. Here we present an integrated wireless photometry device capable of recording calcium transient activity in awake, freely behaving animals. The wireless photometry platform consists of a microscale inorganic light-emitting diode (μ-ILED) and a microscale inorganic photodetector (μ-IPD) for stimulating and recording Ca fluorescence, a detachable transponder, a control unit, a miniature power supply and an external receiver system. These μ-ILED and μ-IPD mount on ultrathin, flexible kapton substrate with overall dimensions (~350 μm wide and ~150 μm thick) significantly smaller than fiber optic cables. The wireless data transmission fully eliminates physical tethers and reduces motion artifacts. Detailed in vivo studies demonstrate that the wireless photometry platform allows high fidelity recording of calcium fluorescence in the deep brain, with results that are comparable or better than those obtained from fiber photometry system.
11:00 AM - *BM09.03.08/BM07.04.08/BM08.03.08
Wireless, Implantable Optoelectronics for Stimulating, Inhibiting and Monitoring Neuronal Dynamics in the Deep Brain
John Rogers 1
1 , Northwestern University, Evanston, Illinois, United States
Show AbstractThe recent development of materials and design designs for flexible, filamentary optoelectronic probes opens up opportunities for wireless stimulation, inhibition and monitoring of neuronal dynamics in the deep brain regions of freely-moving, untethered animals. This talk summarizes some of the latest results in this field of research, with a focus on fluorescence photometers that integrate sub-mm scale light sources and photodetectors on narrow, needle-shaped polymer supports, suitable for delivery into the brain at sites of interest. The ultrathin geometry and compliant mechanics of these probes allow minimally invasive implantation and stable chronic operation. In vivo studies in freely moving animals demonstrate high fidelity recording of calcium fluorescence in the deep brain, with measurement characteristics that match or exceed those associated with the most advanced, tethered fiber photometry systems. The capabilities in optical recordings of neural dynamics in untethered, freely moving animals have potential for widespread applications in neuroscience research.
BM09.04/BM07.05/BM08.04: Joint Session II: Conductive Polymers for Biointerfaces
Session Chairs
Polina Anikeeva
Anastasia Elias
Tuesday PM, November 28, 2017
Sheraton, 2nd Floor, Grand Ballroom
1:30 PM - *BM09.04.01/BM07.05.01/BM08.04.01
Skin-Inspired Electronic Materials and Devices
Zhenan Bao 1
1 , Stanford University, Stanford, California, United States
Show Abstract
Flexible organic electronics have attracted considerable attention over the past decade. Stretchable electronics represent another type of optoelectronic devices that are intrinsically elastic, that is they are foldable, twistable, and stretchable while maintaining performance, integrity and durability. Incorporated into devices, properly designed stretchable materials may result in more robust devices under bending and strain compared to flexible but not stretchable materials. For intrinsically stretchable electronics, it is desirable to have intrinsically stretchable materials, ranging from stretchable conductors, stretchable dielectric to stretchable semiconductors. In this talk, I will present various molecular design concepts for realizing stretchable electronic polymers without compromising electronic properties. Some applications of such materials will also be presented.
2:00 PM - BM09.04.02/BM07.05.02/BM08.04.02
Measuring Evoked Electrocorticography on Cortical Surface of Optogenetics Rat Using Transparent Organic Electro Chemical Transistors
Wonryung Lee 1 , Dongmin Kim 1 , Naoji Matsuhisa 1 , Masaki Sekino 1 , Tomoyuki Yokota 1 , George Malliaras 2 , Takao Someya 1
1 , The University of Tokyo, Tokyo Japan, 2 Department of Bioelectronics, Ecole Nationale Supérieure des Mines, Gardanne France
Show AbstractOptogenetics tools have been developed to control spatial and temporal neuronal function for making it possible to investigate complex neural circuitry. In general, it is hard to measure evoked response while strong light stimulation directly applying on the device due to light artifact, and nontransparent metallic wires.
In this work, we developed world first transparent organic amplifier and measured evoked electrocorticography (ECoG) signals from rat which has light sensitive neuron by using 3-μm-thick flexible transparent organic electro-chemical transistors (OECTs) with small light artifact. The trans-conductance (gm) of OECTs showed 1.1 mS with 70 μm/20 μm channel dimension. The transparent OECTs was fabricated on 1.2-μm-thick parylene (diX-SR) substrate. The 70-nm-thick Au grid for source/drain of OECTs deposited on the substrate, while it showing 60% transparency. The mechanical stability of Au grid was tested by applying compression. The sheet resistance of Au grid film changed 3 Ω/sq to 7 Ω/sq after 50% compression, while sheet resistance of ITO (70 nm) changed 80 Ω/sq to 400 Ω/sq at same condition. The SU-8 for passivation layer was patterned. The PEDOT:PSS for active material of OECTs was patterned by etching process [1].
The applicability of transparent OECTs was demonstrated by measuring light evoked signal on optogenetic rat [2]. The cortical surface was stimulated by laser at a wavelength of 473 nm through the transparent and non-transparent OECT. The transparent OECT could record evoked ECoG (ΔIds/gm = 700 µV) which has double amplitude of bio response from non-transparent OECT (ΔIds/gm = 350 µV) at the same light intensity (40 mW). Finally, non-light artifact was confirmed by control experiment using non optogenetic rat. The light artifact was less than peak to peak noise level (100 nA). The non-light artifact can be obtained because of wide bandgap and high capacitance of PEDOT:PSS. We concluded that measuring evoked ECoG on optogenetic rat showed that possibility of transparent OECTs for investigation on more complicate neural circuit.
[1] M Braendlein et al, Advanced Materials 29, 13 (2017).
[2] E Boyden, et al Nature Neuroscience 8, 1263 (2005).
2:15 PM - BM09.04.03/BM07.05.03/BM08.04.03
Biodegradable and Biocompatible Force Sensor Based on a New Piezoelectric Polymer to Monitor Important Bio-Physiological Pressures
Thanh Nguyen 1
1 , University of Connecticut, Storrs, Connecticut, United States
Show AbstractMeasuring vital bio-physiological pressures such as trans-pulmonary pressure, intra-articular pressure, intra-abdominal pressure, intra-ocular pressure, intra-cranial pressure etc. is important for monitoring health status, preventing dangerous internal force build up in impaired organs, and enabling novel approaches of using mechanical stimulation for tissue regeneration. Pressure sensors are often required to be implanted and directly integrated with native soft tissues and organs, therefore they should be flexible and at the same time, biodegradable to avoid any invasive removal surgery, which could damage the interfaced tissues. There has been recent achievements of biodegradable force sensors which are based on either Silicon piezo-resistive probe or capacitive biopolymer. Although exhibiting excellent sensing performance, these devices rely on (1) passive materials which need to be electrically powered, (2) exotic electronic materials (e.g. Silicon), which have not been confirmed to be completely degradable and safe for use inside human body, and (3) complex clean room micro-fabrication processes. Recently, triboelectric sensors fabricated with biodegradable polymers have been reported. Yet, friction-induced triboelectric charges, while ideal for energy harvesting, are often susceptible to variation of force-response due to the delay of charge dissipation in the sensor. Here, for the first time, we present the study and processing of a novel piezoelectric biopolymer of poly-l-lactid acid (PLLA) and create a biodegradable PLLA force-sensor which only relies on medical materials, used commonly in FDA-approved implants, to monitor tiny biological forces. The sensor is able to sensitively detect a wide range of pressure from 1 – 18 kPa, relevant to many biological pressures such as intracranial pressure (0 – 2.7 kPa), intraocular pressure (0 - 5.3 kPa), and intrabladder pressure (0 - 3.92 kPa). With 150 µm thick poly-lactide (PLA) encapsulators, we show the sensor can sustain its performance inside a buffer solution for 2-3 days. As a proof of concept, we implanted this sensor into a mouse thorax to measure trans-pulmonary/trans-diaphragmatic pressure of the animal for detection of respiratory disorder from obstructive pulmonary diseases. This novel biodegradable force-sensor, based solely on common medical biomaterials, offers an extremely useful tool to monitor important biological pressures. The sensor could be also integrated with native/engineered tissues and organs, forming a bionic self-sensing systems which could enable many applications in regenerative medicine, drug delivery, and medical devices.
3:00 PM - BM09.04.04/BM07.05.04/BM08.04.04
Organic Bioelectronic Materials and New Opportunities for Neural Interfacing
Jonathan Rivnay 1
1 , Northwestern University, Evanston, Illinois, United States
Show AbstractDirect measurement and stimulation of electrophysiological activity is a staple of neural interfacing for mapping of circuits, diagnosis and/or therapy. Such bi-directional interfacing can be enhanced by the low impedance imparted by organic electronic materials that show mixed conduction properties (both electronic and ionic transport). Many high performance bioelectronic devices are based on conducting polymers such as poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS. However, new structure-property and device based design rules have led to a new class of formulations/materials. The incorporation of glycol side chains into carefully selected backbone motifs, for example, has enabled a new class of high performance bioelectronic materials that feature high volumetric capacitance, transconductance >10mS (device dimensions ca. 5μm), and steep subthreshold switching characteristics. We explore the implications of these new materials for neural interfacing, including the effect of device operation regimes, and their effect on recording sensitivity and power consumption.
3:15 PM - BM09.04.05/BM07.05.05/BM08.04.05
New Approach for High Performance PDMS Based Electrodes for Neuronal Recording and Stimulation
Aline Renz 1 , Klas Tybrandt 1 2 , Flurin Stauffer 1 , Greta Thompson-Steckel 1 , Janos Voros 1
1 , ETH Zürich, Zürich Switzerland, 2 , University Linköping, Linköping Sweden
Show AbstractNew approaches for the fabrication of stretchable electronic implants in healthcare applications have attracted increased attention in the past years. Enhancement of the implant-tissue interface to both reduce the foreign body response as well as achieve improved electrode properties has been the main focus of many new devices. Stretchable implants have shown promise in their ability to reduce the foreign body response, however, there are still many limitations to the successful implementation of these devices. Specifically, achieving the combination of reliable electrical recording, as well as stimulation have yet to be established to gain long-term stable implants.
Here we present a new microelectrode array fabrication method, in which electrodes with controllable diameters ranging from 30 µm to 1 mm and tunable height can be generated on PDMS. These porous nanomaterial-based electrodes exhibit stable stimulation characteristics for several thousand pulsing repetitions, and demonstrate excellent impedance values of approximately 4 kΩ at 1 kHz for a 30 µm electrode. Additionally, this method can be used for a broad range of electrode designs. Overall, these electrodes can be utilized for the recording and stimulation of electrically excitable cells and tissues for both in vitro as well as in vivo applications.
3:30 PM - BM09.04.06/BM07.05.06/BM08.04.06
Soft and Intrinsically Stretchable Inkjet-Printed Transistor Arrays with Sub-Volt Operation for Skin-Like Bioelectronics
Francisco Molina-Lopez 1 , Theo Gao 1 , Ulrike Kraft 1 , Yeongin Kim 1 , Yuxin Liu 1 , Zhenan Bao 1
1 , Stanford University, Stanford, California, United States
Show AbstractSoft and stretchable electronic materials are receiving increasing attention in the fields of biology and biomedicine. Part of the reason for this interest resides in their mechanical properties, which match those of human body and other living organisms, allowing intimately integration with them in a minimally invasive manner. On the other hand, printing electronics presents the possibility of additive low-cost deposition and patterning of a wide range of solution-processed functional materials at ambient conditions and over large areas. These characteristics suit the requirements for integration of stacked organic electronic materials in the fabrication of skin-like electronics. Among the different printing methods, inkjet has special interest as it is a digital fabrication method with the capability of depositing materials on-demand and without physical contact, facilitating prototyping and patterning on different surface topologies.
In this work, we present a soft and stretchable array of transistors with sub-volt operation for application in skin-like bioelectronics. The transistors are composed of stacks of intrinsically stretchable functional materials, namely networks of semiconducting carbon nanotubes (CNTs), ionic dielectric and conducting and stretchable PEDOT:PSS. Since these materials can be only processed from solution and do not withstand high temperatures, inkjet printing has been used to facilitate their integration at ambient conditions (below 60°C) on an elastomeric substrate. Each material of the system was first formulated as an inkjet-printable ink using orthogonal solvents, and subsequently deposited and patterned using a commercial lab-scale tabletop inkjet printer for electronics. Good resolution of few tens of micrometers over large-areas of several cm2 was achieved for every printed material. The double-layer capacitor effect of the utilized ionic gate dielectric permitted over 1 µm-thick irregular printed films to operate below 1 volt and without risk of gate current leakage. Sub-volt operation is paramount in bioelectronics to avoid water splitting and to emulate neuron synapsis behavior. Furthermore, Inkjet printing-patterning of the gate dielectric suppressed cross talk between neighboring transistors. High mobility and large on/off current ratio were achieved for the printed transistors by fine-tuning the CNT network density through controlling the number of printed passes. The excellent electrical properties of the fabricated transistors along with their mechanical softness and the versatility offered by the non-contact and maskless nature of inkjet printing, makes this system a promising general platform easily customizable for different applications in bioelectronics. Indeed, the potential of the fabricated transistors array to work as a soft wearable system for neuron interfacing will be tested, advancing the new generation of brain-machine interfacing devices and prosthetics with sensing capabilities.
3:45 PM - BM09.04.07/BM07.05.07/BM08.04.07
Organic Electronics for High-Resolution Electrocorticography of the Human Brain
Dion Khodagholy 2 , Jennifer Gelinas 1 , Gyorgy Buzsaki 3
2 Electrical Engineering, Columbia University, New York, New York, United States, 1 , Columbia University, New York, New York, United States, 3 Neuroscience Institute, NYU Langone Medical Center, New YorK, New York, United States
Show AbstractLocalizing neuronal patterns that generate pathological brain signals may assist with tissue resection and intervention strategies in patients with neurological diseases. Precise localization requires high spatiotemporal recording from populations of neurons while minimizing invasiveness and adverse events. We describe a large-scale, high-density, organic material–based, conformable neural interface device (“NeuroGrid”) capable of simultaneously recording local field potentials (LFPs) and action potentials from the cortical surface. We demonstrate the feasibility and safety of intraoperative recording with NeuroGrids inanesthetized and awake subjects. Highly localized and propagating physiological and pathological LFP patterns were recorded, and correlated neural firing provided evidence about their local generation. Application of NeuroGrids to brain disorders, such as epilepsy, may improve diagnostic precision and therapeutic outcomes while reducing complications associated with invasive electrodes conventionally used to acquire high-resolution and spiking data.
4:00 PM - BM09.04.08/BM07.05.08/BM08.04.08
Real Time Monitoring of 3D Cell Cultures In Vitro Using Conducting Polymer Scaffolds
Charalampos Pitsalidis 1 , Magali Ferro 1 , Donata Iandolo 1 , Isabel del Agua 1 , Sahika Inal 2 , Roisin Owens 1
1 , Ecole des Mines de Saint-Etienne, Gardanne France, 2 , King Abdullah University of Science and Technology, Saudia Arabia (KAUST), KAUST Saudi Arabia
Show AbstractThree-dimensional (3D) cell cultures are sought to improve the physiological relevance of cell-based assays and provide a better alternative to animal testing compared to the conventional cell-monolayer based cultures. We report herein an in vitro toxicology screening platform based on 3D conducting polymer scaffolds consisting of poly(3,4-ethylene dioxythiophene (PEDOT). The conducting scaffolds are used concurrently as a biocompatible host to support 3D cell cultures as well as an electrode to electrically probe cell behavior. Dynamic electrochemical impedance spectroscopy of the 3D conducting scaffolds reveal in real time the different features of the cell culture including adhesion, growth and proliferation. By tuning the composition parameters and the microstructural properties of the fabricated scaffolds we were able to provide a suitable 3D environment for the cells without affecting the electrical sensing capability of the device. The proposed platform tested with various cell types including fibroblasts and epithelial cells represents a nondestructive and label-free in-situ cell-based toxicity screening platform, paving the way towards next generation in vitro toxicology assays toward the reduction of animal tests.
4:15 PM - BM09.04.09/BM07.05.09/BM08.04.09
Elastic Microelectrodes for Bioelectronic Recording from Peripheral Nerves
Tobias Cramer 1 , Francesco Decataldo 1 , Davide Martelli 2 3 , Marta Tessarolo 1 , Mauro Murgia 4 , Beatrice Fraboni 1
1 Department of Physics and Astronomy, University of Bologna, Bologna Italy, 2 Department of Biomedical and Neuromotor Sciences-Physiology, University of Bologna, Bologna Italy, 3 Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria, Australia, 4 Istituto per lo Studio dei Materiali Nanostrutturati (CNR-ISMN), Consiglio Nazionale delle Ricerche, Bologna Italy
Show AbstractMonitoring of bioelectric signals in peripheral nerves is crucial to gain understanding of how the autonomic nerve system controls specific body functions related to disease states such as inflammatory response.1,2 In order to achieve long-term, chronic recordings, that do not interfere with nerve function or animal behaviour, a low-invasive wireless electrode technology has to be developed.
In this work, we present our efforts to achieve a wireless peripheral nerve interphase based on stretchable electrodes to record from the splanchnic and renal nerve in rats. Polydimethylsiloxane (PDMS) is used as elastic substrate and encapsulation material for electrodes and interconnects made of thermally evaporated Ti/Au. A kinked electrode shape has been introduced to facilitate the surgical procedure to position and fix the electrodes at the nerve. An electropolymerized layer of the doped organic semiconductor Pedot:Pss is deposited on the electrodes to reduce impedance and improve signal quality. The impact of strain on electronic and morphologic properties of the electrode are investigated. In in-vivo recordings, bioelectronic signals are amplified and digitized by a subdermal battery operated transmitter. We show that our electrode is able to record neural activity of peripheral nerves during chronic experiments in free moving animals.
1. D. Martelli, S. T. Yao, M. J. McKinley and R. M. Mc Allen, Reflex Control of Inflammation by Sympathetic Nerves, Not the Vagus, J Physiol 592.7, 1677-1686 (2014).
2. D. Martelli, D. G. Farmer, and S. T. Yao, The Splanchnic Anti-Inflammatory Pathway: Could It Be the Efferent Arm of the Inflammatory Reflex?, Exp Physiol 101.10, 1245-1252 (2016).
BM09.05: Poster Session I: Stretchable Bioelectronics
Session Chairs
Anastasia Elias
Ingrid Graz
Ivan Minev
Wednesday AM, November 29, 2017
Hynes, Level 1, Hall B
8:00 PM - BM09.05.01
A Multifunctional Skin-Like Sensor Based on a 3D Printed Thermo-Responsive Hydrogel
Zhouyue Lei 1 , Peiyi Wu 1
1 , Fudan University, Shanghai China
Show AbstractWith growing interests in the fields such as wearable devices, artificial intelligence and soft robotics, it is challenging and essential to prepare multifunctional sensors that can imitate both sensory capabilities and mechanical properties of human skin. Inspired by the concept of "ionic skin", biocompatiable hydrogels or ionic gels have shown their great potential as artificially intelligent skin, but their sensory capabilities are limited. For instance, sensing temperature has not yet been achieved in gel-based ionic sensors, although it is a key functionality of human skin that provides information about the surrounding natural environment.
Here, we develop an effective and general strategy to fabricate a multifunctional skin-like sensor by incorporating a printable and thermo-responsive hydrogel with grid microstructures into a capacitor circuit. In the circuit, the hydrogel has a low modulus and thus ensures mechanical compliance, and 3D printed microstructures can magnify capacitive area variations upon external stimuli such as temperature and pressure, which allow the hydrogel-based sensors to sense body temperature and human motion. This study not only presents a simple and promising strategy to transduce the volume phase transition behaviors of stimuli-responsive hydrogels into reliable electrical signals, but might also be helpful to develop biocompatible skin-like sensors based on hydrogels with a wide range of sensory capabilities for future soft robotics and human/machine interaction applications.
8:00 PM - BM09.05.02
Highly Sensitive, Transparent and Durable Pressure Sensors Based on Sea-Urchin Shaped Metal Nanoparticles
Donghwa Lee 1 , Youngu Lee 1
1 , Daegu Gyeongbuk Institute of Science and Technology, Daegu Korea (the Republic of)
Show AbstractPressure sensors have been used for control and monitoring in various electronic applications including force-touching sensors on the display, smart sensors embedded into fabric, medical sensors for health monitoring, and electronic skin. The capacitive and piezoelectric pressure sensors have shown excellent touching sensitivity by employing microstructures. However, they have several drawbacks such as complex device architecture, low optical transparency, and restricted scalability because the fabrication of sophisticated microstructures largely depends on complicated and expensive lithographic patterning process. Recently, piezoresistive pressure sensors composed of conductive nanomaterials (e.g., carbon nanotubes, graphene, nanowire, nanoparticles) and insulating elastomers have attracted considerable interest as potential alternatives to the capacitive and piezoelectric pressure sensors. However, most of the piezoresistive pressure sensors still have issues regarding low optical transparency and poor operational durability because high concentration of non-transparent conductive nanomaterials is required to obtain sufficient piezoresistive characteristics, which make them difficult for practical use. Therefore, the challenge still remains to develop a novel conductive nanomaterial for practical piezoresistive pressure sensors with excellent touching sensitivity, optical transparency, and operational durability. Here, we report a highly sensitive, transparent, and durable piezoresistive pressure sensor composed of sea-urchin shaped metal nanoparticles (SSNPs) and insulating polyurethane (PU) elastomer. It showed outstanding pressure sensing performance with high sensitivity of 2.46 kPa-1 due to the effective quantum tunnelling effect among SSNPs in the PU elastomer. It also exhibited superior optical transmittance (84.8% at 550 nm), fast response/relaxation time (30 ms), and excellent operational durability. In addition, we successfully demonstrated that the piezoresistive pressure sensors could detect minute movements of human muscles such as a finger bending and hand motion.
8:00 PM - BM09.05.03
Highly Sensitive and Direction-Selective Strain Sensor with Carbon Nanotube Asterisk Structure
Hayeong Jang 1 , Seolhee Baek 1 , Hwasung Lee 1
1 , Hanbat National University, Daejeon Korea (the Republic of)
Show AbstractStrain sensors respond to mechanical deformations by the change of electrical characteristics such as resistance or capacitance. Many requirements are needed to make high-performance strain sensors including sensitivity, stretchability, response speed, stability, fabrication cost, and simplicity. Especially, highly sensitive and direction-selective strain sensors are needed for accurately detecting the human motion or matter detecting. In this work, we demonstrate the highly flexible, stretchable, and sensitive CNT-based strain sensor which is possible to detect with a direction-selective signal, fabricated by ultrasonic-nozzle spray. This strain sensor has an asterisk-structure, inducing the selective resistance changes with external deformations. The strain-sensing characteristics of the sensors including stretch/release response under static and dynamic loads, stretchability, hysteresis performance, and bendability have been investigated. We explained that the resistance changes of the CNT-based asterisk structure by stretching originates from the increase of disconnection between CNT and topological changes of network. In particular, we could observe that this asterisk structure is very efficient to detect a direction-selective strain.
8:00 PM - BM09.05.04
High-Performance Pressure Sensors Based on Three-Dimensional Conductive Nanofiber Structures
O Young Kweon 1 , Joon Hak Oh 1
1 , POSTECH, Pohang Korea (the Republic of)
Show AbstractThe rapid progress of flexible electronic devices based on organic materials has advanced human-machine interface, such as wearable devices and wireless health monitoring systems. Particularly, lightweight, and inexpensive sensor devices play the most important role in proper operation of the wearable devices for detecting change of external stimulation. We introduce a very simple and efficient way to produce PEDOT/PVDF-copolymer nanofibers for application as piezo-resistive type pressure sensors. Pressure sensors can act as transducers which convert the changes in external force to an electrical signal or other recognizable signals. The nanofibers were used as a template material for elastic electrospun structures and EDOT was polymerized on the surface of fibers via vapor deposition polymerization technique. The fabricated sponge-like structured membranes exhibited higher sensitivity than conventional electrospun mats, including enhanced contact surface area and piezo-resistive effects, resulting in high-performance pressure sensing ability and outstanding durability. It showed reproducible performance over 1000 strain cycles with no deterioration in performance. Finally, highly sensitive large-area multi-array sensors with a low operating voltage of 1 V and a highly sensitive wearable band were fabricated. To the best of our knowledge, this is the first demonstration for the fabrication of electrospun membrane with three-dimensional randomly oriented fibrous structures that can monitor external pressure in high sensitivity.
8:00 PM - BM09.05.05
Highly Stretchable and Sensitive Strain Sensor Based on Three-Dimensional Bicontinuous Conductive Nanonetwork for Human Motion Detections
Donghwi Cho 1 , Junyong Park 1 , Jin Kim 1 , Taehoon Kim 1 , Jungmo Kim 1 , Seokwoo Jeon 1
1 , KAIST, Daejeon Korea (the Republic of)
Show AbstractThe demand for wearable strain gauges that can detect dynamic human motions is growing in the area of healthcare technology. However, the realization of efficient sensing materials for effective detection of human motions in daily life is technically challenging due to the absence of the optimally designed electrode. Here, we propose a novel concept for overcoming the intrinsic limits of conventional strain sensors based on planar electrodes by developing highly ordered and three-dimensional (3D) bicontinuous nanoporous electrodes. We create a 3D bicontinuous nanoporous electrode by constructing conductive percolation networks along the
surface of porous 3D nanostructured poly(dimethylsiloxane) with single walled carbon nanotubes. The 3D structural platform allows fabrication of a strain sensor with robust properties such as a gauge factor of up to 134 at a tensile strain of 40%, a widened detection range of up to 160%, and a cyclic property of over 1000 cycles. Collectively, this study provides new design opportunities for a highly efficient sensing system that finely captures human motions, including phonations and joint movements.
8:00 PM - BM09.05.06
Highly Stretchable Ag Electrodes Fabricated on Wavy-Patterned PDMS Substrate for Stretchable Interconnectors and Thin-Film Heaters
Hae-Jun Seok 1 , Jae-Gyeong Kim 1 , Hyeong-Jin Seo 1 , Eun-Hye Ko 1 , SangMok Lee 1 , Han-Ki Kim 1
1 , Kyung Hee University, Yongin-si Korea (the Republic of)
Show AbstractWe report on semi-transparent stretchable Ag films coated on a wavy-patterned polydimethylsiloxane (PDMS) substrate for use as stretchable electrodes for stretchable and transparent electronics. To improve the mechanical stretchability of the Ag films, we optimized the wavy-pattern of the PDMS substrate as a function of UV-ozone treatment time and pre-strain of the PDMS substrate. It was found that wavy-patterned PDMS substrate with a smooth buckling was beneficial for precisely patterned Ag interconnectors because the depth of buckling critically affected on the connectivity of stretchable Ag interconnectors. In addition, we investigated the effect of the Ag thickness on the mechanical stretchability of the Ag electrode formed on the wavy-patterned PDMS substrate. The semi-transparent Ag films formed on the wavy-patterned PDMS substrate showed better stretchability (strain 20%) than the Ag films formed on a flat PDMS substrate because the wavy pattern effectively relieved strain. In addition, the optical transmittance of the Ag electrode on the wavy-patterned PDMS substrate was tunable based on the degree of stretching for the PDMS substrate. In particular, it was found that the wavy-patterned PDMS with a smooth buckling was beneficial for a precise patterning of Ag interconnectors. Furthermore, we demonstrated the feasibility of semi-transparent Ag films on wavy-patterned PDMS as stretchable electrodes for the stretchable electronics based on bending tests, hysteresis tests, and dynamic fatigue tests.
8:00 PM - BM09.05.07
Multifunctional Microfluidic Capacitive Sensors Using Ionic Liquid Electrodes for Simultaneous Sensing of Pressure and Temperature
Byoung Joon Park 1 , Sun Geun Yoon 1 , Sung Min Lee 1 , Suk Tai Chang 1
1 Chemical Engineering and Materials Science, Chung-Ang University, Seoul Korea (the Republic of)
Show AbstractThere are many studies of demonstrating capactive sensors for various purposes such as detecting pressure, body motions, and temperature variation. However, its perfoming principle is mainly dependent on physical and geometrical changes of dielectric layers. In this study, we developed a new class of microfluidic capacitive sensors with utilizing ionic liquid serving as electrodes and CNT/PDMS composites (CPCs) as a dielectric layer. The working principle of our microfluidic sensors was investigated with geometrical changes of microfluidic channel and variations of electric double layer (EDL) capacitance. Our microfluidic capacitive sensors showed detection of localized pressure, lateral pressure movement, and even temperature variations with high sensitivity. By using multimodal capability, the microfluidic capacitive sensor was successfully performed as a keypad and applied to a bottle and human skin. This microfluidic capacitive sensors could offer great opportunity of development for future stretchable and flexible electronic devices such as wearable electronics, soft robotics, electronic skin, and human healthcare systems.
8:00 PM - BM09.05.08
Frequency-Modulation-Induced Broad Color-Tuning in Elastomer-Based Electroluminescent Devices
Seongkyu Song 1 , Hyunseok Shim 1 , Sang Kyoo Lim 1 , Soon Moon Jeong 1
1 , Daegu Gyeongbuk Institute of Science and Technology, Daegu Korea (the Republic of)
Show AbstractTo overcome the limitations of rigidity and brittleness in conventional devices, mechanical stretchability is an essential requirement of various optoelectronic devices. In addition to general approaches for a “wavy” structure, a polydimethylsiloxane (PDMS)-supported zinc sulfide (ZnS) composite structure, which is a mixture of PDMS and ZnS (PDMS+ZnS), has recently received considerable attention because of its intrinsically stretchable and electroluminescent characteristics.[1] In this work, we demonstrated widely color-tunable characteristics in PDMS-based, alternating-current-driven electroluminescent devices by patterning an emitting layer and employing an electrical frequency modulation.[2] By combining screen printing with the color-tunable aspect of ZnS:Cu-based phosphors, we could demonstrate various colored patterned images in a single device by simply controlling the electrical frequency. We could also show enhanced color tuning by mixing multi-color phosphors, which resulted in covering a broad range of CIE coordinates in color space. We believe that our method, as demonstrated here, could be a viable and common strategy to manipulate broader color expression in a wide range of future stretchable devices.
[1] S. M. Jeong, S. Song and H. Kim, Nano Energy 21, 154 (2016).
[2] S. Song, H. Shim, S. K. Lim and S. M. Jeong, Submitted.
8:00 PM - BM09.05.09
Highly Sensitive Flexible Capacitive Tactile Sensor Based on Air Dielectric Layer
Yan Wang 1 , Chuanfei Guo 1 , Jianming Zhang 1 , Ying Hong 1
1 , Southern University of Science and Technology, Shenzhen China
Show AbstractFlexible and highly sensitive tactile sensors have attracted much interest for their widely use in the fields of electronic skin, intelligent soft robotics, and friendly human-machine interaction. However, in conventional flexible tactile sensors, soft polymer as the foremost deformation substrate often undergoes a lateral expansion under compressive strains. Such a lateral deformation affects the surrounding area, causing complicated signals and adverse effect on positional accuracy, degree of linearity, and reliability of the signals, which is a big challenge for tactile sensors. By contrast, air is a suitable dielectric matter with the ultra-low elasticity modulus and zero Poisson's ratio. Herein, we assemble two flexible conducting plates with air dielectric layer into capacitive tactile sensor, which exhibits good flexibility, ultra-high sensitivity, fast responsibility, high positional accuracy and high linearity. Such tactile sensor based on air dielectric layer not only can be used as non-contact sensing system, but also has wide potential applications in fields of tactile displays, in vitro diagnostic devices, soft robotics, fatigue detection, and so forth.
8:00 PM - BM09.05.11
Transparent and Waterproof Fibers Based on Micro-Channels for Strain/Pressure Sensors, Temperature Sensors and Strain-Insensitive Conductors
Song Chen 1 , Shuqi Liu 1 , Haizhou Liu 1 , Pingping Wang 1 , Lan Liu 1
1 , South China University of Technology, Guangzhou China
Show AbstractIn recent years, stretchable and wearable electronics have attracted tremendous attentions due to their huge potentials in advanced humanoid robots, artificial electronic skins, and wearable devices. To mimic the human sensory systems, much effort was devoted to realizing multiple sensing abilities including strain, pressure, and temperature, as it allows the artificial sensors more humanoid. However, to the best of our knowledge, multi-parametric sensing platform is not enough for developing an intelligent sensory system in actual application: A stretchable conductor (e.g. stretchable interconnect, wire, and electrode) with strain-insensitive conductance is also indispensable in these systems for connecting and transporting electrons just be similar to the blood vessel in human body. Therefore, the simultaneous combination of multifunctional sensors and stretchable strain-insensitive conductors are desperately required in this field.
On the other hand, even though multifarious sensors were widely researched, most current reported devices were fabricated by integrating rigid metal, semiconductor, and carbonaceous materials into supporting elastic materials. These strategies do have numerous encouraging progresses until now, but the biggest issues are the mechanical mismatch between the fillers and the supporting materials. Typically, most rigid fillers have a high Young’s modulus of 1011−1012 Pa, which are about 6 orders of magnitude higher than them of the elastic substrate (105−107 Pa). The big difference in Young’s modulus can easily lead to the materials delamination and local fracturing when applied strain, limiting the durability and stability of the materials. As a result, low Young’s modulus conducting materials will be ideal fillers in the near future. In this case, ionic liquids (ILs), with Young’s modulus of <1 Pa, attracted many considerable attentions.
Herein, we fabricated a range of ILs-based strain sensors with different channel sizes. Through their resistance changes under stretching, the conductive mechanism and the influence of channel sizes on sensor's sensitivity was further investigated. Moreover, the straight channel based sensors show excellent responses to pressure and temperature. On the other hand, to fabricate a strain-insensitive conductor, a spring-like structure was introduced. Due to the extending of the helical micro-channel, the channel size can remain invariant accompanied with a stable conductance under stretching. Moreover, all the sensors and strain-insensitive conductors are fibrous, which are in favor of further processing, integrating and attachment. At last, the as-prepared sensor and conductor exhibit excellent durability. Typically, the straight channel based strain sensor shows high stability after 10000 stretch and release cycles under 20% and 40% strain, excellent long term stability with one month. The spring-like channel based conductor shows conductive stability after 10000 cycles under 50% strain.
8:00 PM - BM09.05.12
Fabrication of Capacitive Pressure Sensors Utilizing Surface Roughness
Gwangmook Kim 1 , Kilsoo Lee 1 , Jaehong Lee 1 , Taeyoon Lee 1 , Wooyoung Shim 1
1 , Yonsei University, Seoul Korea (the Republic of)
Show AbstractFabrication strategies that pursue “simplicity” for the production process and “functionality” for a device, in general, are mutually exclusive. One of these competing demands is usually met by compromising the other, and therefore, strategies that are less expensive, less equipment-intensive, and consequently, more accessible to researchers for the highly functional device, are required. Here, we present a conceptually different approach, which utilizes the surface roughness of paper to realize a capacitive pressure sensor with high performance compared with sensors produced by costly microfabrication processes. In this study, we utilize a writing activity with a pencil and paper, which enables the construction of a fundamental capacitor that can be used as a flexible capacitive pressure sensor with high pressure sensitivity and short response time and that it can be inexpensively fabricated over large areas. Unlike previous studies, all three parameters in the context of a capacitor (i.e., electrode area, electrode separation and dielectric constant) are simultaneously controlled by utilizing surface curl and roughness, which maximizes the sensing capabilities. Furthermore, we successfully integrated the capacitor elements into a fully functional 3D touch-pad device acting as a pressure sensor-based peripheral input device, which is a step toward the realization of advanced paper electronics that achieves a high simplicity and functionality.
8:00 PM - BM09.05.13
Nanoparticle Embedded Transparent Capacitive Pressure Sensors
Hyeohn Kim 1 , Gwangmook Kim 1 , Taehoon Kim 1 , Wooyoung Shim 1
1 , Yonsei University, Seoul Korea (the Republic of)
Show AbstractHighly sensitive capacitive pressure sensors are opening pathways for engineering the electronic skin that perceives mechanical stimuli. Recent advances reveal routes to exploit the micropatterned dielectrics so as to control the effective dielectric constant and thereby enhance the sensing performance of the devices, but generally are opaque and haze due to light scattering at the microstructured surfaces. To overcome this challenge, typically made of transparent dielectrics, such devices often utilize a flat and smooth dielectric surface. These components increase the optical transparency, but degrade the sensor performance because of the absence of air-gap. To this end, for the first time, we bring the issue of ‘mutually exclusive’ relationship between the pressure sensitivity and optical transparency in wider context of capacitive pressure sensors.
In this study, we propose a new, fundamentally simple approach to fabricating nanoparticle-dispersed pressure sensors that can provide a protocol for making a dielectric layers with transparent SiO2 nanoparticles making the surface rough, but reducing the haze at optimum particle sizes, thus providing high sensitivity and transparency. To secure the roughness and transparency, the poly-disperse nature of nanoparticle is used to activate the two different state of spontaneous nanoparticle dispersity; (i) homogeneous dispersion where each nanoparticle with a size comparable to visible light wavelength has low light scattering, and (ii) heterogeneous dispersion, where aggregated nanoparticles form micrometer-sized feature, increasing effective dielectric constant and pressure sensitivity.
Our new transparent capacitive pressure sensor has simple and versatile design architecture, and it also addresses the fundamental limitations of nanoparticle-driven devices by allowing one to use a spontaneous entropy-driven reaction between nanoparticles to fabricate the reliable device in scalable fashion. In fact, nanoparticle-dispersed dielectrics (nanometer-scale) are used to build a highly sensitive pressure sensor that mimics pressure-sensitive human skin, which is further integrated into a fully functional three-dimensional (3D) touchpad device (centimeter-scale) as a principle demonstration of the concept of post-touch solutions.
8:00 PM - BM09.05.14
All-Printing Based, Capacitive Pressure Sensors on Paper
Taehoon Kim 1 , Kilsoo Lee 1 , Gwangmook Kim 1 , Wooyoung Shim 1
1 , Yonsei University, Seoul Korea (the Republic of)
Show AbstractDeveloping low cost, high performance, and flexible pressure sensors is highly desired for versatile applications such as electronic skins, monitoring patients, and human motion detection. In particular, the capacitive pressure sensor has advantages in terms of high sensivitity, low power consumption, and simple design due to its simple governing equation. To achieve the high-performance capacitive pressure sensors, many groups have mainly focused on developing the microstructured or porous dielectric layers. However, they suffer from significant drawbacks including complex and high-cost microfabrication process. To overcome these drawbacks, simple and low-cost fabrication process are required. Here, we demonstrate the capacitive pressure sensors that are fabricated on the commercial photo paper using typical desktop inkjet and laser printer. Specifically, we present a conceptually new apprach that forms the microisland-like dielectric layer to realize the capacitive pressure sensor with high performances. In more detail, we utilized the electrostatic digital printing process of laser printer to make microisland-like dielectric layer. The fabricated pressure sensor exhibited high sensitivity, fast response and relaxation times in the millisecond range, and excellent stability. Furthermore, the sensor could be integrated into multipixel array readily by using printing method, which can potentially enable the development of various applications. To demonstrate the utilization of our pressure sensor, we have successfully developed a few of force-touch input devices, i.e., keyboard and trackpad. A printing is the simplest all-in-one method for drawing electrodes and forming dielectric layer to make capacitive pressure sensor, which can be step toward the realization of advanced paper electronics.
8:00 PM - BM09.05.15
Flexible Composites Based on Polyurethane and Graphene Oxide—Eletromechanical Characterization for Applications in Tactile Feedback
Flavio Borges 1 , João Clerici 1 , Daniel Ugarte 1 , Cecília Silva 2 , Monica Cotta 1
1 Department of Applied Physics, University of Campinas - UNICAMP , Campinas, SP, Brazil, 2 MackGraphe- Center for Advanced Research in Graphene and Nanomaterials and Nanotechnologies, Mackenzie Presbyterian University, São Paulo, SP, Brazil
Show AbstractThe technology of wearable devices advances at a fast pace, creating oportunities for new medical applications. In particular, for pressure sensing and transduction, direct contact between sensor and target object is necessary. When this object is soft, the flexibility of pressure sensors is an important parameter for suitable device performance.
In this work, we report on the synthesis of low cost composites based on poliurethane (PU) and reduced graphene oxide (r-GO) for applications in tactile feedback for neurologically impaired subjects. For the fabrication of the composites, we used two protocols of deposition (by dispersion or centrifugation) of Oxide Graphene (GO) in PU sponges with different densities. Reduced GO was obtained by immersion in acid ascorbic; the electrical resistances of the samples dropped by 1 to 2 (2 to 3) orders of magnitude for the dispersion and centrifugation protocols, respectively.
Structural characterization of the samples by scanning electron microscopy shows that both GO and r-GO adhere to the sponges; however, the PU pore structure changes as a function of PU density, influencing graphene incorporation. Electrical resistances of the samples were measured as a function of compression length and applied force. A linear relation between resistance and compression was observed; resistance varied exponentially with applied force, at the ranges expected for object manipulation. In order to analyze the dependence of electrical characteristics of the composite material on the contact area during deformation as well as the process reproducibility, a specific setup based on a home-made micromanipulator was designed. We thus expect to have a more controlled and precise characterization of the elastic properties of the PU-rGO composite.
8:00 PM - BM09.05.16
A Flexible Dual-Mode Tactile Sensor Derived from Three-Dimensional Porous Carbon Architecture
Zifeng Wang 1
1 , City University of Hong Kong, Kowloon Tong Hong Kong
Show AbstractDetecting and monitoring varieties of human activities is one of the most essential functions and design purposes of different kinds of wearable sensors. Apart from excellent sensitivity and durability, limited by the materials, most of the sensors reported in the literatures are only capable of detecting signals based on sole mechanism. In this work, a dual-mode flexible sensor derived from high temperature pyrolysized 3D carbon sponge (C-Sponge) was proposed as peculiar sensor materials that are able to detect human activities based on fundamentally different mechanisms, either by triboelectric effect or by piezoresistive effect. The sensor generated average open circuit voltage up to ～2 V and short circuit current up to ～70 nA when being used as self-powered triboelectric sensor, which was sufficiently sensitive for detecting finger touching and plantar pressure distribution of human feet. On the other hand, by incorporating MWCNT into the 3D structure, the sensor at piezoresistive mode exhibited a sensitivity improvement of nearly 20-fold, from less than 40% to more than 800%, and a durability improvement of more than 22-fold (240,000 cycles) compared with those of original C-Sponge fabricated at 1000 oC (10,800 cycles). All the experimental results indicated that the proposed flexible dual-mode sensor is potentially applicable as wearable sensors for human activity monitoring.
8:00 PM - BM09.05.17
Flexible Acceleration Sensors Based on Piezoionic Effect
Takahiro Kondo 1 , Masaki Sato 1 , Hidenori Okuzaki 1
1 , University of Yamanashi, Kofu Japan
Show AbstractIn this study, fabrication and characterization of flexible acceleration sensors driven by piezoionic effect have been demonstrated. The ionic liquid-polyurethane (IL-PU) gels were prepared by casting the N,N-dimethylacetoamide (DMAC) solution of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMI][TFSI]) and thermoplastic polyurethane. Then, poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT:PSS) containing polyglycerin (PG) as stretchable electrodes were spray-deposited on both sides of the IL-PU gel. The sensor characteristics of the PEDOT:PSS-PG/IL-PU gel films were evaluated with a charge amplifier under bending using a mechanical tester.
Upon bending the gel, positive electric charges are rapidly generated, whereas the equivalent negative charges are formed when the bending stops. On the other hand, the opposite phenomenon was observed when the bent gel recovers to the original straight shape, indicative of an acceleration sensor. Indeed, the electric charge increases in proportion to the acceleration, where the sensitivity was 5.3 nC/(m/s2). The value is three orders of magnitude higher than that of the commercial piezoelectric sensors. The mechanism can be explained in terms of the “piezoionic effect” based on the difference of ionic mobilities between the EMI+ and TFSI-. For example, upon bending the sensor, the EMI+ with higher mobility move toward anode due to the surface expansion, generating the positive electric charges. Then the electric charges decreased because the TFSI- follow afterwards. On the other hand, when the bending stops, polarization relaxation may cause negative electric charges in the same manner. Therefore, the piezoionic effect should be affected by molecular structure of the IL. Indeed, various ILs with different alkyl chain lengths of imidazolium cations such as [EMI][TFSI], 1-buthyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMI][TFSI]), 1-hexyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide ([HMI][TFSI]), and 1-methyl-3-octhylimidazolium bis(trifluoromethylsulfonyl)imide ([MOI][TFSI]) were investigated. It was found that the longer the alkyl chains of the imidazolium cations, the lower the both ionic conductivity and transference number of cations. Therefore, the electric charges generated by the bending increased in the order of [MOI][TFSI], [HMI][TFSI], [BMI][TFSI], and [EMI][TFSI] which is the same order of the ionic conductivity and transference number of cations. On the basis of this phenomenon, we have succeeded in fabricating a wearable sensor glove, in which the flexible acceleration sensors located on the three fingers are operating individually. Since the acceleration sensor can provide information not only the acceleration but also force, velocity, and displacement, the wet-processbable, stretchable, and wearable flexible sensors based on the piezoionic effect will be available for motion sensors in a wide field of application.
8:00 PM - BM09.05.18
Flexible Printed Pressure Sensors with Organic TFTs for Healthcare Applications
Tomohito Sekine 1 , Ryo Sugano 1 , Tashiro Tomoya 1 , Jyun Sato 1 , Daisuke Kumaki 1 , Fabrice Domingues Dos Santos 2 , Atsushi Miyabo 3 , Shizuo Tokito 1
1 , Yamagata University, Yonezawa Japan, 2 , Piezotech, Pierre-Benite France, 3 , ARKEMA K. K., Kyoto Japan
Show AbstractFlexible printed pressure sensors possess great potential advantages for wearable and disposable healthcare applications such as a thermometer. Recently, we reported a flexible printed pressure sensor that was fabricated using a ferroelectric polymer, Poly (vinylidenefluoride-trifluoroethylene) [P(VDF-TrFE)], by printing methods [1]. Here, we demonstrate a newly developed flexible printed pressure sensor consisting of the ferroelectric polymer layer and an organic thin-film transistor (OTFT) on a plastic film substrate in order to monitor the human pulse rate.
The P(VDF-TrFE) layer was formed as a pressure detector and the printed OTFT was fabricated as a voltage amplifier for the pressure detector by inkjet printing and spin-coating methods. The printed OTFT and the P(VDF-TrFE) layer were fabricated on a same film substrate. This P(VDF-TrFE) layer could generate the voltage of 10 mV by applied pressure of 15 N mm-2. The characteristics of the OTFT was measured at VDS = −10 V, VGS = +10 to −10 V. The estimated field-effect mobility μeff in the saturation region for the OTFT was 0.5 cm2 V-1 s-1 and the threshold voltage was −0.17 V [2]. We estimated the ability of the printed OTFT as the amplifier by using a simulation-program-software (LT-Spice), and found an amplification factor of 1.7. The relationship between applied pressure and output voltage in our sensor was measured. The pressure was applied to the P(VDF-TrFE) layer by using a pressure tester. The output voltage of the pressure sensor linearly displayed a clear correlation with the applied pressure and the output voltage was 17 mV in the pressure of 15 N mm-2, which is almost consistent with the simulated value. This results indicate that the output voltage generated in the P(VDF-TrFE) layer was obviously amplified by the printed OTFT. Further improvement in the pressure sensitivity would be expected by using multiple the OTFTs.
Finally, we demonstrated the monitoring of the human pulse rate using the printed pressure sensor. In the printed sensor operation, VDS and VGS of the OTFT were fixed at −3 V. That sensor was attached to the skin near the neck of a volunteer using a skin-compatible adhesive patch. The sensor clearly detected the human pulse rate and the monitored rate was 55 pulse per minute. This study demonstrates that the employment of printed OTFTs for the pressure sensor is effective for improving the sensitivity in healthcare monitoring.
The detection of the pulse rate from human is authorized by the Ethics Committee of Yamagata University (authorization code: 29-2).
[1] T. Sekine et al., Japanese Journal of Applied Physics, 55, 10TA18 (2016).
[2] R. Shiwaku et al., Scientific Reports, 6, 34723 (2016).
8:00 PM - BM09.05.19
Infrared Actuation-Induced Simultaneous Reconfiguration of Surface Color and Morphology for Smart Artificial Skins
Seyedali Banisadr 1 , Jian Chen 1
1 Department of Chemistry & Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, United States
Show AbstractCephalopods, such as cuttlefish, exhibit remarkable capability to adopt the coloration and texture of their surroundings through adjusting their skin color and surface morphology simultaneously, for the purpose of camouflage and communication. Inspired by this unique feature of the cuttlefish skins, we present a general approach to remote-controlled, smart artificial skins that undergo simultaneous changes of surface color and morphology upon infrared (IR) actuation. The smart artificial skin is based on a reconfigurable laminated structure that comprises an IR-responsive shape-changing nanocomposite film as an actuator layer which is directly integrated with a mechanochromic elastomeric photonic crystal layer. The laminated film can be readily disassembled and reassembled in order to be repurposed for various needs. Upon global or localized IR irradiation, the actuator layer demonstrates fast, large, and reversible strain in the irradiated area, which causes a coupled change in the shape of the laminated film and colorimetric signal of the mechanchromic elastomeric photonic crystal film in the same area. Various complex 3D shapes, such as bending and twisting deformations, can be generated under IR irradiation, through modulating the strain direction of the actuator layer of the laminated film. Furthermore, the current laminated system has been used in a remote-controlled soft robotic device, an inchworm walker, in which a color-changing skin is directly coupled with robotic movements. Finally, the feasibility of audio communication as a complimentary communication mode for human-robot interactions has been demonstrated by converting image signals of the laminated film in motion into corresponding distinct audio signals. Such bio-inspired, smart artificial skins open up promising routes for soft robotics and wearable devices.
8:00 PM - BM09.05.20
Electrochemically Powered Carbon Nanotube Artificial Muscles
Jae Ah Lee 1 , Na Li 2 , Carter Haines 2 , Raquel Ovalle 1 , Ray Baughman 2
1 , Nano Science and Technology Center, Richardson, Texas, United States, 2 UTdallas, Nanotech Institute, Richardson, Texas, United States
Show AbstractDespite major advances in past decades, the performance of humanoid and biomimetic robots have been limited by the high weight and the bulky, unnatural shape of conventionally deployed motors and hydraulic systems. Material-based artificial muscle fibers have been sought to meet the demands of the next generation of advanced robotics, such as the ability to lift giant weights and provide dexterous manipulation, but such technologies have yet to realize the desired combination of large strokes, high gravimetric work capacities, short cycle times, and high efficiencies.
We have here developed lightweight muscle fibers that can match the large stroke of natural human muscle fibers, far exceed the work capabilities of the same size natural muscle, and provide higher efficiency than other electrochemically or thermally driven yarn muscles. We demonstrated electrochemically powered carbon nanotube yarn muscles that provide tensile contraction as high as 16.5%, which is 12.7 times higher than previously obtained. These electrochemical muscles can deliver a contractile energy conversion efficiency of 5.4%, which is 4.1 times higher than reported for any organic-material-based muscle. All-solid-state parallel muscles and braided muscles, which do not require a liquid electrolyte, provide tensile contractions of 11.6% and 5%, respectively. These muscles might eventually be deployed for a host of applications, from robotics to perhaps even implantable medical devices.
8:00 PM - BM09.05.21
Stiffness Tunable Composites Structured with Soft Materials for Wearable Soft Robotics
Seunghee Jeong 1 2 , Dario Floreano 1
1 Engineering, EPFL, Lausanne Switzerland, 2 Engineering Sciences, Uppsala University, Uppsala Sweden
Show AbstractWearable soft robotics requires understanding on human motions and perceptions that can be effectively interactive with machines, and it requires consideration of not only human aspects, but also physical functions of wearable systems, which are consisted of many components. In order to provide a smart guidance of gestures with wearable systems, which can prevent significant miscontrols or help much more precious controls of machines through wearable systems, the concept of heterogeneous stiffness structures in wearables can initiate a new design approach.
Here, stiffness tunable composites (STCs) made with soft materials, such as liquids and polymers, provide a new design solution to wearable systems. Heterogeneously STC-patterned structures differentially become either compliant or stiff at dedicated contacts on human body, and they can change stiffness under a thermal stimulus depending on an encountered situation. Various liquids and polymers of phase change at low temperature are patterned and structured in elastomers to realise heterogeneous stiffness structures, which are fabricated by printing-based processes. Stiffness contrasts in stiffness tunable structures are controlled by heating and cooling systems. Previously developed, highly thermal conductive elastomer composites enhance tuning speed of stiffness contrasts. Discretised STC structures in wearable systems perform to set stiffness contrasts at the interface between human body and wearable systems, which efficiently guide human motions by mechanically allowing or restricting certain degrees of freedom of body motions in order to accomplish assigned tasks interacting with machines.
8:00 PM - BM09.05.22
3D Printing a Highly Stretchable Silicone—Coupling Curing Kinetics, Rheology and Line Shape to Bound Printable Regions of In-Line Mixed Materials
Stephanie Walker 1 , Uranbileg Daalkhaijav 1 , Osman Yirmibesoglu 1 , Dylan Thrush 1 , Yigit Menguc 1
1 , Oregon State University, Corvallis, Oregon, United States
Show AbstractIn this work, a highly stretchable soft silicone thermoset is mixed in-line and 3D printed into small enclosed soft robot actuator shapes. By using an in-line mixing system, several reactive chemistries can potentially be printed out of difficult soft materials. In order to make smaller, higher resolution soft devices using a variety of chemistries, reaction kinetics and rheology have to be incorporated into the printing plan. While controls like flow rate, nozzle diameter, print speed, pump strength, and printing environment are important considerations when printing soft materials, they are arbitrary based on the material system used. More importantly, how the printed fluid performs while being extruded, as well as the transient curing behavior, limits the kinds of structures and sizes that can be printed. To characterize the transient behavior of these kinds of curing fluids, curing kinetics, rheology, and printed line shape are coupled in this work to bound a printable region using the metrics of cure percent, elastic modulus (G’), spanning distance, and printed shape deformation over time at various temperatures. Differential scanning calorimetry (DSC) isothermal tests are performed to elucidate curing kinetics and propose a model for cure percent based on time and temperature. Dynamic oscillatory shear rheological experiments are performed to gather data about the elastic modulus and yield stress of the printable fluid versus time and temperature. Profilometry is performed on printed lines of the silicone to determine the extent to which the printed fluid deforms vertically after extrusion at various temperatures, and an optimal operating temperature range is determined. Optical microscopy is used to quantify the maximum spanning distance of an extruded silicone filament. Cure percent over time, G’ over time, yield stress, vertical deformation after printing, and spanning during printing are then correlated into a general set of parameters for bounding the 3D printable regions of the silicone. Using these optimized parameters, several enclosed pneumatic actuator structures with varying internal geometries for potential use in robot grasping and manipulation are printed as a demonstration of the effectiveness of these methods in defining printability, with the hope that these parameters and methods can be applied to similar systems to expand the 3D printing materials space.
8:00 PM - BM09.05.23
Highly Conductive and Electrochemically Stable Transparent and Stretchable Coaxial Bimetallic Ag–Based Nanowire Network and Its Application in Asymmetric Supercapacitors Energy Storage
Sangbaek Park 1 , Alvin Wei Ming Tan 1 , Jiangxin Wang 1 , Pooi See Lee 1
1 , Nanyang Technological University, Singapore Singapore
Show AbstractA critical need in deformable/stretchable electronics, flexible transparent displays/screens and their integration into human-body is to find suitable energy storage units that offer similar physical or optical properties as soft electronics while meeting the energy or power requirements. Ag nanowire networks embedded in an elastomeric polymer matrix is one of the most competitive stretchable transparent conductors with several advantages, e.g. good mechanical robustness, high conductivity and optical transparency, as well as compatibility with the conventional manufacturing process by avoiding the use of pre-strained substrates. Despite such good characteristics, the use of Ag nanowire for energy storage devices has been limited due to its poor electrochemical stability, which is one of the fundamental challenge. In this study, we suggest the preparation of coaxial Ag–bimetallic nanowire networks where the conductive and stretchable Ag nanowire networks were thoroughly covered with a secondary metallic nanoshell layer that could be electrochemically stable in alkaline aqueous electrolyte over broad potential range. As a proof of concept, Ag–Ni and Ag–Fe core–shell nanowire networks embedded in polyurethane acrylate polymer substrates were fabricated as stretchable transparent electrodes for asymmetric supercapacitors through a facile electrodeposition and transfer method. The Ag–bimetallic nanowire electrodes exhibited 50% transparency at 550 nm and stable conductivity with the tensile strain up to 100%. The unique structure where the welded Ag nanowire network is thoroughly covered with Ni or Fe nanoshells guarantees a high electrochemical stability even after 1000 cycles in the cyclic voltammetry test in 1 M KOH electrolyte over the potential range from –0.1 to 0.7 V vs. Ag/AgCl, as well as providing high specific capacitances (~ 3 mF cm−2) due to the surface Faradaic reactions of metal oxide/hydroxide layers. The asymmetric device assembled with a PVA/KOH electrolyte delivered high energy density (0.68 mW h cm−3) and power density (313 mW cm−3) with a large operating voltage of 1.6 V, and retained 92% capacitance of its original value over 5000 cycles even after stretching to 35% strain. Furthermore, a transparent and stretchable asymmetric supercapacitor is demonstrated for the first time by combining the micro-patterned Ag–bimetallic nanowire electrodes. This work offers a feasible way for electrochemically durable metal nanowire transparent conductors, which is versatile for next-generation electrochemical devices in integrated wearable electronic systems.
8:00 PM - BM09.05.24
Bioinspired Superstretchable Triboelectric Nanogenerator as Energy-Harvesting Skin for Self-Powered Electronics
Fang Yi 1 , Xiaofeng Wang 2 , Yajiang Yin 2
1 , Peking University, Beijing China, 2 , Tsinghua University, Beijing China
Show AbstractIn this work, a bioinspired stretchable triboelectric nanogenerator (TENG) was developed as energy-harvesting skin to generate electricity from human motion for energy supply of personal electronics. Inspired by biological cells, the TENG has patterned interconnected cellular structures, with physiological saline as the electrode and silicone rubber as the encapsulation and triboelectric layer. The cell-like honeycomb periodic configurations endow the TENG with improved mechanical strength, indentation resistance, shock resistance and fracture toughness. The TENG can endure a strain of as large as 600% and has a transmittance of as high as 62.5%. The TENG can effectively harvest energy from vertical and lateral motion, with a maximum instantaneous power density (2.3 Hz) and direct current power density of ~11.6 W/m2 and ~2.65 mW/m2 respectively. The performance of the TENG maintained under various strain. With sorely the energy harvested from hand motion, the TENG combined in a self-charging power unit with a power management circuit can continuously power an electronic watch, demonstrating this energy-harvesting skin’s ability to serve as sustainable energy supply for personal electronics. Moreover, a TENG and a micro supercapacitor are combined by sharing the same solution as not only the electrode of the TENG but also the electrolyte of the supercapacitor, which simplifies the architecture and fabrication process of self-charging power systems. This work provides a new prospect for skin-mounted energy harvesters as power sources and offers new options for wearable and portable electronics to achieve a sustainable operation.
8:00 PM - BM09.05.25
Stretchable Platform Enabled with Wireless Power for Smart Contact Lenses
Andres Vasquez Quintero 1 , Rik Verplancke 1 , Herbert De Smet 1 , Jan Vanfleteren 1
1 , imec, University of Ghent, Zwijnaarde Belgium
Show AbstractA smart contact lens, envisioned to correct or improve the vision, entails the integration of electronics components such as: Si chips, power source, electro-optic module and Radio Frequency (RF) antenna. The latter is thought to be the main interface for wireless communication and energy transfer at the High Frequency (HF) range. These components are interconnected by non-conventional electrical layouts in a fully stretchable platform which fulfill the essential requirements for eye wearable devices (conformal fitting and optical transparency, etc.). The fabrication process presented here relies on the thermoforming of a flat platform (electronics layout, chips and RF antenna) into a curvilinear spherical geometry fitting the eye’s shape (curvature radius: 9 mm). In particular, we introduce the platform’s mechanical carrier as a soft and biocompatible thermoplastic polyurethane (TPU), which serves as the thermoforming element and provides the essential support and stretchability. A developed thermoforming 3D and time domain Finite Element Model (FEM) using COMSOL is used for the prediction of the final lens curvature and the analysis of the induced mechanical stress throughout the thermoforming steps. The electronic platform includes a thinned-down (25 μm) Near-Field Communication (NFC) chip (M24RL64E from ST) which incorporates an RF energy harvesting module providing a direct current output when coupled magnetically. The NFC chip is interfaced with an ultra-compact RF loop antenna. The antenna was designed and optimized with a combination of analytical equations and subsequent RF momentum simulations with the software Advanced Design Systems. This optimization and a modified pattern plating process resulted in a width, gap, loops and thickness of the antenna of: 24 μm, 6 μm 13 and 10 μm, respectively, which in turn provided a quality factor around 10. Two port S parameters, reading distances, power transfer and frequency matching were validated by comparing fabricated prototypes and RF momentum models, enabling HF energy transfer for smart contact lenses and even other wearable devices in close contact with the body. A measured inductance of 4.78 μH combined with the NFC chip input capacitive impedance (27 pF) were able to communicate with an NFC-ready smartphone and custom reader at 13.56 MHz in order to give external power to an on-lens micro solid-state light emitting diode. The mechanical FEM model served to optimized meandered designs on the TPU-based platform in order to accommodate mechanical deformation during thermoforming, which in turn allowed for an optimal wrinkle-free RF antenna design and platform design. Parallel processing in combination with a short thermoforming step at relatively low temperature, paves the way towards mass scalable fabrication of soft smart contact lenses with integrated electronic components, including Si chips, electro-optics, RFID antennas, micro-size batteries and photovoltaic cells, among others.
Symposium Organizers
Ingrid Graz, Johannes Kepler University Linz
Anastasia Elias, University of Alberta
Ivan Minev, Technische Universität Dresden
Benjamin O'Brien, StretchSense
BM09.06: Materials II
Session Chairs
Anastasia Elias
Ingrid Graz
Ivan Minev
Sigurd Wagner
Wednesday AM, November 29, 2017
Sheraton, 2nd Floor, Republic B
8:30 AM - *BM09.06.01
The Ideal Robot Skin—A Robot in Itself or a Designed Material?
Liyun Yu 1 , Piotr Mazurek 1 , Anne Ladegaard Skov 1
1 Department of Chemical Engineering, Danish Polymer Centre, Kgs Lyngby Denmark
Show AbstractSilicone elastomers in various shapes are heavily used as electronic skin and for robotics. They possess inherent softness but the complexity of natural skin is nevertheless not reproduced. For example, touch and feel of silicone elastomers are far from that of human skin. In this presentation focus is on how silicone elastomers – in simple ways – can be formulated to possess different characteristics with focus on traditional mechanical and electrical properties but also with respect to commonly less characterized properties required for mimicking human skin such as liquid handling properties (water permeation and water uptake).
Different formulation strategies are applied and discussed such as bimodal elastomers, liquid-filled elastomers and foamed structures. Bimodal elastomers result in soft and stretchable materials resembling the structural heterogeneity of skin. Liquid-filled elastomers can in the same manner be tuned to possess heterogeneity but with additional properties from the incorporated liquid, such as moisture uptake causing wrinkling or with significantly increased water permeation. Foams possess yet other possibilities due to their inherent lightness and flexibility. All strategies lead to different possibilities, also beyond robotic skin, such as electronic skin, sensors and actuators. The developed materials will therefore also be discussed in the context of being used as actuators.
9:00 AM - BM09.06.02
Electrospun Nanofiber Electrodes—Conductive, Flexible and Stretchable
Han-Hsuan Chen 1 , Jyun-You Su 1 , Chien-Tin Lin 1 , Yu-Yu Cho 1 , Changshu Kuo 1
1 Department of Materials Science and Engineering, National Cheng Kung University, Tainan Taiwan
Show AbstractOrganic and inorganic nanofiber-based electrodes were fabricated via the polymer-assisted electrospinning techniques. Materials, including conducting polymers, metal oxides, and core-sheath composites, were adopted to construct the optical transparent, flexible, stretchable or even gas-permeable nanofiber electrodes. Electrospinning solutions containing polymers and certain precursors were first formulated, followed by their electrospinning under the high applied voltage to generate nanofibers with controllable fiber diameters. As-spun nanofibers were subjected to calcination, chemical reaction, or plasma surface bombardment that triggered the formation of the conductive domains in outer sheaths or in entire fibers. The sheet resistances of these electrodes were mainly dependent on the nature of the conductive domain itself, the amount of nanofiber depositions, and the nanofiber joints. Mechanical performances of these conductive nanofibers, on the other hand, were determined by their compositions, orientation, diameters, deposition amounts, joints, and underneath substrates. In this presentation, various electrospun nanofiber electrodes were prepared and investigated with respects to the different topics. For instances, electrospun zinc oxide nanofibers depicted the relationship between their conductivity and optical transparence. And, polyester/polyaniline core-sheath nanofibers were synthesized to expose the conductivity profile versus the material distortions. Finally, the plasma-synthesized polyester/silver core-sheath nanofibers revealed the most promising flexible and stretchable fiber-based electrodes for the uses of wearable devices. With robust polyester inner cores, these electrospun nanofiber electrodes also demonstrated the substrate-free and gas-permeable applications.
9:15 AM - BM09.06.03
cYarnsTM—Its Properties and Possibilities
Takahiro Ueda 1 , Julia Bykova 1 , Md Hasmat Ullah 1 , Marcio Lima 1
1 , LINTEC OF AMERICA, INC., Richardson, Texas, United States
Show AbstractA novel method to manufacture composite carbon nanotubes yarns (cYarns™) by spinning vertically aligned nanotube forests allows the large scale manufacturing of multifunctional yarns that can be introduced into textiles using conventional techniques. Addition of guest materials during the spinning process produces unique yarns with the guest material content as high as 99%wt. Such hybrid yarns can be used as electrodes for batteries, supercapacitors and fuel cells, catalytic membranes, magnets, highly porous absorbers, and strong structures containing biomedical agents. When spun with elastomers and submitted to a special twisting process, cYarns™ can be also used as actuators capable to respond either to electrical or chemical stimuli. Besides of excellent tensile strength to weight ratio, this conductive yarns show exceptional fatigue and chemical resistance making it an attractive material for wearable electronics.
9:30 AM - BM09.06.04
Nanofibrous Skin-Mountable Flexible Strain Sensor for Large-Strain Human Motion Detection
Nazanin Khalili 1 , Hassan Asif 1 , Hani Naguib 1 2 3
1 Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada, 2 Materials Science Engineering, University of Toronto, Toronto, Ontario, Canada, 3 Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
Show AbstractElectrospun polymeric fibers have the potential to be utilized as strain sensors due to their large surface to weight/volume ratio, high porosity and pore interconnectivity. Electrospinning technique is a facile and versatile method to produce fibers with tunable diameters ranging from nanometer to micrometer. Using this technique, the morphology, functionality, and fibrous architecture of the film can be tailored. Large strain flexible strain sensors are used in numerous applications including rehabilitation, health monitoring, sports performance monitoring and more specifically in physiology and kinesiology applications where large strain detection should be accommodated by the sensor. This has boosted the demand for a skin mountable stretchable, flexible and highly sensitive sensor able to detect a wide range of mechanically induced deformations. Herein, a physically cross linked polylactic acid (PLA) and thermoplastic polyurethane (TPU) blend is made into microfibrous networks via electrospinning technique. The PLA/TPU weight ratio is optimized to obtain a targeted attainable strain of 100% while maintaining its mechanical integrity. Using vaper phase polymerization, a homogeneous layer of polypyrrole (PPy) is deposited onto the as-spun fiber mat to induce electrical conductivity to the surface of the fibers. Moreover, utilizing the shape memory effect of the PLA/TPU fiber mats, the sensor is able to regain its full mechanical and electrical conductivity after large strains. It is shown that the sensor is responsive to both tensile and bending stresses with a maximum gauge factor of 30 and 10, respectively. The sensor also exhibited a consistent response under cyclic loading with different strain rates.
9:45 AM - BM09.06.05
Kirigami Enhancing Film Adhesion—Mechanism and Applications to Kirigami Wearables
Ruike Zhao 1 , Shaoting Lin 1 , Hyunwoo Yuk 1 , Xuanhe Zhao 1
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractStructures of films bonded on substrates are used in diverse technological applications such as flexible electronics, soft robots, bio-inspired adhesives, thermal-barrier coating, medical bandage and living devices. While maintaining adhesion of films on substrates is critical in these applications, the films are usually prone to delamination failure when the substrates are highly deformed. In many cases, it is challenging to vary the thickness or rigidity of the films or tune the interfacial toughness; and new methods to enhance film adhesion are of critical importance in various fields. Here we show that rationally designed kirigami cuts in a film on substrate can greatly enhance the critical strain for overall detachment of the film, especially on substrate undergoing inhomogeneous deformation. We find that the effective enhancement of adhesion by kirigami is due to i) shear lag effect of the film segments; ii) partial debonding at the film segments’ edges; and iii) compatibility with inhomogeneous deformation of the substrates. This new mechanism of kirigami enhancing adhesion has been validated by numerical simulation and experiments. We further demonstrate novel applications including kirigami bandage, kirigami heat pad, and 3D-printed kirigami wearable electronics that achieve much enhanced adhesion on skin without changing thickness or rigidity of films or film-substrate interfaces. In particular, we find that the kirigami film can better accommodate the deformation of wavy conductive wires adhered on or embedded in the films without delamination than continuous films. While kirigami has been intensively studied for programming film materials with desirable shapes and mechanical properties, fabricating stretchable electronics with enhanced strechability, and designing assembly of 3D structures; to our knowledge, this is the first time kirigami has been harnessed to enhance effective adhesion of films on substrates with broad applications ranging from adhesive bandage to wearable electronics.
10:30 AM - *BM09.06.06
Liquid Metals and Hydrogels for Stretchable and Soft Electronics
Michael Dickey 1
1 Department of Chemical ad Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States
Show AbstractThis talk will discuss recent work in our group to use liquid metals as conductors for stretchable, soft, and reconfigurable electronics. Liquid metal alloys of gallium are noted for their low viscosity, low toxicity, and negligible volatility. Despite the large surface tension of the metal, it can be patterned into non-spherical 2D and 3D shapes due to the presence of an ultra-thin oxide skin that forms on its surface. The metal can be patterned by injection into microchannels, by direct-write techniques including 3D printing, and by a number of other methods made possible because the metal is liquid. Also, because it is a liquid, the metal is extremely soft and flows in response to stress to retain electrical continuity under extreme deformation. The ability of the oxide to reform instantaneously also allows the metal to self-heal in response to damage. In addition, the ability to remove the oxide electrochemically provides a new means to control the shape of the metal for reconfigurable electronics. Combining the metal with hydrogels creates electrodes, diodes, and memristor memory devices that are composed entirely out of soft, liquid-like materials. In addition to providing stretchable conductors with the best combination of elongation and conduction, these materials create comfortable interfaces with the skin for non-invasive sensing. The talk will briefly mention recent work, in collaboration with Orlin Velev’s group, for utilizing liquid metals and hydrogels for wearable devices capble of sweat harvesting for biosensing.
11:00 AM - BM09.06.07
Gallium Super-Lyophilic Substrate for Tailored Stretchable Thin Film
Arthur Hirsch 1 , Stephanie Lacour 1
1 , EPFL, Geneva Switzerland
Show AbstractGallium and gallium based alloys have recently gathered a significant interest from the scientific community to design soft, stretchable and reconfigurable electronics. Several methods have been proposed to manipulate and pattern the liquid metal films into elastic conductors but they all lack precise control on the film thickness and roughness thereby limiting its uniformity, stability and reproducibility.
Here we propose a new approach relying solely on wetting phenomena to produce smooth film of pure gallium on extended areas with controlled thickness and electrical properties. We engineered the surface chemistry and topography of silicone rubber (PDMS) to produce gallium super-lyophilic substrates. Physical vapor deposition (PVD) of gallium on such substrates lead to the formation of a smooth and homogeneous film by imbibition of the surface topography. This approach enabled full control on the thickness and resulting sheet resistance of the Ga film.
PDMS substrates decorated with an array of square micro-pillars were prepared by soft lithography and further coated by 60 nm of gold film by sputtering. The choice of the micro-pillars’ dimensions and density defines the imbibition of the microstructured surface by condensing gallium, which is thermodynamically more favorable than coalescence and formation of drops. By capillarity, gallium accumulates in between the pillars up to their top surface, forming a smooth film with an RMS roughness (Rq) smaller than 100nm. We experimentally established the relationship between the aspect ratio of the pillar (h/l, h the height and l the side of the pillar) and the wetting angle on an unstructured substrate (θ0) that should be verified for the stable growth of the Ga film.
We further assessed the electromechanical performance of the films during uniaxial stretching cycles with 4-point resistance measurements and scanning electron microscopy (SEM). The gallium film on the textured substrates displayed significantly lower electrical resistance compared to one on un-textured substrate, and proved highly stretchable (up to 400% max. strain). In addition, we developed an electrical model of the textured film to predict the sheet resistance as function of the geometrical parameters of the pillars. We found good correspondence between the model and experimental measurements. The model can be used to choose the right geometrical parameters of the micro-pillars in order to achieve a desired sheet resistance (e.g. as low as <0.2 Ω/sqr). By providing design criteria and guidelines, this work open new routes for the fabrication of tailored liquid metal stretchable electronic.
11:15 AM - BM09.06.08
Easy and High Throughput Stencil Printing of Liquid Metal Alloy for Stretchable Electronics
Sudipta Sarkar 1 , Debpratim Maji 1 , Chithra Parameswaran 1 , Dipti Gupta 1
1 Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai, MAHARASHTRA, India
Show AbstractIn this work, we present a single step stencil printing method of a liquid metal alloy on elastomeric substrate in order to realize an easy method of fabricating conducting stretchable interconnects. Such electrically conducting stretchable interconnects are crucial components in a stretchable electronic circuit which are of immense importance for biomedical and robotic applications. In the current work, a liquid-phase eutectic gallium indium (EGaIn) based metal alloy was used as stretchable conductor whereas an elastomer polydimethylsiloxane (PDMS) was used for preparing stretchable substrate. For stencil printing, previously prepared stencil mask was firmly placed on semi-cured elastomeric substrate and the liquid metal was rolled over the substrate through stencil masks using a hand roller. The liquid alloy patterns were obtained by slowly peeling the mask off the substrate. Finally the patterns were well encapsulated using another layer of PDMS. Using this method we tried to achieve resolution of the printed patterns till 300 µm. Simultaneous mechanical and electrical testing of such stretchable conducting patterns suggest that the patterns were well able to sustain 35 % of stretching with maximum resistance 5 Ω and 1500 times of stretching cycles with 0.2 Ω variation in resistivity.
11:30 AM - BM09.06.09
Efficient Patterning of Liquid Alloy with Soluble Mask for Stretchable Electronics
Zhigang Wu 1 , Bei Wang 1 2 , Kang Wu 1
1 , Huazhong University of Science and Technology, Wuhan China, 2 , Uppsala University, Uppsala Sweden
Show AbstractThis work reports a method for efficient patterning of liquid alloy by introduction of soluble mask, which not only retain the advantage of large-scale and complex patterning, but also get rid of the time and manpower cost of mask removing before the circuit was encapsulated. The integration of these technological processes suits for mass and automation production.
Stretchable electronics which can take the shape and work reliably in their imposed complicated nonlinear and demanding working environment attract attentions by their unique properties. In order to adapt to production requirement of large scale, high precision and automation. The development of processing technology plays the most basic guidance functions. The technological maturity and feasibility provide the possibility of mass production.
In our work, a soluble PVA compound (polyvinyl alcohol and pigment) mask cut by a commercial available UV (Ultraviolet) laser was applying before liquid alloy atomization spraying. The UV laser helps to the realization of high accuracy and efficiency of mask fabrication. The whole mask is placed in water to remove the unnecessary parts and liquid alloy attached on them after the liquid alloy were atomized sprayed, then it is encapsulated with elastomer when dry up. High resolution with line width fine to 30μm and complicated isolated patterns are proved to be processed in large-scale quickly. More than 10000 cycles are achieved at a maximum strain of 50% in a circuit through our mothed.
Further, a biaxial strain sensor is demonstrated through above process. It proved to be a simplified process suitable for automation production.
11:45 AM - BM09.06.10
Designing Liquid Metal Interfaces for Stretchable Electronic Applications
Sarah Holcomb 3 2 , Jason Heikenfeld 1 , Christopher Tabor 2
3 Department of Materials Science and Engineering, University of Cincinnati, Cincinnati, Ohio, United States, 2 Materials and Manufacturing Directorate, Air Force Research Laboratory (AFRL), Dayton, Ohio, United States, 1 Department of Electrical Engineering and Computer Science, University of Cincinnati, Cincinnati, Ohio, United States
Show AbstractLiquid metal electronic devices have numerous advantages over traditional solid devices, specifically with respect to their ability to be flexed and stretched while maintaining high performance. While mercury had been the commonly utilized liquid metal of use for many years, gallium liquid metal alloys (GaLMAs) have begun to become more popular because of their non-toxic properties, extremely low vapor pressures, and tunable melting point as low as -19°C. Examples of such devices that have been recently demonstrated are wires, switches, polarizers, and antennas. A unique feature of GaLMAs is the mechanically stabilizing and passivating oxide which forms instantly on the surface in as little as 1 ppm oxygen environments. Here we discuss several approaches to designing these interfaces for various applications by chemically controlling the oxide. In some instances, completely removing the oxide is favorable when fluidic behavior is needed, such as to de-wet surfaces and channels1 while in other cases the oxide is useful as a barrier to prevent alloying with electrical connections while contributing minimally to the resistance. It was shown recently that organic molecules such as phosphonic acids or thiols allow for tunability of the mechanical and electrical properties of the interface2. Here, we detail how these approaches address several major obstacles in the field of reliability and repeatability of the GaLMA’s behavior, leading to a more complete understanding of how to integrate liquid metals into stretchable bioelectronic devices.
1. Holcomb, S. et al. Oxide-Free Actuation of Gallium Liquid Metal Alloys Enabled by Novel Acidified Siloxane Oils. Langmuir 32, 12656–12663 (2016).
2. Ilyas, N., Cook, A. & Tabor, C. E. Designing Liquid Metal Interfaces to Enable Next Generation Flexible and Reconfigurable Electronics. Adv. Mater. Interfaces 1700141, 1700141 (2017).
BM09.07: Applications II
Session Chairs
Anastasia Elias
Ingrid Graz
Ivan Minev
Sigurd Wagner
Wednesday PM, November 29, 2017
Sheraton, 2nd Floor, Republic B
2:00 PM - BM09.07.02
A Flexible Thin-Film Resistive and Piezoelectric Tactile Sensor Stack for Robotic Structure Edges
Caroline Yu 1 , Marco Cavallari 1 , Ioannis Kymissis 1
1 , Columbia University, New York, New York, United States
Show AbstractFlexible tactile sensors, typically piezoelectric or resistive, are used to detect applied force and movement [1-4]. Multimodal tactile sensors are currently inflexible and are either silicon-based or combined on printed circuit boards. To overcome this challenge, various flexible tactile sensors have been characterized for absolute and relative force measurements, including multimodal polymer-based sensing skins [5]. Polyvinylidene fluoride (PVDF) is a piezoelectric polymer used for relative movement tactile sensing [3][4]. A metal-PVDF-metal capacitor can measure the charge generated in the PVDF when physically displaced. Several demonstrations in the literature use photolithographic processes to pattern micrometer-sized metal features over large area PVDF [1][2]. For absolute force measurements, typically strain gauges built on elastomer substrates are used [6][7]. Metal deposited onto a thin layer of polydimethylsiloxane (PDMS) can be used to measure large material deformations [8]. In this context, this work presents the material processing and device performance for the combination of two tactile sensor modes placed on top of a compliant layer to increase overall sensitivity. Gold electrodes deposited onto PVDF were used to measure relative displacement, whereas silver-on-PDMS serpentine strain gauges were used for absolute force measurements. PDMS was formed by spin-coating in order to achieve sub-50 micron thick substrates. Photolithography was used for both layers to pattern 25 micron features. For the compliant layer, various thicknesses of PDMS and foam were tested to track changes in sensitivity. The total thickness of layer stack was designed to be less than 200 microns. Uniform force was applied using an Admet eXpert 5600 testing machine to measure force and strain limits. The gold on PVDF measured forces up to 15 N. The silver strain gauges on PDMS had an expected gauge factor of 2.5 and displayed changes in resistance down to 3 % bending induced tensile strain. The multimodal sensor stack demonstrated here adheres to the compliant layer and, therefore, any nonplanar objects. This feature enables the sensing stack to be placed on non-planar surfaces, such as the edges of robotic structures. Obtaining relative (slip) and absolute (normal force) information from the corners and edges of robotic hands will enable feedback for robotic grasping.
2:15 PM - BM09.07.03
Wearable Knitted Strain Sensor Textiles for Wireless Body Movement Monitoring
Shayan Seyedin 1 , Sepehr Moradi 1 , Charanpreet Singh 1 , Jozelito Razal 1
1 Institute for Frontier Materials, Deakin University, Geelong, Victoria, Australia
Show AbstractThere has been a recent surge of interest in the fabrication of wearable devices that exploit the functionality of traditional textiles such as flexibility and wearability, and are capable of sensing body movements at the same time. Traditional strain sensors made of metals or rigid materials, offer limited stretchability, flexibility, and sensing range (typically less than 5 % strain) making them unsuitable for integration within textile structures. Current approaches of making wearable strain sensors mainly rely on coating a small patch of an existing fabric with conducting materials and the textile sensors are typically mounted on supporting frameworks such as elastic substrates, every-day apparels or specially designed frames to perform their sensing functions. Hence, the textile sensors achieved so far were not truly wearable and could not meet the required sensing performance because of unsuitable structures or designs. In this work, we make truly wearable strain sensor textiles from individual fibres with strain sensing functionality. These sensor fibres are fabricated by continuous wet-spinning of composite elastomeric polyurethane (PU) and conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The PU/PEDOT:PSS fibres have 100 filaments and are ~1000 m long and exhibit a high electrical conductivity (~10 S cm-1) and excellent stretchability (~300 %) at 13 wt. % PEDOT:PSS. We knit these fibres into textiles with desired structures and patterns, e.g. plain, co-knit, alternate loops, and stitched. The knitted textiles show strain sensing properties by changing their resistance signals over a large strain range (up to 200 %) and are stable over 500 stretching cycles. Notably, the sensing performance of the textile can be easily tuned by simply changing the textile design. We specifically design knitted strain sensor textiles so that they can be worn on different parts of body such as fingers, elbows, and knees without the need for any support structures. Our wearable strain sensor textiles are then used for remote body movement monitoring by pairing with a wireless transmitter to send the sensing response to a personal computer. The strain sensor textiles developed in this work provide truly wearable sensing platforms that are suitable for applications in medical monitoring, sports rehabilitation, and injury prevention.
3:30 PM - *BM09.07.04
Integrated Autonomous Control for Soft Electroactive Polymer Robots
Iain Anderson 1 2 3 , Katherine Wilson 1 , Jared Pickery-Jordan 1 , E.F. Markus Henke 1 4
1 Biomimetics Lab, Auckland Bioengineering Institute, University of Auckland, Auckland New Zealand, 2 , StretchSense Ltd., Auckland New Zealand, 3 Department of Engineering Science, University of Auckland, Auckland New Zealand, 4 Institute of Solid State Electronics, TU Dresden, Dresden Germany
Show AbstractLiving muscles that control animal crawling, wing flapping, and enteric wave-like gut contraction are largely coordinated by localized autonomous neural networks, also known as central pattern generators (CPGs). These networks can provide muscle firing order and timing control, without the need for intervention from higher brain centres. Thus local control by CPG reduces the overall control burden on the animal’s central nervous system. Synthesizing key aspects for such a distributed control architecture could provide a basis for the control of soft, multi-degree-of-freedom robots.
We have synthesized key aspects of CPG operation through the use of dielectric elastomer electroactive polymer technology. Specifically we have developed the dielectric elastomer oscillator (DEO), as a direct analogue for the CPG, built up from dielectric elastomer (DE) actuators and piezoresistive dielectric elastomer switches (DES). A DEO is assembled from an odd number of coupled soft inverters, each of which includes a resistor and a DE artificial muscle actuator physically coupled to a soft polymer piezoresistive DES. For each inverter the delivery of high voltage charge to the DE actuator at the input will produce in-plane expansion. Expansion of the muscle compresses its DES, reducing the electrical resistance across it by several orders of magnitude. The output of the inverter, effectively the voltage potential across the DES will now be low. It follows that low potential at the input (no charge on DE actuator) will result in high potential (across its DES) at the output. Coupling an odd number of these inverters in a closed loop will produce an oscillator that can be used to feed charge to DE muscles with a self-excited periodicity and, hence, control and drive biomimetic robotic structures. The DEO can be fully integrated within the soft robot: muscles that produce the timing of charge delivery can also serve as active muscles for crawling and wing flapping.
DEO with frequencies in the range (0.02 – 15 Hz) have been built and used for the control of crawling and wing-flapping robotic demonstrators. By tuning the printed charging resistors, it is possible to set and change the oscillation frequency of DEOs. Further improvement in materials and production technology will lift this benchmark.
All parts can potentially be ink jet printed, heralding the manufacture of printable biomimetic robots composed entirely of polymer and carbon. Future work includes exploration of higher order control of rhythmic CPG-like activities. In this way we will mimic the control architecture of living animals and further advance control for soft robots.
4:00 PM - BM09.07.05
A Soft Total Artificial Heart—A Novel Approach towards Heart Replacements Using Soft Robotics Principles
Nicholas Cohrs 1 , Anastasios Petrou 1 , Michael Loepfe 1 , Christoph Starck 2 , Marianne Schmid Daners 1 , Mirko Meboldt 1 , Volkmar Falk 2 , Wendelin Stark 1
1 , ETH Zurich, Zurich Switzerland, 2 , Deutsches Herzzentrum Berlin, Berlin Germany
Show AbstractHeart failure (HF) is one of the world’s most significant diseases. It concerns more than 26 million people worldwide and reaches a share of 30% of all deaths. As the number of donor hearts is limited, the use of artificial blood pumps for HF patients is continuously increasing. Currently most implanted artificial hearts are so called ventricular assist devices (VAD), which support and relieve the weakened heart. In principle, these VADs are very basic pumps, which produce a continuous blood flow, rather than a physiological pulsatile one. This is intrinsically unnatural and possibly unhealthy, as the consequences of missing blood flow pulsatility remain unknown. In great contrast to the current focus on VAD technologies, we developed a total artificial heart using soft robotics principles, thus imitating the human heart in its resemblance, mechanical properties and way of pumping (i.e. by squeezing the blood). Using a 3D-printed mould and a lost-wax casting technique, it is possible to manufacture an entirely soft total artificial heart (sTAH), which is made of one single silicone elastomer monoblock and, in contrast to existing VADs, is completely soft [1, 2]. This technology, adapted from soft robotics aims at replicating the biomimetic motion of the human muscular system [1, 3, 4]. The sTAH mimics the human heart from a physiological and physical motion point of view, yielding pulsatile blood flow [1, 4]. Soft robotics technology could enable a first step towards personalized implants in artificial blood pump therapy [1]. Evaluation of the sTAH against physiological pre- and afterloads of the human circulatory system using a hybrid mock circulation [5] revealed a physiological pressure waveform, which is very similar to the one of the human heart. An aortic pulse pressure of 35 mmHg was reached, which is to our knowledge one of the most physiological pulse pressure, compared to any other artificial heart or VAD. Against a physiological afterload, the sTAH reaches a left ventricular flow of 2.2 L/min with a systolic/diastolic pressure of 71 to 36 mmHg. Vast improvements are feasible by using alternative elastomeric materials, optimization of the pneumatic drive and optimization of the chamber geometry.
[1] N.H. Cohrs, A. Petrou, M. Loepfe, M. Yliruka, C.M. Schumacher, A.X. Kohll, C.T. Starck, M. Schmid Daners, M. Meboldt, V. Falk, W.J. Stark, doi.: 10.1111/aor.12956.(accepted for publication)
[2] C.M. Schumacher, M. Loepfe, R. Fuhrer, R.N. Grass, W.J. Stark, RSC Adv 4(31) (2014) 16039-16042.
[3] F. Ilievski, A.D. Mazzeo, R.F. Shepherd, X. Chen, G.M. Whitesides, Angew Chem Int Ed 123(8) (2011) 1930-1935.
[4] E.T. Roche, R. Wohlfarth, J.T.B. Overvelde, N.V. Vasilyev, F.A. Pigula, D.J. Mooney, K. Bertoldi, C.J. Walsh, Adv Mater 26(8) (2014) 1200-1206.
[5] G. Ochsner, R. Amacher, A. Amstutz, A. Plass, M. SchmidDaners, H. Tevaearai, S. Vandenberghe, M.J. Wilhelm, L. Guzzella, IEEE Trans Biomed Eng 60(2) (2013) 507-516.
4:15 PM - BM09.07.06
VCSEL-Based Stretchable Blood Flow Sensors
Dongseok Kang 1 , Haneol Lim 1 , Jae-Won Nam 2 , Mike Shuo-Wei Chen 2 , Jongseung Yoon 1 2
1 Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California, United States, 2 Department of Electrical Engineering, University of Southern California, Los Angeles, California, United States
Show AbstractRecently, real-time monitoring of physiological information using skin-affixed wearable sensors has become increasingly popular for early intervention of chronic diseases or prevention of acute illnesses. In particular, blood flow in small vessels or microvascular perfusion is an important indicator for detecting the reduction of local blood flow and diagnosing peripheral vascular disease. Among various methodologies developed so far, fiber-optic-based laser Doppler flowmetry (LDF) has been widely used for measuring dynamic changes in microvascular blood flow in specific areas of the skin. However, several critical limitations in this technology including bulky instrumentation and sensitivity to the motion of subjects have hampered its applications for continuous health monitoring in wearable formats. Here we present stretchable laser Doppler sensors that can be affixed onto the skin to measure microvascular blood perfusion in a real-time, continuous manner, where vertical cavity surface emitting lasers (VCSELs) were employed as a monochromatic, coherent light source. Microscale VCSELs and GaAs-based photodiodes (PDs) were heterogeneously assembled on an elastomeric substrate by transfer printing. The co-integrated VCSEL and PD exhibited excellent optoelectronic properties in levels comparable to those on the growth substrate owing to mechanically, thermally, and optically optimized configurations, which was translated to the excellent sensing capabilities under various deformation conditions.
4:30 PM - BM09.07.07
Highly Stretchable Implantable Device for Bladder Volume Monitoring and Stimulating
Dongxiao Yan 1 , John Seymour 1 , Yuting Wu 1 , Chris Stephan 2 , Alex Mundorf 2 , Yu-Heng Cheng 1 , Tim Bruns 2 , Euisik Yoon 1
1 Department of Electrical and Computer Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractUrinary retention due to an inability to effectively contract the bladder can occur after a variety of neurologic and non-neurological events such as spinal cord injury, stroke, diabetes, and aging. Bladder emptying can be assisted or controlled by electrical stimulation on the bladder wall. In this work, we developed a direct bladder interface by building an implantable device with multi-layer Ecoflex (Smooth-on®, Inc.) silicone, carbon nanotube (CNT) and metal structures which are capable of strain sensing and detrusor muscle stimulation.
The bulk of the device is built by Ecoflex 00-50, of which the biostability and minimal reactivity in vivo is very promising (Park, et al., 2014). Furthermore, the mechanical tests showed that the modulus of elasticity measured on a device is ~1/5, at 50% strain, and <1/10, at 100% strain, of it measured on a similarly-sized pig bladder section. Thus our developed devices should cause minimal distortion of the bladder when expanding and contracting. Highly stretchable conductors are achieved by forming CNT percolation networks, where ~1-μm thick carbon nanotube film is deposited and patterned by spray coating over a shadow mask. Strain sensing mechanism using CNT capacitors has been demonstrated (Cohen, et al., 2012) but this is the first work to our knowledge to test on pig bladders with stimulation-driving channels and in soaking conditions.
Importantly, we developed a device and assembly technique that allows for fine medical grade wires to interface with our bladder stimulation/strain sensor array. To achieve a stable connection, we first stacked a Ti/Au layer by evaporation onto the CNT layer. Then a thin layer of silver paste was applied to form a thermal barrier. Finally, solder paste reflow allowed the attachment of wires. The backend was then secured with medical grade epoxy to prevent the bond pads from undergoing significant strain.
We studied the reliability of the device (including wires) in a saline environment by soaking at 0, 1, 3, 12 and 24 hours. Only a small fluctuation of resistance < ±5% was observed during this process, which demonstrated the stability of the electrical properties of the wire-metal-CNT connection and the CNT percolation networks in an acute setting. Bench-top testing showed a reversible change of resistance, △R/R, from 0% to 485% over the corresponding strain from 0% to 100%. The volume of the bladder is indirectly estimated from the piezoresistive response of this CNT resistor. An ultimate embodiment will use a pre-defined strain level to trigger circuits that stimulate bladder muscles through the electrodes on the device. In preliminary ex vivo experiments, devices were sutured tightly to a fresh pig bladder. During bladder normal filling and emptying the devices were stretched up to ~50% strain with no failures at suture sites. A comprehensive ex vivo study, in vivo evaluations, and functional analyses for longer soaking times and more stretching cycles will be performed.
4:45 PM - BM09.07.08
Artificial Touch—Actuating Fine Textures in Haptic Devices
Charles Dhong 1 , Darren Lipomi 1
1 , University of California, San Diego, La Jolla, California, United States
Show AbstractOur sense of touch is an important part of how we interact with the world. Despite its importance, relatively little is known about the mechanics at the interface between a finger and an outside surface, let alone controlling that interface purposefully. We have found that humans can reliably differentiate between flat surfaces that have been coated with either a hydrophilic (plasma-treated) or hydrophobic (silanized) layer by sliding their fingers across the surfaces. We translated these findings into a flexible, low voltage, wearable device that modulates the friction at the fingertip in a specific manner that is not addressed with current vibration or variable friction technologies. Our device has a variable-friction “active layer” that lays on top of an “actuation layer”. This allows us recreate the equivalent motion of a finger moving on stationary surface and electrically modulate a crucial component of fine texture on demand. This modular, layered device allows for future functionality as well. Finally, the mechanical flexibility of these layers is essential for 1) conformal contact to a finger, 2) deployment in a glove form factor and 3) micropatterning for scalability and finer sensation control.
BM09.08: Poster Session II: Stretchable Bioelectronics
Session Chairs
Anastasia Elias
Ingrid Graz
Ivan Minev
Thursday AM, November 30, 2017
Hynes, Level 1, Hall B
8:00 PM - BM09.08.01
Fully Stretchable Thin-Film Bioelectronics for Wearable Display and Cardiac Mapping
Jia Liu 1 , Yuxin Liu 2 , Francisco Molina-Lopez 1 , Jiechen Wang 1 , Nathan Wang 1 , Anson Lee 3 , Zhenan Bao 1
1 Chemical Engineering, Stanford University, Stanford, California, United States, 2 Bioengineering, Stanford University, Stanford, California, United States, 3 Department of Cardiothoracic Surgery, School of Medicine, Stanford University, Stanford, California, United States
Show AbstractDevelopment of high-performance electronics that can intimately and seamlessly integrate with human bodies and biological systems at the cellular level is the key for the next generation consumable wearable electronics and biomedical devices, which requires the device to possess biosystem-compatible mechanical and chemical properties. Recently, intrinsically stretchable polymeric electronic materials including semiconductors, conductors and dielectrics are intensively reported and considered as ideal candidates for such applications given their unique electrical and mechanical properties. However, the porous structures and poor chemical resistance prevent intrinsically stretchable polymeric materials to be integrated into functional electronics (e.g. thin-film transistor array) through the conventional fabrication process. Here, we present the first fully stretchable thin-film transistors and electrodes array through patterning of intrinsically stretchable semiconductors and conductors. To enable this solution-processed fabrication, we invented a new perfluorinated dielectric material that is 1) extremely tolerate to the most organic solvent for the fabrication, 2) directly photopatternable with sub 10 µm feature size by conventional lithographer and a chemically orthogonal development process and 3) highly stretchable with > 200% stretchability. In addition, we have developed an ink containing conjugated semiconducting polymer with siloxane-azide crosslink for the inkjet-printing patterning of the semiconductor and lithographic patterning of stretchable PEDOT:PSS. Using perfluorinated dielectric material as the substrate, dielectric layer and passivation, we can achieve the direct, reliable pattern of intrinsically stretchable semiconductor and conductor into the transistor/sensors array with record-high active materials coverage, device yield and device density, and ultra-high stability in chemical and biological solutions. The electrical and mechanical characterizations show that the transistors and sensors array kept its original performance without significant degradation under 100% uniaxial strains and through multiple cycles. As the initial demonstration, the stretchable transistors/sensors array has been used as the backplane for fabrication of fully stretchable light-emitting diode (LED) array for the wearable display and as implantable biomedical devices for the epicardial arrhythmogenic activity mapping. We believe this unique dielectric materials and fabrication process can be applied to virtually any stretchable materials and impact on the low-cost fabrication of fully stretchable electronics for wearable and biomedical device in the industry.
8:00 PM - BM09.08.02
Self-Assembling of Nanomaterials via Droplet Manipulation for Multifunctional Electronics
Meng Su 1 , Yanlin Song 1
1 , Institute of Chemistry, Chinese Academy of Sciences, Beijing China
Show AbstractThe ability to rapidly and precisely construct multifunctional electronic and optic devices would enable myriad applications, including displays, solid-state lighting, wearable electronics and biomedical devices with embedded circuitry. Here, the droplet manipulation strategy is demonstrated for rapidly patterning materials over a broad range of compositions and accurately achieving the correct position at the micro- and nanoscale. One spontaneous process was designed to assemble nanoparticles into optimal interconnect between certain nodes on diverse substrates, as natural systems spontaneously figuring out the shortest path1. The resulted pattern with the shortest interconnect through the manipulation of droplet, has the minimum free energy at the thermodynamic equilibrium. The optimal interconnect leads to a 65.9 percent decrease in the electromagnetic interference, a 17.1 percent decrease in the delay and a 24.5 percent decrease in the energy-delay. One feasible strategy was demonstrated to assembly nanoparticles into micro or nano curves2. The curves with various tortuosity morphologies have differential resistive strain sensitivity, which can be integrated to multi-analysis flexible sensor. The printable curves sensor performed sensitive and stable resistance response on deformations, which could run complicated facial expression recognition, and contribute the remarkable application on skin micromotion manipulation auxiliary apparatuses for paraplegics.
Reference:
1. Meng Su, et al. Swarm intelligence-inspired spontaneous fabrication of optimal interconnect at the micro/nanoscale. Adv. Mater. 2017, 29, 1605223.
2. Meng Su, et al. Nanoparticle based curve arrays for multirecognition flexible electronics. Adv. Mater. 2016, 28, 1369-1374.
8:00 PM - BM09.08.03
From Waste Paper to Multifunctional Wearable Device
Yuan-Qing Li 1 , Shao-Yun Fu 1
1 College of Aerospace Engineering, Chongqing University, Chongqing China
Show AbstractWearable devices that can be used to monitor personal health, track human motions, and provide thermotherapy etc. are highly desired in personalized healthcare. In this work, a multifunctional wearable “wrist band” which works as both heater for thermotherapy and sensor for personal health and motion monitoring is fabricated from a flexible and conductive carbon sponge/polydimethylsiloxane (CS/PDMS) composite. The key functional material of the “wrist band”, namely the conductive CS, is synthesized from waste paper by a freeze-drying and high-temperature pyrolysis process. When the “wrist band” works as a heater under 15 V, a stable temperature difference of 20 oC is achieved between the “wrist band” and the ambient. When the “wrist band” serves as a wearable strain sensor, the “wrist band” exhibits fast and repeatable response, and excellent durability within the strain range of 0-20% and the working frequency of 0.01-10 Hz. Finally, the typical applications of the multifunctional wearable “wrist band”, as a heater for thermotherapy, and a sensor for blood pulse, breathe, and walk monitoring, are demonstrated. Due to its low cost, high flexibility, moderate conductivity, and excellent strain sensibility, the as-prepared wearable device based on the CS/PDMS composite is promising to be applied for the provision of personal healthcare.
8:00 PM - BM09.08.04
Bubble Lithographic Electoless Bespreading (BLEB) Technique for Mesh Metal Electrodes
Hiroya Abe 1 , Tomokazu Matsue 1 , Hiroshi Yabu 1
1 , Tohoku University, Sendai Japan
Show AbstractTransparent electrodes are an essential component in numerous electronic devices, such as displays, solar cells, touch screens, light-emitting devices, and wearable devices. Particularly, wearable devices have rapidly emerged with reseaches of flexible and transparent devices.
We previously reported that honeycomb-patterned polymer films were (honeycomb films) generated by using condensed water droplets as templates during solvent evaporation from polymer solutions1. Porous electrodes have been prepared by electroless deposition of silver onto polystyrene honeycomb films2. However, due to the thick metal film formation, the film did not transmit the light high enough to apply them to flexible devices.
In this study, we report the preparation of mesh metal electrodes deposited only on a top of the honeycomb films by electroless deposition under Cassie-Baxter wetting state, which technique is named as “Bubble Lithographic Electoless Bespreading (BLEB)”. The mesh metal electrodes had higher transparency than the honeycomb electrodes with fully deposition of metal.
Honeycomb films of polystyrene prepared on PET substrates were fabricated by using the Breath Figures method1. In order to deposit Cu metal on the top of honeycomb films, the films were immersed to catalyst, reduction and Cu deposit solution in order. In order to obtain the fully metal-deposited honeycomb films, the films were immersed to ethanol for 1 min before the electroless deposition. The honeycomb films were characterized by optical microscope, and transmission electron microscope (TEM).
The prepared honeycomb film had a hexagonal structure whose diameter of pores was c.a. 5 μm. After an electroless deposition for 10 minutes on the honeycomb films, the films have a metallic luster, and which indicates that Cu metal was deposited on the films. From cross-sectional TEM observation, whereas Cu metal was deposited only on the top of honeycomb films, Cu metal on entire honeycomb films with ethanol treatment. In the case without the ethanol treatment, the honeycomb film kept the Cassie-Baxter state, in which air bubbles are trapped in the honeycomb films during electroless deposition due to hydrophobic property of the films. In the other case (ethanol treatment), the Cassie-Baxter state changed to Wenzel state because the air pockets of the films were filled by ethanol and the solution can be able to penetrate into the pockets. The transparency of the metal-deposited films was characterized by bare eyes, and the transparence of the films without the ethanol treatment was clearly higher than the films with the treatment. The conductivity of the films were almost no difference between those films (approximately 10 Ω). Since the conductivity was not changed by bending the films, these results indicate that the films have high flexibility.
1) H. Abe et al., Macromolecular Materials & Engineering, 2016, 301, 523-529
2) H. Yabu et al., Langmuir, 2006, 22, 9760–9764
8:00 PM - BM09.08.05
Omnidirectional Bending and Pressure Electronic Skin Based on Stretchable CNT-PU Sponge
Haotian Chen 1 , Zongming Su 1 , Yu Song 1 , Haixia Zhang 1
1 , Peking University, Beijing China
Show AbstractNowadays, with rapid developments of electronic technologies and computer science, robots are expected to be widely used in various fields, such as industry, rehabilitation assistance and even household. In order to complete dexterous manipulation and interaction tasks, robots need to possess more powerful sensing abilities to behave more like human. For human beings, bending and pressure detection are the most common movement in daily life. Development of effective multi-functional sensor becomes an urgent problem to be solved. However, recently reported bending sensors only focus on detecting bend in a single direction, such as finger bending detection, which seriously hinders their applications in detection of more complex multidimensional bending conditions. Actually, both of bending curvature and direction are important parameters for establishing hominoid electronic sensor, whose significance is often ignored. Moreover, piezoresistance bending sensor usually suffer from the interference from external pressure, because both of bending and pressure can make resistance to change.
In this work, a stretchable and multi-functional sensor, which can detect omnidirectional bending and pressure independently, has been demonstrated. The sensor is composed of two orthogonal functional layers, each of which consisting of a carbon nanotube - polyurethane sponge strips (CPSS) and a PDMS substrate. A simple and low-cost method has been proposed in the device fabrication. The porous structure make is sensitive both to bending and pressure. The electrical property can be easily controlled by concentration of CNT ink and dip time. As a single CPSS has different sensitivities in different bending directions due to its shape, two perpendicular CPSSs are stacked up together to complement the information of bending distances and bending directions at the same time. Based on standard experimental test data, a universal function set has been built up, in which, both of the bending distances and bending directions can be directly obtained with negligible error from two resistances of the double-layer sensor. As bending is a very common action in human motion, this omnidirectional bending sensor is very useful for detecting human motion of multiple degrees of freedom.
Moreover, both pressure and bending can change the resistance, which usually causes confusion when the resistance changes. In this work, we take advantage of triboelectric effect as a mark signal, to make this sensor easily differentiate pressure and bending Due to the contact electrification effect, the motion of pressure will cause the charge to recontribut according to the triboelectric sequence thus generating a current flowing from the device to the ground working as a single-electrode triboelectric generator. In this way, the pressure and bending can be effectively distinguished and supply omnidirectional information of pressure and bending without confusion.
8:00 PM - BM09.08.06
Estimation of Ion Dimension Doped in Conducting Polymers Electrochemically
Keiichi Kaneto 1 , Fumito Hata 1 , Sadahito Uto 1
1 Department of Biomedical Engineering, Osaka Institute of Technology, Osaka Japan
Show AbstractConducting polymers can be electroactive materials in soft actuators (artificial muscles) driven by electrical stimulation. The actuation is generated upon electrochemical oxidation of the film in an electrolyte solution, due to insertion of bulky counter ions (dopant ions). The magnitude of deformation depends on the degree of oxidation and the size of dopant ions solvated (Stokes radius). It is worthwhile to know the detailed relationship between the magnitude of deformation and ion dimension.
The magnitude of deformation, Δl/l0 (Δl: change of film length, l0: original film length) during electrochemical oxidation and reduction, is precisely measured using a laser displacement meter and a handmade apparatus. From the values of Δl/l0, electrical charges put in the film during oxidation and the film dimension (length x width x thickness) the radius of dopant ions can be evaluated, assuming the isotropic expansion of film.
Polypyrrole films for anion drive were electrodeposited in electrolyte solution of pyrrole, methylbenzoate and TBABF4, and electrochemically cycled in aqueous electrolytes of NaCl, NaBr, NaNO3, NaBF4 and NaClO4. The dopant ionic radii of Cl-, Br-, NO3-, BF4- and ClO4- were estimated to be 230, 244, 248, 269 and 289 pm, respectively. These radii are basically between those of salt crystals and hydration radii. The results will be discussed with the detail experimental procedure and analysis, as well as cation radii of Li+, Na+ and K+ in cation drive films.
8:00 PM - BM09.08.07
Hydroprinting of Conductive Patterns onto 3D Structures for Stretchable Electronics
Michael Layani 1 , Shlomo Magdassi 1 , Gabi Saada 1
1 , The Hebrew University of Jerusalem, Jerusalem Israel
Show AbstractFabrication of functional electronics onto 3D surfaces can be a very costly process when using 5 axis systems or very cumbersome and limiting for other stamping based methods. A Novel method for printing functional conductive patterns on three dimensional objects with unconventional angles using hydroprinting of conductive patterns was developed. The conductive patterns were printed on water soluble polyvinyl alcohol (PVA) films followed by post printing processes to optimize the conductivity. The conductive patterns are then hydroprinted on hard 90° angle objects and can be assembled without any presence of sacrificial layer,
which allows layer-by-layer sequential hydroprinting. In addition, electric Light Emmiting Diode (LED) circuits and heater were successfully hydroprinted. To show the applicability of the process we hydroprinted a fully functional Near Field Communication (NFC) antenna onto a curved object, which was successfully paired with a smartphone.
The process enables printing of functional materials onto 3D structures, without the need for costly equipment and complicated processes. The whole process takes only a few minutes due to tailoring of the PVA composition, and can be performed using a variety of materials ranging from metal nanoparticles to carbon nanotubes and silver nanowires for stretchable objects.
*Saada, G., Layani, M., Chernevousky, A. and Magdassi, S., 2017. Hydroprinting Conductive Patterns onto 3D Structures. Advanced Materials Technologies, 2(5) 2017.
8:00 PM - BM09.08.08
Stretchable Organic Light-Emitting Diodes on Elastic Pillars with Plates Connected by Coplanar Serpentine Bridges
Myung Sub Lim 1 , Young Hyun Son 1 , Kyung Cheol Choi 1
1 , KAIST, Daejeon Korea (the Republic of)
Show AbstractThe rapid development of flexible electronic technology that allows devices to be lightweight, break-resistant, bendable and foldable facilitates portability and ease of use compared to rigid and thick devices. At the same time, interest in wearable electronics has increased explosively, and stretchable electronic technology that can overcome the flexibility limitations of plastic or fabric substrates and ultimately withstand mechanical stress under a variety of conditions, such as bending, folding, twisting, and stretching, has received considerable amounts of attention in recent years. However, compared to the development of stretchable electronics, technology related to stretchable lighting devices remains underdeveloped. Various demonstrations of stretchable lighting devices have been presented, but such devices are highly restrictive because they depend on new materials or specific technologies as opposed to existing base technology.
In this study, we fabricate a substrate that can withstand mechanical stress caused by bending and the elongation of elastic materials with an OLED thermally deposited on the substrate to make the devices stretchable. Conventionally, elastic lighting devices require new materials and new structures, but in this study we implement a stretchable substrate and OLEDs using general processes and materials which rely on a structural change of the substrate. A structure capable of withstanding mechanical stress is created by combining a protruding columnar array of PDMS, which is an elastic material, and plate and bridge structures consisting of SU-8, which is a rigid material. Due to external mechanical stress, the PDMS and SU-8 bridge structures are stretched to enable the substrate to be elongated, and the OLEDs emit light onto the SU-8 plate structure to which the bridge structure is connected. The SU-8 plate structure supported by the PDMS column array has the function of isolating the mechanical stress externally as much as possible, thereby securing the stability of the OLED emission. In addition, this substrate has a simple structure and fabrication process that can be universally applied as a stretchable device rather than a substrate limited to the operation of OLEDs. The advantages and disadvantages of this substrate were confirmed using ANSYS, a mechanical simulation tool, when manufacturing the substrate structure and operating the OLEDs.
The substrate has simple process steps and structures that can be applied to stretchable OLEDs as well as stretchable devices. Regarding the bridge or wiring structures, previous studies demonstrated the driving of inorganic light-emitting diodes in relation to stretchable devices, but few studies have described the fabrication of devices via the deposition of OLEDs.
8:00 PM - BM09.08.09
Ultra-Flexible Organic Optical Devices for Pulse Monitor
Tomoyuki Yokota 1 , Martin Kaltenbrunner 1 2 , Hiroaki Jinno 1 , Naoji Matsuhisa 1 , Hiroaki Kitanosako 1 , Wakako Yukita 1 , Mari Koizumi 1 , Takao Someya 1
1 , The University of Tokyo, Tokyo Japan, 2 Soft Matter Physics, Lintz Institute of Technology, Linz Austria
Show AbstractOptoelectronic devices are critically important in medical field since these devices can non-invasively detect bio-signals and other clinical information. Recently, organic light-emitting diodes (OLEDs) and organic photo detectors (OPDs) were separately manufactured on glass and bulky (less than 1 mm) plastic substrates, and later combined to form a transmission-mode pulse oximeter [1] and muscle contraction sensor [2]. Previously, we reported on developing ultra-flexible PLEDs and OPD on 1.5-µm-thick films. By integrating ultra-flexible green and red PLEDs with an OPD, highly flexible and conformable reflective pulse oximeter has been demonstrated. This pulse oximeter was laminated on skin using adhesive tape with a thickness of 6 µm. The total thickness was approximately 30 µm [3].
Here, we are reporting on developing an ultra-flexible and conformable pulsimeter, by integrating a green PLED and an OPD on the same substrate, with the total thickness of only 6 µm. In order to detect pulse waves, the device was turned upside down and wrapped around a finger. With the driving voltage of the PLED set at 5 V, the pulse was monitored by measuring the open-circuit voltage (Voc) of the OPD, which indicates the absorption of green light in the blood. Due to the reduction of the individual device thickness (3 µm each) and placement of the active layer in the neutral strain position, our ultrathin PLEDs and OPDs show very good mechanically flexibility, surviving bending and crumpling down to 100 µm bending radius.
This work was supported by the Someya Bio-Harmonized ERATO grant.
[1] C. M. Lochner, Y. Khan, A. Pierre, and A. C. Arias, Nature Commun. 5, 5745 (2014).
[2] A. K. Bansal, S. Hou, O. Kulyk, E. M. Bowman, and I. D. W. Samuel, Adv. Mater. 27,7638, (2015).
[3] T. Yokota, et al., Science advances, 2, e1501856 (2016).
8:00 PM - BM09.08.10
Selective Activation of Liquid Metal Nanoparticle Films via Laser-Sintering
Shanliangzi Liu 1 2 , Michelle Yuen 1 2 , Biwei Deng 1 , Edward White 1 , J. William Boley 3 , Rebecca Kramer 2
1 , Purdue University, West Lafayette, Indiana, United States, 2 , Yale University, New Haven, Connecticut, United States, 3 , Harvard University, Cambridge, Massachusetts, United States
Show AbstractGallium-indium alloys have been used to create flexible and stretchable electronics. Several approaches to processing gallium-based liquid metals have been demonstrated, including injection into microchannels, direct writing, masked deposition, and embedding microscopic inclusions in an elastomer matrix. To be compatible with scalable manufacturing techniques, we previously demonstrated printing liquid metal nanoparticles in a carrier solvent. In our previous work, we employed mechanical sintering to coalesce deposited liquid metal nanoparticles to create conductive paths. In this talk, we present laser sintering, a promising method to improve resolution, scalability, speed and stability of liquid-metal-based soft electronics. We produce liquid metal nanoparticles with sonication times ranging from 120 min to 960 min, and spray print the inks on the substrates. We study the effects of laser power, particle size, film thickness and substrate hardness on electrical resistance of laser activated traces. We demonstrate that laser sintering of liquid metal particles is possible on soft surfaces, which has not been achieved previously with mechanical sintering. We also show that laser sintering works for liquid metal particles smaller than 70 nm, which indicates the possibility of manufacturing mass-producible soft electronics through inkjet printing. To understand more about the laser sintering mechanism, we compare the relative contributions of oxide ablation using focused ion beam lithography and thermal effects using a heated furnace. This talk concludes with the demonstration of printed flexible and stretchable electronic devices activated by laser sintering.
8:00 PM - BM09.08.11
Super-Stretchable, Transparent and Fatigue-Free Metal Nanomesh Electrodes
Chuanfei Guo 1
1 , South University of Science and Technology of China, Shenzhen China
Show AbstractFlexible electronics is an emerging field that attracts increasing attentions. Flexible transparent electrode is a key element in flexible electronic devices, while a challenge in this field is to make electrode not only bendable, but also stretchable, even under cyclically stretching. A material that is optically transparent and electrically conducting is often not stretchable. However, a transparent conducting film can become stretchable if it is tailored to some certain geometry, such as a network, or serpentines. The design of geometry has been a powerful method to investigate highly stretchable and transparent electrodes. In this talk, we have used an unconventional method that we call grain boundary lithography to make a gold nanomesh with serpentines. We also find that the interfacial strength of the metal nanomesh/polymer bilayer is critical to the stretchability and fatigue-resistance. A gold nanomesh with an optimized topology and adhesion exhibits super-large stretchability and low strain fatigue: it can be stretched to 300% while showing a sheet resistance and a transmittance superior to those of commercial indium tin oxide films, and it can be stretched to 150% for 50,000 cycles without showing fatigue. The electrode also shows good biocompatibility. Such an electrode is an ideal platform for highly stretchable photoelectronics, implantable electronics and e-skins.
8:00 PM - BM09.08.12
Engineering Poisson’s Ratio of Soft Materials through Geometric Design of Auxetic for Highly Sensitive and Conformable Strain Sensor
Young-Joo Lee 1 , Seol-Min Yi 1 , Seung-Min Lim 1 , Jeong-Ho Lee 1 , Jeong-Yun Sun 1 , In-Suk Choi 2 , Young-chang Joo 1
1 , Seoul National University, Seoul Korea (the Republic of), 2 , Korea Institute of Science and Technology, Seoul Korea (the Republic of)
Show AbstractSoft materials have been highlighted because of their good compatibility with smart devices such as stretchable electronics, soft robotics, self-healing materials, camouflaging materials and so on. The soft materials have compliant behavior, i.e. low Young’s modulus, and high Poisson’s ratio originated from their bonding nature. However, because soft devices are made of various materials, the difference in mechanical properties of soft materials in compared to other material class, e.g. metal thin films, conducting polymers, could induce interface instability, resulting in earlier mechanical failure. Also, conformal attachment on human body is still one of critical problems for epidermal electronics. It can be a radical solution for soft materials to have controllability of the Poisson’s ratio, however, it is difficult to control the Poisson’s ratio without synthesis of new materials.
In this study, a new approach to meet requirements of soft materials is suggested by geometric design concept. . By controlling Poisson’s ratio through fabricating composite material made of auxetic structure and soft material, a new material which has negative Poisson’s ratio and with continuous surface was developed. Moreover, Poisson’s ratio of our developed material could be predictively tuned by geometric design of auxetic structure. Based on good compatibility to the integration of devices, the characteristic of 2-dimensional auxetic composite was applied to capacitive strain sensor for overcoming theoretical limit. Additional guide for designing composite material will be discussed based on FEM calculations.
8:00 PM - BM09.08.13
Enhancing the Macromolecular Orientation and Electrical Output of Electrospun PVDF-HFP Nanofibers through Post-Draw Processing
Adriano Conte 1 , Harrison Hones 1 , Shirvani Khosro 1 , Raghid Najjar 1 , Hu Xiao 1 , Wei Xue 1 , Vince Beachley 1
1 , Rowan University, Glassboro, New Jersey, United States
Show AbstractThe recent growth in portable electronics has sparked a demand for alternative energy sources. Energy harvesters that utilize piezoelectric materials are promising in capturing the mechanical energy from body movement to power portable electronics. This study investigated the characteristics of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) nanofibers created from traditional electrospinning and an automated track electrospinning technique that includes post-draw processing. The solution was initially processed using the traditional method, flat-plate electrospinning, which resulted in a fiber network with random orientations. When performing electrical testing these fibers produced minimal voltage. The solution was then processed utilizing a post-drawing electrospinning technique, unique to our laboratory, that allowed for fiber alignment and individual nanofiber post-drawing immediately upon deposition, before complete solvent evaporation. Fibers that underwent post-drawing demonstrated an increase in beta vs. alpha phase ratio and an increase in crystal alignment in the direction of the fiber axis (confirimed by polarized FTIR) and produced higher voltages than undrawn fibers and fibers from the traditional electrospinning method. It was observed that fibers processed using the post-drawing technique with different draw ratios (DR=Final length/Initial length) such as DR 2 and DR 3 showed enhanced piezoelectric properties. This research suggests that the post-drawing process results in PVDF-HFP nanofibers that are better suited for piezoelectric applications than traditionally electrospun nanofibers.
8:00 PM - BM09.08.14
Low-Temperature Curable Conductive Pastes for Stretchable Electronic Devices
Ho Sun Lim 1
1 , Sookmyung Women's University, Seoul Korea (the Republic of)
Show AbstractWe have presented a development of low temperature-curable epoxy-based electrically conductive pastes for flexible substrates. Electrically conductive pastes are composed of a novolac epoxy resin and a trimodal metallic mixture of micron-sized silver flakes, silver microspheres, and silver nanoparticles, followed by curing of epoxy resin at relatively low temperatures. The conductive silver fillers made the pastes electrically conductive due to their metal-to-metal bonding, whereas the epoxy resins used for an improvement of a processability and adhesion between the metal surface and conductive pastes. Silver nanoparticles were also used as a supplementary filler to improve the metallurgical adhesion between conductor traces into the epoxy matrix. In this study, our strategy is to add reactive silver precursors to form the good metallic network of the conductive materials and reduce curing temperatures of the conductive pastes. As a result, we found that volume resistivity and electric conductivity of our epoxy-based conducting pastes containing the reactive silver precursors exhibited high values of 2.5 X 10-5 Ωcm and 4.0 X 104 S/cm, respectively, even at a low curing temperature of 150 °C. The resulting high conductivity may be used for a fabrication of various electronic devices, which require low temperature process.
8:00 PM - BM09.08.15
Skin Electronics Enabled by Intrinsically Stretchable Transistor Arrays
Sihong Wang 1 , Jie Xu 1 , Zhenan Bao 1
1 , Stanford University, Stanford, California, United States
Show AbstractHuman-oriented electronics are to be attached seamlessly both with human body for health monitoring, medication therapy, biological study, and also with human-mimetic systems such as soft robotics. Blurring their chemical and mechanical interface by using polymer materials to make electronics as soft and stretchable as skin could eliminate the discomfort/invasion during wearing, and largely enhance the information transmission with skin. Although structural engineering for rigid inorganic materials has enabled substrate-level stretchability through complicated fabrication and sacrifice in device density, utilizing all intrinsically stretchable polymer materials for electronics to achieve higher mechanical deformability and robustness, better skin compatibility, and higher device density is still at the premature stage. Recently, remarkable progresses have been made in the development of polymer semiconducting, conducting and dielectric materials possessing both high performance and intrinsic stretchability. However, the realization of functional intrinsically stretchable electronics with large number of transistors is still hindered by the lack of scalable fabrication technology to make use of these polymer materials that have completely different chemical characteristics and process compatibility than inorganic materials. Here we present the first fabrication platform for intrinsically stretchable transistor array, which has material universal applicability, ultrahigh yield and uniformity for performance. The fabricated transistor array has the mobility comparable to amorphous silicon. High stretchability of all the material components concurrently gives rise to supreme stretchability with stable performance up to 100% strain, robustness up to 1000 cycles, and an unprecedentedly high device density. Using this platform, we further build up the major circuit foundations for intrinsically stretchable skin electronics, including active matrix for functional devices arrays (e.g. as conformable and high resolution tactile sensing e-skin on human hand palm), as well as analog and digital circuit elements as the first skin-like signal processing for physiological sensors. Bridging materials to electronic development, this technological platform takes an important step forward towards the realization and wide application of intrinsically stretchable skin electronics.
8:00 PM - BM09.08.16
Long-Life Operation of Flexible Ionic Devices Using a Spray-Coated Elastomeric Encapsulation
Saeedeh Ebrahimi Takalloo 1 , Katelyn Dixon 2 , Adelyne Fannir 3 , Seyed Mirvakili 4 , Cedric Plesse 3 , Giao Nguyen 3 , Frédéric Vidal 3 , John Madden 1
1 Electrical and Computer Engineering, University of British Columbia, Vancouver, British Columbia, Canada, 2 , McMaster University, Hamilton, Ontario, Canada, 3 Laboratoire de Physicochimie des Polymères et des Interfaces, Université de Cergy-Pontoise, Cergy France, 4 , David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractHighly flexible ionic devices such as capacitive sensors with ionically conductive electrodes, electroactive polymer actuators, and batteries contain volatile solvents, mobile ions, and toxins that can undergo unwanted exchange with the surroundings. Here poly(Styrene-block-IsoButylene-block-Styrene) (SIBS)- a biocompatible elastomer- is shown to be effective at greatly reducing the loss of ions and solvent, while also allowing a high degree of deformability.
Past research focused on enhancing the lifetime of ionic devices by using hygroscopic salts such as lithium chloride or substituting wet electrolytes with ionic liquids such as 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMITFSI). These methods, although helpful in reducing or eliminating desiccation and ion exchange, are often associated with increased ionic resistance, and in general non-optimal performance of the device. SIBS is a thermoplastic elastomer with mechanical properties close to those of silicone rubber and polyurethane, previously demonstrated in implantable medical devices, and in coating of deformable electroactive polymers. Thanks to its low water absorption (20-30 µg/ cm2/ day), we are using its technical grade as an encapsulating layer for trilayer conducting polymer actuators. The rate of solvent loss and its effect on device performance are presented as functions of coating thickness.
Six samples of trilayer actuators comprising of two active layers of Poly(3,4-ethylenedioxythiophene) (PEDOT) between which an interpenetrated polymer network of Poly (ethylene oxide) (PEO) and Nitrile Butadiene Rubber (NBR) sits as the electrolyte reservoir, were prepared and soaked into a 1M solution of Li+TFSI- in PC for over a month. Spray coating of a SIBS solution (2 % in Toluene) was done to generated 45 µm and 90 µm thick coatings. The samples were then stored at 23 ± 1°C with a relative humidity of 50 ± 2 %. The mass of the samples was measured over time and compared to un-encapsulated samples.
Our results show that the un-encapsulated trilayers lose 10% of its PC content in ~5 hours – at which point their performance begins to degrade. This process slowed to be 2.5 months (~300 times slower) and 8 months (~1000 times slower) using a 45 µm and 90 mm thick SIBS coatings respectively. Bending stiffness measurements show that the device becomes ~3 times stiffer with the 90 µm thick encapsulation - mainly due to the 50 % increase in thickness, as tensile stiffness changes little. We show that encapsulation does not have a significant effect on the force generated but the active deflection decreases in inverse proportion to the encapsulation thickness, as anticipated.
Being a successful candidate to encapsulate ionic actuators, along with its high stretchability and transparency at small thicknesses (<200 µm), SIBS can also be applied to other stretchable ionic devices such as hydrogel-based transparent tactile sensors, pushing them forward towards a durable ionic skin.
8:00 PM - BM09.08.17
Controlling the Adhesion between Flexible Substrate and Carrier Wafer
Hyuk Park 1 , Seongmin Park 1 , Yoonyoung Chung 1
1 Electrical Engineering, Pohang University of Science and Technology, Pohang Korea (the Republic of)
Show AbstractIn flexible device fabrication, a rigid carrier wafer is necessary to provide a structural support and to suppress residual stress during process steps. Flexible substrate should not only be adhered onto a carrier wafer to endure the effects from fabrication process, but also be easily detached from the carrier wafer after fabrication without any performance degradation. A laser lift-off process has been employed by industry, but a cost-effective method is still needed. We applied surface treatments on a carrier wafer and found an adequate adhesion force between the flexible substrate and carrier wafer. We achieved an optimal adhesion between the two layers so that the flexible substrate can be securely mounted on a carrier wafer during fabrication and detached effectively without performance degradation.
8:00 PM - BM09.08.18
Highly Stretchable Electrospun Conducting Polymer Nanofibers
Thomas Kitto 1 , Arunprabaharan Subramanian 1 , Yang Li 1 , Zhang Shiming 1 , Fabio Cicoira 1
1 , Ecole Polytechnique de Montreal, Montreal, Quebec, Canada
Show AbstractBiomedical electronics research targets both wearable and biocompatible electronic devices easily adaptable to specific functions. To achieve such goals, stretchable organic electronic materials are some of the most intriguing candidates. Herein, we develop a highly stretchable poly-(3,4-ethylenedioxythiphene) (PEDOT) doped with tosylate (PEDOT:Tos) nanofibers. A two-step process involving electrospinning of carrier polymer (with oxidant) and vapor phase polymerization was used to produce fibers on polydimethylsiloxane (PDMS) substrate. The fibers can be stretched up to 140% of the initial length maintaining high conductivity.
8:00 PM - BM09.08.19
Strain- and Strain Rate-Invariant Conductance in a Stretchable and Compressible Conducting Polymer Foam
Yue (Jessica) Wang 1 2 , Reza Rastak 3 , Hongping Yan 4 , Feifei Lian 5 , Gan Chen 2 , Vivian Feig 2 , Eric Pop 5 , Michael Toney 4 , Christian Linder 3 , Zhenan Bao 2
1 , University of California, Merced, Merced, California, United States, 2 Chemical Engineering, Stanford University, Stanford, California, United States, 3 Civil and Environmental Engineering, Stanford University, Stanford, California, United States, 4 Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California, United States, 5 Electrical Engineering, Stanford University, Stanford, California, United States
Show AbstractAdvances in stretchable conductors have been one of the main driving forces behind the realization of wearable and epidermal electronics. However, retaining constant strain-property relationships under varying strain and strain rate remains a challenge. In this talk, we demonstrate a solution-based approach towards strain-accommodating, bio-compliant conductors. In contrast to previous stretchable conductors, this method leads to polymeric materials with conductance that has zero dependence on (1) both tensile and compressive strain over an 80% strain range, and (2) strain rate from 2.5-2560 %/min. The origin of such electro-mechanical relationship was deciphered using finite element simulation on a reconstructed model obtained with computerized tomography (CT) scans of the actual 3D structures, which allowed us to accurately account for the polydispersity of the pore sizes. In addition, these conductors are ultra-lightweight, can be molded into virtually any shape and size, and their Young’s moduli can be controllably tuned between ~4-300 kPa. Such structuring-induced mechanical properties allow the typically brittle conjugated polymers to mimic the dynamic and stiffness of biological systems, rendering this a versatile platform for designing electronic materials that can potentially form intimate interfaces with human. As a proof-of-concept, we demonstrate their use as dry EMG electrodes, which exhibited stable performance and high signal-to-noise ratio under movement at different speeds.
8:00 PM - BM09.08.20
Regulating In-Plane Wrinkling Pattern and Multi-Scale Surface Evolution with Planer Structural Confinement
Bin Xu 1 , Ding Wang 1 , Nontawit Cheewaruangroj 3 , Yifan Li 1 , Glen McHale 1 , John Biggins 3 , Yingzhu Jiang 4 , David Wood 2
1 , Northumbria University, Newcastle upon Tyne United Kingdom, 3 , University of Cambridge, Cambridge United Kingdom, 4 , Zhejiang University, Hangzhou China, 2 , Durham University, Durham United Kingdom
Show AbstractElastic instabilities, i.e. wrinkling, creasing and folding, could enable a convenient and cost effective strategy to generate surface patterns. Here, we report the experimental and theoretical studies on the formation and evolution of elastic instability morphologies on designed compliant surface. By pre-placing the structural confinements on the soft layer, the surface can be guided to form/grow instability patterns in response to the imposed constraints when being compressed, thus, yield a reliable hierarchical surface. We successfully obtain the 2D periodic wrinkle network under uniaxial compression, by using the Bravais lattice micro-patterns to regulate the strain energy distributions. At higher compression, the observed harmonic wrinkle pattern further develops into period-doubling bifurcation, then a symmetry breaking to initialise the wrinkle-creasing transition which is guided by the local curvature. By testing the theory against experiments on the designed surfaces with centred rectangular array, we show a quantitative agreement between the analytical simulation and experimental results. We also reveal a targeted formation of wrinkle-to-crease transition to yield a hierarchical surface as result of the reorganization of surface strain field. By verifying the geometrical inputs, we demonstrate control over the stepwise evolution of surface morphologies. These results have relevance to many emerging applications of morphing surfaces in wearable/flexible electronics, bio-medical systems, optical devices, etc.
8:00 PM - BM09.08.21
Thermal-Mechanical Characterization of 3D Printed Actuators Made of Shape-Memory Polymers
Connor McMahan 1 , Ethan Pickering 1 , Osama Bilal 1 , Chiara Daraio 1
1 , California Institute of Technology, Pasadena, California, United States
Show AbstractThe choice of an actuator is one of the main considerations in the development of soft robots. Since conventional electric motors cannot be used in most cases (because they are not soft), an alternative is to use bistable materials for actuation purposes. Among materials that display bistable characteristics, 3D-printed actuators made of shape-memory polymers present an additional benefit in that they can also serve structural purposes for a soft robot or conform to complex geometries. Examples of materials that meet these traits include mixtures of VeroWhite and TangoBlack polymers (referred to as digital materials). These materials are 3D-printed by Stratasys printers and can harness thermal energy from the environment to serve as actuators. In order to serve this purpose, a few preparatory steps are required. First, these materials must be brought above their glass-transition temperature. Then, they must be held in a deformed configuration while being cooled back to room temperature. This ensures that the structures are “frozen” in the deformed configuration. Finally, the polymeric structures will exert actuating forces if they are heated, and will return to the shape they were printed in so long as the external forces resisting actuation are not greater than what the polymers can exert. Because these structures can undergo large deformations and then be reconfigured to their original positions while harnessing thermal energy from the environment, they may be useful as actuators for bio-inspired mechanisms, soft robotics and autonomous structures. In order to determine the effectiveness of these shape-memory polymers as actuating materials, an apparatus and experimental method were developed to study and characterize the thermal-mechanical properties for a specific geometry. Structures of varying thicknesses were used to determine the relationship between thickness and actuation force. Performance during thermal cycling was also assessed.
8:00 PM - BM09.08.22
Design of Strained Germanium Laser Platform for On-Chip Biosensing
Buse Unlu 1 , Arman Ayan 2 , Samad Nadimi Bavil Oliaei 3 , Selcuk Yerci 2 , Cicek Boztug 1 , Ho Sun Lim 4
1 Department of Electrical and Electronics Engineering, TED University, Ankara Turkey, 2 Department of Electrical and Electronics Engineering, Middle East Technical University, Ankara Turkey, 3 Department of Mechanical Engineering, Atilim University, Ankara Turkey, 4 , Sookmyung Women's University, Seoul Korea (the Republic of)
Show AbstractThe development of lab-on-a-chip optical biosensors requires to be able to integrate light sources, sensing elements, and detectors, as well as read-out and data-processing electronics all on the same silicon (Si) substrate, which is the building block of microelectronics. Such highly integrated systems could provide unparalleled miniaturization compared to the existing hybrid solutions, and therefore be employed in presently inaccessible environments. Furthermore, if these sensors could be made flexible, they could be attached on moving organisms. However, there are two main challenges to develop such flexible lab-on-a-chip optical sensors. The main challenge is the lack of a group-IV mid-infrared (MIR) laser that could be monolithically integrated on Si due to the very low radiative efficiency of group-IV semiconductors including Si and germanium (Ge). Another challenge is to realize the flexible components comprising the sensor. Tensilely strained Ge light sources are eligible to resolve both of these issues since they can be monolithically integrated on Si chip and they are compatible with a flexible platform because strain itself is the key ingredient required to convert Ge into a group-IV material to be able to lase. We have already demonstrated that Ge can provide optical gain for biaxial strain levels larger than 1.4% and its gain coefficient can be enhanced with increasing strain [1]. At the same time, the wavelength corresponding to the peak gain coefficient of Ge can be tuned into the MIR wavelengths with increasing strain, which makes strained Ge a very promising light source to be used in a flexible lab-on-a-chip optical biosensor since most of the biological species has distinct absorption features at MIR wavelengths.
Motivated by this important role of strained Ge in the field of flexible bioelectronics, in this work we have carried out finite element method (FEM) simulations to determine the amount of the strain in novel Ge microstructures on Si. In these structures, strain is transferred from intrinsically-strained silicon nitride (Si3N4) stressor layer into suspended Ge microbridges. Both uniaxially strained and biaxially strained Ge microbridges have been designed with strain levels above the threshold for obtaining optical gain in Ge. In the simulated structures, two ends of the microbridge are embedded in the stressor layer; therefore, by tuning the intrinsic strain of the stressor layer, the strain transferred to Ge can be modified without having to reduce the microbridge width down to the nanoscale. This is a great advantage, because micro-sized width of the Ge bridge would provide strong confinement of the MIR lasing mode. Furthermore, the designed microstructure would possibly be fabricated utilizing liquid phase epitaxy. Therefore, experimental demonstration of our design would result in the first demonstration of a low-cost, CMOS-compatible strained Ge laser.
1. C. Boztug et al., Small 9, p 622-630 (2013)
Symposium Organizers
Ingrid Graz, Johannes Kepler University Linz
Anastasia Elias, University of Alberta
Ivan Minev, Technische Universität Dresden
Benjamin O'Brien, StretchSense
BM09.09: Soft Robotics
Session Chairs
Anastasia Elias
Ingrid Graz
Ivan Minev
Thursday AM, November 30, 2017
Sheraton, 2nd Floor, Republic B
8:30 AM - *BM09.09.01
Soft Sensors for Soft Robots
Rebecca Kramer-Bottiglio 1
1 , Yale University, New Haven, Connecticut, United States
Show AbstractAs advanced as modern machines are, the building blocks have changed little since the Industrial Revolution: structures, motors and gears are typically rigid, bulky and heavy. In contrast, soft robots offer the compliance and low-weight necessary to make them safe for working in close proximity to humans, as well as allowing them to squeeze into tight spaces, handle fragile objects, and be robust in collisions. The combination of elastically deformable substrates with soft sensors and actuators will allow a robot to be folded or compressed and placed into a volume much smaller than its deployed size, making transportation easier. During this talk, I will describe my group’s progress towards soft sensors using both liquid metal-based resistive sensors and conductive composite-based capacitive sensors. I will emphasize manufacturability of both sensing technologies and approaches for integration into soft robots. Finally, I will show several prototype soft-bodied systems that incorporate these sensors to achieve reliable state estimation and closed-loop control.
9:00 AM - BM09.09.02
3D Printing Optical Strain Sensors for Soft Robotics
Patricia Xu 1 , Hedan Bai 1 , Robert Shepherd 1
1 , Cornell University, Ithaca, New York, United States
Show AbstractCurrently, soft robots cannot be fully autonomously controlled because they do not have internal sensing mechanisms that give them an understanding of their current state. Since they have many degrees of freedom, a high density of internal sensors is required to control these robots. Commercially available sensors, however, would increase the stiffness of the mechanisms and interfere with the high elongations typically used in actuation. The solution to this problem has been a variety of elastomeric sensors that rely on changes in electrical signals. Stretchable electrical conductors, however, typically demonstrate inconsistent signaling during cyclic loading. As a new option for strain sensing in soft robotics, stretchable optical lightguides have been used for their low hysteresis and high sensitivity. The molding process used, however, constrains the possible placement, shapes, and density of the sensors within the actuator. In this talk, we will present 3D printing as a method to achieve more complex, higher density, internal sensor systems for improved autonomy in soft robots.
9:15 AM - BM09.09.03
Soft Material Enables Striking New Photonic and Phononic Properties
Jianfeng Zang 1 , Xin Liu 1 , Shuaifeng Li 1 , Xuefeng Zhu 1
1 , Huazhong University of Science and Technology, Wuhan China
Show AbstractSoft materials, including biological tissues, muscles, gels, and elastomers, have attracted significant attention due to their unprecedented properties on reversible and large deformation subjected to external stimuli. Together with specifically designed structures and functional components, soft material enables many new functions and properties otherwise impossible in rigid materials system. Here we demonstrate some striking examples using soft materials to generate some new functions ranging from photonics to phononics and acoustics. First, we present an experimental observation and numerical simulation of tunable topological state in soft elastic metamaterials. The on-demand reversible switch in topological phase has been achieved by changing filling ratio, tension and/or compression of the elastic metamaterials. By combining two elastic metamaterials with opposite topological invariants, we further demonstrate the formation and dynamical tunability of topological state by mechanical deformation and the arbitrary manipulation of elastic wave propagation. Second, we demonstrate a soft metasurface with out-of-plane design for tuning the energy of surface plasmon polaritons bloch wave using theory, simulation, and experiments. The resonance wavelength can be tuned in visible and near infrared range by altering the separation height. Our approach to dynamically control new phononic and photonic properties in soft materials paves the way to various systems involving large deformation and soft robotics requiring better use of energy.
9:30 AM - BM09.09.04
Developing a UV-Curable, Environmentally Benign and Degradable Elastomer for Soft Robotics
Jacob Rueben 1 , Stephanie Walker 1 , John Simonsen 1 , Yigit Menguc 1
1 , Oregon State University, Corvallis, Oregon, United States
Show AbstractThis paper outlines preliminary work in developing a safe, UV-curing, biodegradable, renewable elastomer, poly(glycerol sebacate itaconate), or PGSI, for use in soft robotics. A simple synthesis route using low-hazard and inexpensive chemical reagents was developed for easy adoption into soft robotics labs. Certain applications of soft robotics, including medical robots and agricultural sensors, involve situations in which the robot will not require retrieval after use. In these circumstances, biodegradable soft robots would be beneficial. Our previous work developed poly(glycerol sebacate) with an additive of calcium carbonate (PGS-CaCO3) for use in soft robotics, but difficult fabrication due to a lengthy thermal curing period limited the final product to polymer sheets. In order to expand into assembly of 3D structures created without additional adhesion post-cure, we incorporated a low-hazard monomer (itaconic acid) into the polymer chain to facilitate the UV crosslinking seen in other work using more hazardous acrylates. Material characterization of fresh PGSI samples gave: ultimate tensile strength ranging from 134 to 193 kPa with moduli ranging from 57 to 131 kPa and elongations at break ranging from 105 to 137 % (12 samples from 6 batches tested), and resilience values ranging from 73 to 82 % (3 samples from 3 batches tested). Fourier transform infrared spectroscopy showed a possible decrease in carbon-carbon double bonds after UV-curing, evidencing a decrease in itaconic acid methylene groups from photoinitiated free radical cross-linking. Ultimate tensile strength and elongation at break values are comparable to previously made and less safe UV-curing PGS formulations, making PGSI a possible replacement for said materials. Further PGSI characterization includes nuclear magnetic resonance spectroscopy to clarify some of the bonding and molecular structure of the PGSI chains. Simple soft robotic actuators are also assembled and characterized to establish the capabilities of PGSI as a soft robot building material.
9:45 AM - BM09.09.05
Programmed Magnetically-Triggered Ultrathin Soft Robots with Fast Actuation Speed
Xu Wang 1 , Jin Ge 1 , Gilbert Santiago Canon Bermudez 1 , Juergen Fassbender 1 , Denys Makarov 1
1 Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Saxony, Germany
Show AbstractSoft robots have been designed and developed to fulfil the demands of better deformability and adaptability to changing environment [1-2]. These soft robots could be made of various stimuli responsive materials that can be actuated by magnetic field [3], light [4], temperature [5], electric fields [6], chemicals [7], pressure [8], etc. In contrast to other actuation mechanisms, magnetic fields are appealing for numerous application scenarios (e.g. environmental, biological, medical), where the benefits stem from their long range penetration, easy accessibility and controllability [2]. There are already impressive demonstrations of magnetically triggered actuators performing as walkers, swimmers and grippers [9]. However, most of these robots are bulky (0.2 mm thick) [11], reveal low actuation speed (2.7 s deflection time) [11] and not sufficiently soft to demonstrate reversible large scale actuation amplitude (less than 1 micron) [12]. Furthermore, they require rather large magnetic fields (42 mT) [13] for actuation, which limits their application potential.
Here, we present an ultrathin and lightweight soft robot that can be actuated in a tiny magnetic field of 0.2 mT reaching full actuation amplitude with reaction times of 10 ms only. The Young’s modulus of the developed magnetic elastomer (NdFeB particles are dispersed into a PDMS host) goes down to remarkable 5 MPa while still maintaining stretchability levels of 50%. The weight of the magnetic foil is 4 mg/cm2 and it can provide 0.16 mN/mg. By programming the foils into different geometries, these soft robots are readily used for different applications, such as quick gripper that can pick, transport and release objects in a controllable manner.
[1] D. Rus et al., Nature 521, 467 (2015)
[2] M. Sitti et al., Adv. Mater. 29, 13 (2017)
[3] S. Kwon et al., Nature materials 10, 747 (2011)
[4] S.H Peng et al., J. Am. Chem. Soc. 138, 225 (2016)
[5] M. Takata et al., Nature Materials 14, 1002 (2015)
[6] J. D. W. Madden et al., Materials Today, 10, 30 (2007)
[7] J.Y. Yuan et al., Nature communications 5 (2014).
[8] G. M. Whitesides et al., Science, 337, 828 (2012)
[9] O. Sandre et al., Chem. Soc. Rev., 42, 7099 (2013).
[10] R. V. Ramanujan et al., Adv Mater., 24, 4041-54 (2012).
[11] H. Z. Liu. et al., ACS Appl. Mater. Interfaces, 8, 14182 (2016)
[12] M. Sitti et al., Nature Communications 5, 3124 (2014)
[13] D. Fragouli et al., ACS Appl. Mater. Interfaces 7, 19112 (2015).
BM09.10: 2D and 3D Printing
Session Chairs
Anastasia Elias
Ingrid Graz
Ivan Minev
Thursday PM, November 30, 2017
Sheraton, 2nd Floor, Republic B
10:30 AM - *BM09.10.01
3D Printing Hydrogel Bioelectronics and Biorobots
Xuanhe Zhao 1
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractWhile human tissues are mostly soft, wet and bioactive; machines are commonly hard, dry and biologically inert. Bridging human-machine interfaces is of imminent importance in addressing grand societal challenges in healthcare, security, sustainability and joy of living. However, designing human-machine interfaces is extremely challenging, due to the fundamentally contradictory properties of human and machine. At MIT SAMs Lab, we use nanoengineered bioactive hydrogels to bridge human-machine interfaces. On one side, bioactive hydrogels with similar physiological properties as tissues can naturally integrate with human body, playing functions such as scaffolds, catheters, drug reservoirs, and wearable devices. On the other side, the hydrogels embedded with electronic and mechanical components can control and response to external devices and signals. In the talk, I will discuss our recent works on the design and fabrication of hydrogel-based bioelectronics and biorobots and their biomedical applications. In particular, I will demonstrate a new multi-material 3D printing method to fabricate personalized and customized bioelectronics and biorobots. Based on the 3D printing method, we create i). epidermal and implantable hydrogel devices capable of sensing various physiological parameters and delivering drugs on demand and ii). hydrogel robots capable of applying pressure, manipulation and drug to delicate tissues. We will then discuss a systematic approach to design human-machine interfaces with unprecedented efficacy based on hydrogel bioelectronics and biorobots.
11:00 AM - BM09.10.02
Embedded 3D Printing of Soft Robotic Actuators with Integrated Sensors for Somatosensory Feedback
Ryan Truby 1 2 , Michael Wehner 1 2 , Robert Wood 1 2 , Jennifer Lewis 1 2
1 Paulson School of Engineering and Applied Sciences, Harvard University, Boston, Massachusetts, United States, 2 Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, Massachusetts, United States
Show AbstractEnabling closed-loop control of robotic systems comprised primarily of soft materials remains a clear challenge for the emerging field of soft robotics. Realizing true autonomy in soft robots, beyond simple open-loop control, will require integrating sensors within these soft-bodied systems to provide multiple modes of proprioceptive and exteroceptive feedback. However, at present, seamlessly embedding sensors within soft robotic actuators presents several materials- and manufacturing-related challenges. We present a method for creating soft robotic actuators innervated with multiple soft sensors that do not display hysteresis effects and demonstrate long-term reliability using multimaterial, embedded 3D (EMB3D) printing. This rapid, free-form manufacturing method enables the seamless integration of multiple materials that provide our printed actuators with the requisite mechanical properties and form to receive several modes of biomimetic, somatosensory feedback on their deformation, performance, and environmental interactions. While in this work we primarily explore one possible design for a soft robotic actuator innervated with soft sensors that could be used in autonomous soft robotic grippers, these methods and materials can be immediately extended to manufacture other soft robotic systems requiring true closed-loop control as well as form factors and architectures not readily possible with available manufacturing methods.
11:15 AM - BM09.10.03
Solution Shearing of Stretchable Polymer Semiconductor Films with Aligned Nanoconfined Morphology
Jie Xu 1 , Zhenan Bao 1
1 , Stanford University, Stanford, California, United States
Show AbstractSoft and conformable wearable electronics require stretchable semiconductors but existing ones still give relatively low initial charge-transport mobility, which give fully stretchable transistors a low performance. Films morphology strongly influences the performance of stretchable semiconducting films from both the mechanical and electrical properties. We combined the nanoconfinement effect and microstructured blade solution-shearing method to significantly improve the initial charge transport mobility, at the same time maintain the stretchability. The aligned conjugated polymer chains and high aggregations in the solution-sheared nanoconfined semiconducting films improve the intra chain and inter chain charge transportation. As a result, we have realized five stretchable semiconducting films with charge carrier mobility over 6 cm2/Vs, which are two to six times higher than the spin-coated films. The fully stretchable transistors exhibit high initial performance and high bi-axial stretchability. And we demonstrate a large area fabrication of aligned nanoconfined stretchable semiconducting films through roll-to-roll blade shearing method.
11:30 AM - BM09.10.04
3D Printed Highly Stretchable and Sensitive Tactile Sensor at Mild Conditions
Shuang-Zhuang Guo 1 , Kaiyan Qiu 1 , Fanben Meng 1 , Sung Hyun Park 1 , Michael McAlpine 1
1 , University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractThe development of methods for the direct three-dimensional (3D) printing of multi-functional stretchable electronic devices in various form factors and on a variety of surfaces could impact areas ranging from wearable electronics, energy harvesting devices, and prosthetic bionic skins, to fundamental studies on soft mechanics and human-machine interfaces. In the past decade, the development of stretchable electronic devices and sensors has dramatically accelerated, concomitant with advances in functional materials and fabrication processes. In particular, novel strategies have been developed to enable the intimate biointegration of wearable electronic devices with human skin in ways that bypass the mechanical and thermal restrictions of traditional microfabrication technologies. Here, a multi-material, multi-scale, and multi-functional 3D printing approach coupled with reverse engineering was employed to fabricate 3D tactile sensors under ambient conditions conformally onto a freeform surface. The customized sensor was demonstrated with the capabilities of detecting and differentiating human movements, including radial pulse monitoring, and finger pressing and bending. Our custom 3D printing of functional materials & devices opens new routes toward the biointegration of various sensors in wearable electronics systems, and to advanced bionic skin applications.
11:45 AM - BM09.10.05
A Direct Printing Method to Additively Pattern Silver Nanowires for Sensor and Stretchable Display Applications
Suoming Zhang 1 , Le Cai 1 , Yiheng Zhang 1 , Jinshui Miao 1 , Zhibin Yu 2 , Chuan Wang 1
1 , Michigan State University, East Lansing, Michigan, United States, 2 , Florida State University, Tallahassee, Florida, United States
Show AbstractWe have developed a direct printing process for additively patterning high aspect ratio materials -- Silver Nanowires(AgNWs) with length up to ~ 40 µm on various substrates. Well-defined and uniform AgNW features could be obtained by optimizing the printing conditions including nozzle size, ink formulation, surface energy, substrate temperature, and printing speed. Systematic characterizations were performed to investigate the electrical and electromechanical properties of the printed features with different nanowire lengths. By printing the AgNWs on a bi-axially pre-stretched PDMS substrate, we have realized a stretchable conductor that could maintain stable conductance under an areal strain of up to 156% (256% of the original area). Additionally, using the printed parallel AgNWs as electrodes, we have fabricated an ultrasensitive capacitive pressure sensor array and an stretchable electroluminescent display (stretched by 20%) on mechanically compliant substrates, implying the great potential of this unique additive patterning method in applications like E-skins and wearable electronics. Furthermore, the same strategy can be adapted to other material platforms like semiconducting nanowires, which may offer a cost-effective entry to various nanowire-based mechanically compliant sensory and optoelectronic systems.
BM09.11: Materials III
Session Chairs
Anastasia Elias
Ingrid Graz
Ivan Minev
Thursday PM, November 30, 2017
Sheraton, 2nd Floor, Republic B
1:30 PM - *BM09.11.01
High-Resolution Brain Machine Interfaces Using Flexible Silicon Electronics
Chia Han Chiang 1 , Charles Wang 1 , Sang Won 2 , Amy Osborn 3 , Bijan Pesaran 3 , John Rogers 4 , Jonathan Viventi 1
1 Department of Biomedical Engineering, Duke University, Durham, North Carolina, United States, 2 , University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 3 , New York University, New York, New York, United States, 4 , Northwestern University, Evanston, Illinois, United States
Show AbstractRight now, all of the tools that interface with our brains face a fundamental trade-off. We can either sample with low resolution, over large areas of the brain, or we can sample with fine resolution, over very small areas of the brain. This does not fit with the way our brains are structured. With more than 12 million neurons in each square centimeter of brain surface, we need to sample with high resolution over large areas in order to understand the way the brain works. The limitation is wiring. Every sensor that is currently implanted into the brain requires an individual wire to be connected to remote data acquisition systems. These individually wired, passive devices are limited to a few hundred sensors. Moving from the neuroscience equivalent of cave paintings (sensors with 10×10 pixels) to high-definition neural interfaces with hundreds of thousands of sensors will require active electrode arrays. These are systems in which the electrodes and electronics are integrated together on the same substrate. In prior work, we developed a flexible active array that allows high-resolution measurement from hundreds of electrodes with only a few external wire connections. These devices represent major advantages over current state-of-the-art technologies in that they are thin and flexible, enabling them to conform to the surface of the brain. We are now developing active electrode arrays using complementary metal-oxide-semiconductor (CMOS) technology. CMOS technology enables high-performance, large-area, active devices to be fabricated commercially at low cost. These arrays include on-board amplification, filtering and multiplexing that allows channel counts to scale to 65,536 electrodes, while simultaneously reducing noise and requiring fewer than 100 external wires. The use of high-performance CMOS electronics also allows the integration of near-field wireless technology to create fully implanted systems with no wires through the skull in the same flexible form factor.
2:00 PM - BM09.11.02
Instant Tough Bonding of Hydrogels for Soft Machines and Electronics
Daniela Wirthl 1 , Robert Pichler 1 , Michael Drack 1 , Gerald Kettlgruber 1 , Richard Moser 1 , Robert Gerstmayr 1 , Florian Hartmann 1 , Elke Bradt 1 , Rainer Kaltseis 1 , Christian Siket 1 , Stefan Schausberger 1 , Sabine Hild 1 , Siegfried Bauer 1 , Martin Kaltenbrunner 1
1 , Johannes Kepler University, Linz Austria
Show AbstractIntroducing methods for instant strong bonding between hydrogels and antagonistic materials – from soft to hard – allows us to demonstrate elastic, yet tough biomimetic devices and machines with a high level of complexity. Tough hydrogels strongly attach, within seconds, to plastics, elastomers, leather, bone and metals reaching unprecedented interfacial toughness exceeding 2000 J/m2. Healing of severed ionic hydrogel conductors becomes feasible and restores function instantly. Soft, transparent multi-layered hybrids of elastomers and ionic hydrogels endure biaxial strain with more than 2000 % increase in area, facilitating soft transducers, generators and adaptive lenses. We demonstrate soft electronic devices, from stretchable batteries, self-powered compliant circuits and autonomous electronic skin for triggered drug delivery. Our approach is applicable in rapid prototyping and in delicate environments inaccessible for extended curing and cross-linking.
2:15 PM - BM09.11.03
Self-Organized Versatile Semiconducting Interpenetrating Polymer Network for Robust Stretchable Devices
Guoyan Zhang 1 , Elsa Reichmanis 1
1 , Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractStretchable microelectronics has garnered significant attention from research and industry due to its essential role in the realization of large-area wearable, epidermal and biomedical electronic applications. Approaches for stretchable electronics have been intensively investigated: geometric structure design has been used to impart stretchability to brittle materials and intrinsically elastic electrode or semiconductor materials have been used directly as device components. Among these strategies, most efforts so far have concentrated on the design and preparation of an intrinsic elastic active layer with high charge carrier mobility. Despite significant technological advances in the realm of stretchable circuits, the development of stretchable electronics remains limited either by the elaborate synthesis process of intrinsically elastic semiconducting/conducting polymers or multi-step manufacturing processes. Thus, a simple and practical approach to stretchable devices is required.
Here, we describe a self-organized versatile conjugated polymer film through interpenetrating polymer network (IPN) formation to significantly improve mechanical ductility and optical transparency, without affecting the film electronic conductivity, even under 100% strain. The IPN formed within the semiconducting films is crucial for the obtained enhanced ductility and charge-carrier mobility. Based on this versatile semiconducting film, we explored a new practical approach to directly integrate all the stretchable components for a large area transistor array through a simple single, mechanical peel-off step and solution processing. We demonstrate robust transistor arrays exhibiting charge carrier mobilities above 1.0 cm2/Vs with excellent durability, even under 100% strain. In addition, commercial p-channel and n-channel conjugated polymers confirmed the generality of this method.
With future technological advances in the realms of wearable devices and circuits, the IPN strategy and process protocols are expected to bring stretchable electronic systems to a practical level, and represent promising directions for industry-scale roll-to-roll production of stretchable and wearable electronic devices.
2:30 PM - BM09.11.04
A Self-Healable Conducting Polymer
Zhang Shiming 1 , Yang Li 1 , Fabio Cicoira 1
1 , Ecole Polytechnique de Montreal, Montreal, Quebec, Canada
Show AbstractThe conducting polymer PEDOT:PSS has become one the most successful commercial organic conductive materials due to its high air stability, high electrical conductivity and biocompatibility. A huge amount of work has been carried out in the past two decades to investigate electronic and mechanical properties of PEDOT:PSS, but few attention was paid on its healability, i.e. the ability to repair a mechanical damage.
Here, we report, for the first time, the observation of both mechanical and electrical healability of films processed from the PEDOT:PSS suspensions. Upon reaching a certain critical thickness, the healability can be simply triggered with a droplet of water, along with an ultrafast time-resolved response of 100 ms. Significantly, after wetting the film with water, the film is transformed to a autonomic self-healing conducting polymer without the need of any external stimulation. The film maintains a conductivity as high as 600 S/cm after the addition of conductivity enhancer, with no effect on the healability. This work reveals new property of PEDOT: PSS and enables its immediate use towards flexible and biocompatible electronics, such as electronic skin, placing conducting polymers on the frontline for healing application in bioelectronics.
2:45 PM - BM09.11.05
Printable Self-Healing Graphene-Based Composites
Kirstie Ryan 1 , Steve Edmondson 1 , Brian Derby 1 , Suelen Barg 1
1 , University of Manchester, Manchester United Kingdom
Show AbstractThe ability to utilise graphene and related 2D material inks within additive manufacturing sparks a promising future for developing multi-functional composites on a commercial scale. The addition of self-healing capabilities to these materials can prolong the working lifetime, eliminating the need for further maintenance and repair. Graphene-based composites with autonomous self-healing capabilities present exciting new opportunities for sensing applications, artificial skins and soft robotics. Polyborosilxone (PBS) is a supramolecular polymer with the ability to autonomously self-heal through the spontaneous formation of dative and hydrogen bonds without the necessity of an external stimulus. The polymer is characterised as a ‘solid-liquid’ material with a shear thickening behaviour.[1][2] The viscoelastic and self-healing properties of PBS have attracted current interest into incorporating graphene into PBS matrixes to form electrically conductive smart materials with enhanced mechanical properties, for applications ranging from electrochemical sensors to responsive artificial skins.[3][4] However, at present there has been little research into using PBS or other self-healing materials for 3D fabrication processes.
In this study, we develop printable self-healing ink formulations by the design of photocurable PBS-based supramolecular networks that can incorporate graphene and other 2D materials. The inks are designed to be free-radical photocurable with the intent to be used in 3D printing techniques stereolithography SLA and direct-ink writing. Here we show that the photocurable inks can be used to 3D print self-healing graphene-based composite structures using SLA. The effects of formulations composition and processing parameters on physical properties and sensing capabilities of the materials are investigated.
References
[1] X. Li, D. Zhang, K. Xiang, and G. Huang, “Synthesis of polyborosiloxane and its reversible physical crosslinks,” RSC Adv., vol. 4, no. 62, pp. 32894–32901, 2014.
[2] B. C. K. Tee, C. Wang, R. Allen, and Z. Bao, “An electrically and mechanically self-healing composite with pressure-and flexion-sensitive properties for electronic skin applications,” Nat. Nanotechnol., vol. 7, no. 12, pp. 825–832, 2012.
[3] C. S. Boland, U. Khan, G. Ryan, S. Barwich, R. Charifou, A. Harvey, C. Backes, Z. Li, M. S. Ferreira, M. E. Mobius, R. J. Young, and J. N. Coleman, “Sensitive electromechanical sensors using viscoelastic graphene-polymer nanocomposites,” Science (80-. )., vol. 354, no. 6317, pp. 1257–1260, 2016.
[4] E. D’Elia, S. Barg, N. Ni, V. G. Rocha, and E. Saiz, “Self-Healing Graphene-Based Composites with Sensing Capabilities,” Adv. Mater., vol. 27, no. 32, pp. 4788–4794, 2015.
3:30 PM - *BM09.11.06
Ultrasoft Gel Electrodes for Micro-Volt Bio-Signal Monitoring System
Tsuyoshi Sekitani 1
1 Institute of Scientific and Industrial Research, Osaka University, Osaka Japan
Show AbstractWe have developed wireless micro-volt bio-signal monitoring system comprising ultra-soft, conductive, adhesive gel electrodes and sheet-type flexible electronic sensor systems. Ultrasoft gel electrodes consist of highly-conductive nano-conductive materials including Ag-based nanowires and flakes, carbon nanowires and nanocomposites, and bio-compatible gel composites. The conductive gel composite shows conductivity greater than 10,000 S/cm, and can be stretched more than 100% without any damages in electrical and mechanical performances, so that it can spread over arbitrary curved surfaces even on human body. With integrating the ultrafsoft gel electrodes, ultraflexible amplifier, Si-LSI platform consisting of wireless data-transmission module and analog-to-digital converter, Li-ion-based thin-film battery, and information engineering, here we would like to demonstrate the applications of multi-channel wireless sensor systems including 8-channel sheet-type electric potential monitoring systems. This wireless system with soft gel electrodes can measure biological signals less than 1 microvolt. Taking full advantages of this system, fetal electrocardiogram has been wirelessly measured.
4:00 PM - BM09.11.07
Organic and Polymer-Metal Oxide Alloy Materials for Flexible Circuits
Antonio Facchetti 1 , Binghao Wang 1
1 , Northwestern University, Evanston, Illinois, United States
Show AbstractIn this presentation we report the development of novel semiconductor and dielectric materials, as well as the process engineering, for flexible circuits. In particular we show that “ultra-soft” polymers comprising NDI units co-polymerized with “rigid” and “flexible” organic units can change how charge transport is affected by mechanical stress, demonstrating that polymer backbone composition is more important that film degree of texturing. Furthermore, we report new “soft” polymer-metal oxide alloys, where the insulating polymer can promote formation of semiconducting metal oxide amorphous phases but with improved charge carrier mobility. Again, these materials, and the corresponding electronic building blocks, can sustain far larger stresses than those based on pure metal oxide matrices. Finally, we demonstrate that these materials can enable TFT-based circuits for ultra-flexible displays and sensors on plastics.
4:15 PM - BM09.11.08
Long Side-Chain Thermoset Thiolene-Based Semicrystalline Polymer Composites for Ultra-Sensitive Temperature Sensors
Jesse Grant 1 , Kejia Yang 2 , Daphne Carrier 3 , Jonathan Reeder 4 , Walter Voit 5
1 Biomedical Engineering, University of Texas at Dallas, Richardson, Texas, United States, 2 Chemistry, University of Texas at Dallas, Richardson, Texas, United States, 3 Electrical Engineering, University of Texas at Dallas, Richardson, Texas, United States, 4 , Northwestern University, Evanston, Illinois, United States, 5 , University of Texas at Dallas, Richardson, Texas, United States
Show AbstractThe materials used in polymeric PTC (PPTC) devices are composites of polymer and conductive filler that exhibit changes of electrical resistance of several orders of magnitude, in response to a change of tens of degrees Celsius. They are commonly made of main-chain crystallizing polymers such as polyethylene and polypropylene, whose melting temperature is difficult to tune because it depends upon the length of the polymer main chains. Previous work by Yokota, et al. has improved the manufacturability and performance of PPTC devices by taking advantage of side-chain crystallinity in the scheme of acrylate polymers. It was demonstrated that the melting temperatures were tunable via modulation of the side chain length and independent of the length of the main chains. A shortcoming of the acrylate polymerization, however, is its sensitivity to oxygen, which prevents the full conversion of the reactants in atmosphere and so diminishes the performance repeatability of the derivative device.
In this presentation, we will discuss our approach to overcoming the disadvantages by implementing thiolene click chemistry, which is insensitive to oxygen, yielding more easily controllable thermal properties. In addition, whereas the making of an acrylate-based PPTC device consists of three discrete steps—the reaction, blending of filler, and screen printing—thiolene-based PPTC devices enable all three to be done simultaneously by selective photopatterning via radical-mediated step growth polymerization.
Differential scanning calorimetry (DSC), thermomechanical analysis (TMA), and out-of-plane X-ray diffraction (XRD) are carried out to characterize the melting points, thermal volume expansion, and crystal structure of the polymer composites, respectively. Temperature sensing performance of the polymer composites is demonstrated by their resistance versus temperature curves. The flexible fabricated devices possess a sensitivity of an order of magnitude change of resistance per degree Celsius at the critical temperature; therefore, the polymer composites are good candidates for the fabrication of electronic skins, which deliver diagnostic and monitoring capabilities, or alternatively imbue artificial surfaces, whether on prostheses or robots, with sensing capabilities.
Citation:
Yokota T, et al. (2015) Ultraflexible, large-area, physiological temperature sensors for multipoint measurements. PNAS 112(47): 14533-14538
4:30 PM - BM09.11.09
Novel Polymer Composite and Its Applications in Stretchable Interconenct and Capacitive Strain Sensors
Todd Houghton 1 , Jignesh Vanjaria 1 , Thomas Murphy 1 , Hongbin Yu 1
1 , Arizona State University, Tempe, Arizona, United States
Show AbstractWearable sensors, capable of detecting various motions of the human body, present unique opportunities for the development of advanced electronic interfaces. Such sensors have widespread applications in robotics, medicine, and electronic gaming. Capacitive sensors have numerous advantages. They are physically robust, can be constructed from a variety of materials in different shapes and sizes, and have the potential of be manufactured at low cost. Here, we present two a capacitive strain gauges based on a novel silver-polymer composite material. The first sensor utilized an interdigitated finger pattern, which changed capacitance during tensile strain. The silver-polymer composite was used as the conductive filler material while the commercially available silicone elastomer Ecoflex® served as both the dielectric material and substrate. The silver-polymer composite was prepared by dispersing silver flakes into a mixture of polyvinyl alcohol, poly(3,4-ethyl-ene-dioxythiophene) (PEDOT): Poly(styrene sulfonic acid) (PSS), and phosphoric acid. The second strain gauge was fashioned as a parallel plate capacitor, with the conductive silver polymer composite serving as the plates, and urethane as the dielectric material. The in-situ capacitance of the gauges was observed while the sensors were subjected to tensile and fatigue testing. The interdigitated strain gauge showed a noticeable decrease in capacitance as strain increased, a trend predicted from first principal calculations. The results of a 50 cycle fatigue test showed that the sensor underwent insignificant change in strain detection performance. The results of fatigue testing for the urethane parallel plate strain gauge showed that while the sensor initially showed promising response to strain, repeated cycling caused mechanical failure of the urethane dielectric material. From the results of our experiments, it shows that the silver polymer composite is a promising material for stretchable capacitive strain sensors but further experiments need to be carried out with alterative materials.
4:45 PM - BM09.11.10
Reel-to-Reel Fabrication of Soft Robotic Actuators Using Laser Printing and Covalent Lamination of Thermoplastic Sheets to Silicone Films
Jay Taylor 1 , Karla Perez-Toralla 1 , Ruby Aispuro 2 , Stephen Morin 1
1 , University of Nebraska-Lincoln, Lincoln, Nebraska, United States, 2 , California State University, San Bernardino, San Bernardino, California, United States
Show AbstractActuation systems that combine mechanically stiff reinforcing elements to soft elastic structures are prevalent in biology and have been critical to emerging technologies, such as soft robotics. Synthetic techniques applicable to the fabrication of such hybrid structures, especially at scale, remain challenging due to the stark contrast in both mechanical and chemical properties of the respective material types. We developed a general technique applicable to the lamination of a wide variety of commodity thermoplastic sheets onto soft silicone films through strong covalent bonds. This approach was compatible with laser printing (and other printing technologies) enabling the facile, non-lithographic patterning of the bonded regions in the laminated structures. We used this capability to design and fabricate arrays of soft actuators and functional robotic structures rapidly. This approach to soft robotic fabrication has several advantages over traditional fabrication methods: the procedure is (i) low cost and scalable to reel-to-reel processing, (ii) iterative and amicable to rapid prototyping, (iii) readily adapted to new variants of soft robotics and microfluidic technologies, and (iv) applicable to millimeter to micrometer scale soft robotics. This strategy represents a new approach to soft actuator/robot fabrication that includes a diverse set of commodity polymers and that circumvents the molding procedures typical to traditional modes of fabrication.
Symposium Organizers
Ingrid Graz, Johannes Kepler University Linz
Anastasia Elias, University of Alberta
Ivan Minev, Technische Universität Dresden
Benjamin O'Brien, StretchSense
BM09.12: Soft Materials and Mechanics
Session Chairs
Anastasia Elias
Ingrid Graz
Ivan Minev
Friday AM, December 01, 2017
Hynes, Level 2, Room 210
8:30 AM - *BM09.12.01
Kirigami Inspired-Metamaterials—From Morphable Structures to Soft Robots
Katia Bertoldi 1
1 , Harvard University, Cambridge, Massachusetts, United States
Show AbstractIn recent years kirigami has become an emergent tool to design programmable and reconfigurable mechanical metamaterials. Kirigami-inspired metamaterials allow the practitioner to exploit cuts in addition to folds to achieve large deformations and create 3D objects from a flat sheet. Therefore, kirigami principles have been exploited to design highly stretchable devices and morphable structures.
In this talk I will show that precreased folds are not necessary to form complex 3D patterns in kirigami, as mechanical instabilities in flat sheets with an embedded array of cuts can result in out-of plane deformation. Furthermore, by largely stretching the buckled perforated sheets, plastic strains develop in the ligaments. This gives rise to the formation of kirigami sheets comprising periodic distribution of cuts and permanent folds. As such, the proposed buckling-induced pop-up strategy points to a simple route for manufacturing complex morphable structures out of flat perforated sheets. Finally, I will also show that kirigami principles enable the design of morphable and transformable skins that facilitate the design of soft robots capable of locomotion.
9:00 AM - BM09.12.02
Material for Electrically-Actuated Self-Contained Soft Sensing Artificial Muscle
Aslan Miriyev 1 , Hod Lipson 1
1 Mechanical Engineering, Columbia University, New York, New York, United States
Show AbstractNatural muscle is a source of inspiration for the development of soft actuators, promising resistance to mechanical damage, contact compliance, and better compatibility for human-robot interaction. Ideally, soft actuators would also be easily fabricated and processed into a desired shape, and would produce large macroscopic strain at relatively low voltage and current, acting as an “engineering tissue”. However, most soft actuators today are based on either pneumatic or hydraulic devices, requiring external pressure supply equipment, or on dielectric elastomers, working at very high voltages (>1kV), limiting their practicality for untethered applications and complicating the miniaturization. Here we show the electrically-activated self-contained material, combining high strains of up to 900% and adequate stress of 1.3MPa with low density of 0.84g/cm3. Our soft robust material consists of silicone rubber matrix and ethanol, distributed throughout it in micro-pores. The material may be easily prepared by mixing these components at a very low cost of 3 cents per gram. We demonstrate the implementation of our material as an actuator in a variety of robotic applications, including the untethered McKibben-type soft artificial muscle, agonist-antagonist soft artificial muscle pair, soft robots and soft-hard robots, soft gripper and evolved robot with our actuator substituting an electrical motor. We enabled our artificial muscle with sensing capability, demonstrating its fully computer-controllable actuation.
9:15 AM - BM09.12.03
Understanding Solvent-Exposed poly(dimethylsiloxane) under Dynamic Loading and Exploring Energy Dissipative Damping Elements
Umut Çakmak 1 , Imre Kallai 1 , Rene Preuer 2 , Ingrid Graz 2 , Zoltan Major 1
1 Johannes Kepler University Linz, Institute of Polymer Product Engineering, Linz Austria, 2 Johannes Kepler University Linz, Soft Matter Physics, Linz Austria
Show AbstractPolydimethylsiloxane (PDMS) due to its outstanding elastic properties, reliability and easy availability is used typically for a large variety of applications such as microfluidics, sensors and optics. With the advent of stretchable electronics and soft robotics, PDMS has become the main platform, due to its adjustable mechanical properties in a wide range from hydrogel to technical elastomeric behavior. When processing PDMS for stretchable devices, the environmental conditions have a crucial impact to its life time, especially, after exposing to solvents the inherent viscoelastic behavior is altered. This is of particular interest for a product’s service time but can also offer new approaches to adjust mechanical properties. Here, we present a characterization of the most relevant material behaviors (storage modulus, loss factor, relaxation time and fatigue performance/resistance) in order to gain more insights for the durability of PDMS as well as a route to exploit this performance for damping elements.
The PDMS formulations (Sylgard 184 and Ecoflex) under investigation were exposed to four solvents (2-propanol, acetone, ethyl alcohol and water) prior to testing. Ecoflex tend to become lower modulus after solvent-exposure while the loss factor remains almost constant. On the other hand, the PDMS material’s loss factor exhibit, depending on the exposed solvent, a more differentiated characteristic. Water, ethyl alcohol and acetone reduce the loss factor more pronounced than the modulus. 2-propanol, on the contrary, leads to an opposite observation, meaning that the material is softened (lower modulus) while the loss factor is unaffected.
Additionally, we prepare samples for ball drop test and dielectric characterization to gain comprehensive understanding of the stored as well as loss behavior of the materials and to explore energy dissipative damping elements.
9:30 AM - BM09.12.04
Stretchable Printed Electronic Devices for Sensing Applications
Qingshen Jing 1 , Michael Smith 1 , Yeonsik Choi 1 , Chess Boughey 1 , Sohini Kar-Narayan 1
1 , University of Cambridge, Cambridge United Kingdom
Show AbstractFunctional materials, such as those exhibiting piezoelectricity [1] and/or triboelectricity [2] can be incorporated into soft electronic devices with applications in bio-sensing, such as pressure sensors and microfluidic lab-on-chip devices, using a state-of-the-art aerosol jet printing (AJP) technique. Printing technology enables the adoption of a variety of functional inks for fabrication of flexible and stretchable devices with simple and straight-forward steps. [3] Typically, inks containing nano or micron-sized particles are deposited onto substrates via direct writing, screen printing and/or inkjet printing. However, precise control of ink viscosity precludes application of such techniques to a wide variety of functional materials. In this respect, aerosol jet printing achieves high-resolution (~10 μm) rapid-prototyping with a large compatibility of inks and soft substrates over a considerable working area (at least 175 mm x 200 mm). [4] This technique can be used in rapid prototyping, using a variety of different inks and combinations thereof. [5] AJP allows for quick and easy customization of printing patterns, providing a practical way by which stretchable electronics can be fabricated with fine-featured patterns, which underpins development of devices with advanced functionalities.
The presentation will demonstrate the optimization of aerosol jet printed stretchable electrodes and connects using different inks including Ag nanoparticles, Ag nanowires, carbon nanotubes, conducting polymers. Particularly, electrodes and connects made of single ink formulations may suffer from fracture during stretching due to the bonding forces between the particles being mainly Van der Waals forces. To overcome this, material mixing approaches both before, during and after the printing are attempted. Mixed inks containing one/two-dimensional components may provide stronger bonding force. We demonstrate the feasibility of our technique through simple prototype bio-sensing elements that are printed and fully stretchable.
[1] Datta, A., Choi, Y. S., Chalmers, E., Ou, C., & Kar–Narayan, S. Advanced Functional Materials, 2017, 27(2).
[2] Bai, P., Zhu, G., Jing, Q., Yang, J., Chen, J., Su, Y., ... & Wang, Z. L. Advanced Functional Materials, 2017, 24(37), 5807-5813.
[3] Tan, E., Jing, Q., Smith, M., Kar–Narayan, S., & Occhipinti, L. MRS Advances, 2017, 1-9.
[4] Smith, M., Choi, Y. S., Boughey, C., & Kar–Narayan, S. Flexible and Printed Electronics, 2017, 2(1), 015004.
[5] Wang, K., Chang, Y. H., Zhang, C., & Wang, B. Carbon, 2017, 98, 397-403.
BM09.13: Applications III
Session Chairs
Anastasia Elias
Ingrid Graz
Ivan Minev
Friday PM, December 01, 2017
Hynes, Level 2, Room 210
10:30 AM - BM09.13.01
Stretchable Triboelectric Devices for on Body Gesture Sensing and Energy Scavenging
Rubaiyet Haque 1 2 , Pierre-André Farine 2 , Danick Briand 1
1 , EPFL-LMTS, Neuchâtel Switzerland, 2 , EPFL-ESPLAB, Neuchâtel Switzerland
Show AbstractWe are presenting the development of stretchable wearable triboelectric generators (TrEGs) having simple geometries. The devices are made of soft and stretchable elastomeric functional materials along with stretchable electrodes using scalable fabrication processes. The devices can be applied for sensing of and energy harvesting from human gestures, like, knee, elbow, finger joint movements.
Kinetics of human locomotion can be a promising source of renewable energy to power low power systems, and monitoring of body movements can be of interest for humans and robots. Triboelectric generator that uses the contact electrification between materials having opposite electron affinity and electrostatic induction, can be used to transform mechanical/ kinetic energy to electrical output. Compared to the previous work, we are proposing fully stretchable materials enabling the realization of soft, compliant and biocompatible generators. The latter can be cost-effectively manufactured thanks to their simple design and processing using large area fabrication.
We have evaluated the combination of different soft triboelectric materials having different charge affinity, such as polyurethane (PU), polydimethylsiloxane (PDMS), Ecoflex, Styrene ethylene butylene styrene (SEBS/dryflex). We have also implemented microstructural modifications to improve their triboelectric behavior. Stretchable electrically conductive electrodes based on carbon and silver based elastomeric composites as well as metallic nanowires were developped. Compliant triboelectric based stretchable bands combining both vertical contact separation and sliding modes mechanisms have been realized with different designs. These TrEGs were tested on body, which showed sensing and energy harvesting capabilities from human body movements.
Initial prototype consisted of electrically conductive silver-based nylon cloth laminated on film casted PDMS as outer stretchable layer, and film casted PU along with carbon based conductive elastomer layer as non-stretchable inner layer. Second generation TrEG band are fully film casted device, using carbon based stretchable elastomeric electrodes for the stretchable layer while the second layer was made of non-stretchable PU and carbon based PU electrode. Recently, we are developing third generation stretchable TrEGs using all stretchable triboelectric materials and all carbon / silver -based electrode materials, implementing large scale compatible processing methods.
We will compare the different implementations and discuss the best configurations according to the targeted body location and movement in terms of energy harvesting. Triboelectric elements positionned at different locations allows as well self-powered body movement monitoring.
10:45 AM - BM09.13.02
Ultra-Stable Biomarker Sensing Skin with Intrinsically Stretchable Ionic Polymer Matrix
Ming Liang Jin 1 2 , Sangsik Park 3 , Chi Won Ahn 1 , Do Hwan Kim 3 , Hee-Tae Jung 2
1 , Korea National Nanofab Center, Daejeon Korea (the Republic of), 2 , KAIST, Daejeon Korea (the Republic of), 3 , Soongsil Univerisity, Seoul Korea (the Republic of)
Show AbstractWearable sensing for detection of volatile organic compounds (VOCs) biomarkers from human skin can be used for early diagnosis disease and warning of potential health risks. Recently, chemiresistor sensing device has attracted intensive attention to health care monitoring due to its wearable, low cost, power efficient, rapid and highly sensitive sensing properties. Various channel sensing materials for chemiresistor have been widely developed including metal oxides, monolayer-capped metal particles, metal nanowire, conductive polymers, ionic liquids, carbon nanotubes and 2D materials. However, literally to realize the practical use of chemiresistor, channel material simultaneously with long term stability (mechanical, chemical stability), high selectivity, and high sensitivity still presents a big challenge. In this work, we explore a concept based on intrinsically stretchable ionic polymer matrix to substantially improve the sensing performance for the practical using. As a result, we show an ultra-stable (accurate Rb base line recovery, low signal noise) and highly sensitive chemiresistor wearable sensor with monitoring different VOCs biomarkers. Significantly, this sensor still has ultra-stable sensing at the robust conditions of environments (85% humidity chemical, -45oC~125oC thermal) and mechanics (1mm radius flexibility, 100% strain stretchability). In the true sense, our designed VOCs sensor have a great potential that could applied in daily health monitoring and diagnosing disease.
11:00 AM - BM09.13.03
On-Site Multiplexing of Mechanically Imperceptible Sensor Arrays
Tetiana Voitsekhivska 1 , Gilbert Santiago Canon Bermudez 1 , Ana Lebanov 1 , Anastasiia Kruv 1 , Juergen Fassbender 1 , Denys Makarov 1
1 , HZDR e.V., Dresden Germany
Show AbstractFlexible electronics is a rapidly growing research field which enables a wide range of applications, as for consumer electronics, healthcare, environmental monitoring, smart textiles, and electronic skins [1-3]. In particular, electronic skins aim to mimic or expand the human skin sensory ability, which will require the combination of distributed arrays of diverse types of sensors (i.e. temperature, tactile, strain) onto a flexible or elastomeric support [4-9]. The key challenge here is to connect each sensor in the array with the read-out electronics. For example, if 10 sensors are to be connected, one would require at least 20 wires, which would increase the overall complexity of the entire system, make it bulky and diminish its flexibility. In electrical engineering the standard approach to solve this issue is to use a multiplexing unit to minimize the amount of wires to be addressed. Yet, as there are no flexible multiplexers available, the integration of CMOS-based rigid multiplexers into flexible wearable systems is the only available solution [10]. The crucial aspect to consider is to use an extremely compact yet high performance multiplexer which improves the conformability and integration level of the system.
We have developed highly compact monolithic CMOS analog multiplexer with a die footprint of 1 mm x 4 mm which is remarkably 12 times smaller and 5 times lighter than commercially available CMOS multiplexers. This 3 x 32:1 multiplexer has also 3 times more channels, allowing addressing up to 32 sensors simultaneously using 9 wires only. Here, we applied the developed multiplexer for interfacing ultra-thin and mechanically imperceptible resistive sensor arrays realized on 6-µm-thick polymeric foils. The multiplexer was integrated on a flexible printed circuit board and coupled to the ultrathin sensors using a combination of soldering and encapsulation processes to establish reliable contacts. As a case study, we could perform real time measurements of 10 on-skin temperature sensors by placing 2 sensors on each finger of a hand. We demonstrated their ability to capture and quantify the temperature information of cold/hot objects as approached by a test subject. Although this concept was demonstrated for temperature sensors, it can be readily extended for conditioning other kind of sensors (e.g. magnetic, strain, pressure), which is promising for robotics, rehabilitation and human-machine interfaces.
[1] Y. Zhang et al., Adv. Health. Mater. 5 (2016)
[2] W. Gao et al., Nature 529 (2016)
[3] G. Schwartz et al., Nat. Comm. 4, 1859 (2013)
[4] M. Kaltenbrunner et al., Nature 499, 458 (2013)
[5] X. Wang et al., Adv. Mater. 26, 1336 (2014)
[6] M. Melzer et al., Nat. Commun. 6, 6080 (2015)
[7] M. Drack et al., Adv. Mater. 27, 34 (2015)
[8] R. Chad Webb et al., Nat. Mater. 12, 938 (2013)
[9] T. Yokota et al., PNAS 112, 14533 (2015)
[10] J. Viventi et al., Nat. Neurosc. 14, 1599 (2011)
11:15 AM - BM09.13.04
Manufacturing of Textile-Based Flexible Electrodes and Signal Traces for Wearable Applications
Vanessa Sanchez 1 2 , Oluwaseun Araromi 1 2 , Robert Wood 1 2 , Conor Walsh 1 2
1 John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 2 Wyss Institute, Harvard University, Cambridge, Massachusetts, United States
Show AbstractSmart wearable devices are growing in popularity for human-machine interfaces used in computing, augmented reality (AR) video gaming, soft robotic garments, and for biometric tracking, and require electrodes for transducers. For such devices to be adopted by users, it is necessary to retain a high degree of mechanical compliance in order to not impede a wearer’s movement and to minimize discomfort.
Flexible electrodes manufactured from deposited metals on plastic substrates are frequently used to provide electrical connections in the various aforementioned wearable applications. However, plastic deformation and cracks may propagate from repeated strains, bends, and compressive forces associated with human motion. This poor durability with respect to movement leads to incompatibilities when integrated into a garment, in addition to the material differences perceived by the wearer. The use of textile substrates can address these issues, however current textile- and thread-based electrode technologies (e.g. sewing and embroidery) have limitations in pattern complexity/resolution. Both methodologies also produce non-negligible thickness variations, which can influence system performance and user comfort.
We have developed a scalable methodology for the manufacture of robust, compliant, micro-scale, textile electrodes and signal traces for wearable transducers. Using this approach, we have demonstrated that we can consistently produce large sheets of conductive textile electrodes (20 x 50 cm) atop a textile substrate. In addition, we demonstrate conductive signal traces with minimal thickness variation (as low as 25µm), complex geometries, and feature sizes as small as 250µm; features currently not achievable by sewing and embroidery machines. The textile based electrodes and signal traces demonstrate electrical properties suitable for a wide variety of sensing applications. Finally, we demonstrate the efficacy of our method in enabling low-profile, textile-based wearable pressure sensors with excellent mechanical robustness and conformability to the wearer.
11:30 AM - BM09.13.05
Multifunctional Highly Compliant Implants for Cancer Treatment
Anastasiia Kruv 1 , Gilbert Santiago Canon Bermudez 1 , Tetiana Voitsekhivska 1 , Ana Lebanov 1 , Juergen Fassbender 1 , Tetyana Yevsa 2 , Denys Makarov 1
1 Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Dresden Germany, 2 Department of Gastroenterology, Hepatology and Endocrinology, Hanover Medical School, Hanover Germany
Show AbstractCancer is one of the main death reasons worldwide [1]. Radio- and chemotherapies, which are the most common approaches to combat this disease, cause severe side effects due to their non-selective nature [2]. As an alternative paradigm, a targeted cancer therapy has recently emerged. This method aims to affect only cancer cells thus spare the healthy tissues [3].
The large fraction of the targeted therapies rely on drug delivery by means of nanovectors (e.g. micelles, dendrimers) to the tumor site via vascular system followed by the drug release in response to local environment (e.g. pH) or binding to a certain molecule [4]. Disadvantages of those methods are a delivery complexity (e.g. due to multiple physiological barriers), non-reliability of the release mechanism, difficulty in organising the feedback for precise control over the process as well as biodegradation concerns [5, 6].
In order to overcome these limitations we propose an alternative approach to the targeted cancer treatment which relies on the implantation at the tumor site of an ultra-thin flexible device comprising a resistive heater and temperature sensor. The devices are prepared on a 6 micrometer thick PET foil. This foil thickness was found to be optimal as it provides the best compliancy to the very soft organ tissue (normal liver and cancerous livers have been used as a case study) and does not mechanically damage the liver. The heater can heat the tissue to a pre-defined temperature of up to 55 °C even when the driving current is in the range of 10 mA. The integrated temperature sensor provides a real-time feedback about the on-site thermal impact. We demonstrate a proof-of-the-concept prototype together with the evaluation of its electrical and mechanical performance and the results of the first experiments using murine models [7].
In conclusion, the presented multifunctional and highly compliant device allows in the future to realize several negative for tumor interactions including thermal destruction of the tissue [8], targeted drug release [9] and enhancement of tumor-specific immune responses [8]. In addition, it raises the possibility to establish precise control over temperature and potentially evaluate the treatment effects which are of fundamental importance for the development of the new cancer therapies, especially for such severe malignancies as liver cancer.
[1] A. Jemal et al., CA: a cancer journal for clinicians, 61(2), 69-90 (2011).
[2] Padma, V. V., An overview of targeted cancer therapy. BioMedicine, 5(4), 19-19 (2015).
[3] A. A. Alexander-Bryant et al., Advances in cancer research, 118, 1 (2012).
[4] D. Peer, R. Langer et al., Nature nanotechnology, 2(12), 751-760 (2007).
[5] A. Z. Wang et al., Annual review of medicine, 63, 185-198 (2012).
[6] M. Ferrari, Nature Reviews Cancer, 5, 161 (2005).
[7] D. Dauch et al., Nat Med 22, 744-53 (2016).
[8] K. F. Chu et al., Nature Reviews Cancer, 14, 199 (2014).
[9] M. A. Moses et al. Cancer cell, 4(5), 337-341 (2003).
11:45 AM - BM09.13.06
Bio-Inspired Bistable Shape-Changing Displacement Sensors
Hortense Le Ferrand 1 2 , Andre Studart 1 , Andres Arrieta 2
1 , ETH Zurich, Zurich Switzerland, 2 Mechanical Engineering, Purdue University, West Lafayette, Indiana, United States
Show AbstractCombining fast external actuation and sensing in shape-adaptable composites is one key element for the fabrication of smart robotic devices. However, the dynamic response of current shape-adaptable composites is quite slow and limited by their chemistry [1]. New avenues are thus needed to generate such multifunctionality and shape-adaptability in shorter time scales. To address this issue, we build bistable shells that are able to change shape in less than 200 ms upon when their curvature is decreased below a critical threshold [2]. Mechanical forces as low as 0.6 N, but also magnetic fields, are typical external triggers leading to the change in curvature. To enable magnetic actuation and electrical conductivity, we build a bio-inspired architecture spanning five levels of hierarchy. The co-orientation of hard ceramic platelets and nickel flakes (level 1) in liquid epoxy matrices is first used to anisotropically reinforce the matrix. After curing, the composite plate exhibits a remanent magnetization and electrical conductivity resulting from the percolation of the nickel flakes, while anisotropy in mechanical properties and thermal expansion are dominated by the alignment of the alumina platelets (level 2). Sequencing the process to create a bilayer structure with perpendicular directions of reinforcement (level 3) generates internal pre-stresses, leading to the formation of a curved shell. Using the appropriate geometry (level 4), as determined using finite element analysis [3], these bilayers exhibit bistability, with each stable state associated with a specific electrical conductivity. We demonstrate one potential use of such bistable shells by embedding them in a softer matrix to form a skin-like structure (level 5) where each element can be actuated independently leading to an on-off local response over a large area. The tunability of the system and the approach proposed has many promising applications for conformable soft robotic arms with simultaneous or decoupled sensing and actuation.
[1] McEvoy, M.A., Correll, N., Materials that couple sensing, actuation, computation and communication, Science, 347 (2015).
[2] Arrieta, A.F., Bilgen, O., Friswell, M.I., Hagedorn, P., Dynamic control for morphing of bi-stable composites, Journal of Intelligent Material Systems and Structures, 24 (2012).
[3] Schmied, J.U., Le Ferrand, H., Ermanni, P., Studart, A.R., Arrieta, A.F., Programmanle snapping composites with bio-inspired architecture, Bioinspiration & Biomimetics, 12 (2017).
BM09.14: Materials IV
Session Chairs
Anastasia Elias
Ingrid Graz
Ivan Minev
Friday PM, December 01, 2017
Hynes, Level 2, Room 210
1:30 PM - BM09.14.01
Intrinsically Stretchable Temperature Sensor with Robust Strain-Insensitive Performance Based on All-Carbon Stretchable Transistors
Chenxin Zhu 1 , Alex Chortos 2 , Yue (Jessica) Wang 3 , Raphael Pfattner 3 , Ting Lei 3 , Allison Hinckley 3 , Boris Murmann 1 , Zhenan Bao 3
1 Department of Electrical Engineering, Stanford University, Stanford, California, United States, 2 Department of Materials Science and Engineering, Stanford University, Stanford, California, United States, 3 Department of Chemical Engineering, Stanford University, Stanford, California, United States
Show AbstractThe development of stretchable electronics has drawn remarkable research interest to facilitate important new fields, such as electronic skins, biomedical monitoring and diagnosis, and human-machine interface. Temperature sensors are a critical component of many stretchable systems because they can provide information about metabolic activity and inflammation in biological systems and can provide valuable information about the surroundings for intelligent robotics. While several stretchable temperature sensors have been reported with good mechanical properties, devices typically suffer from cross-sensitivity with strain. In particular, a robust temperature sensor should provide an electrical output that is only determined by the absolute temperature and is insensitive to varied strains. The cross-sensitivity to strain has become one of the main bottlenecks in the application of stretchable temperature sensors.
In this work, we demonstrated an intrinsically stretchable temperature sensor with strain-insensitive performance by circuit design strategy. A stretchable thin film transistor was fabricated with all-elastomeric components. The temperature-dependent and strain-dependent performance was characterized from the single device, and a differential circuit was designed accordingly to take the advantage of temperature sensitivity and inhibit the response to strain. The designed stretchable temperature sensing circuit demonstrated a robust electrical output for indicating absolute temperature. The deviation of temperature sensing with strain was achieved an order-of-magnitude reduction by using the differential circuit approach. A representative stretchable temperature sensor shown ±1 °C deviation with up to 60 % strain within the temperature range from 17 °C to 55 °C.
Overall, we have developed a strategy that effectively suppress the cross-sensitivity from strain on temperature using a circuit architecture. This strategy of integrating intrinsically stretchable conditioning circuits with sensors could have general applicability for optimizing the output of sensors in stretchable systems. We envision that our strategy will advance the design of stretchable sensors to enable state of the art practical applications.
1:45 PM - BM09.14.02
Direct Imaging of Defect Formation in Strained Electronic Sensors and Devices by Scanning Kelvin Probe Microscopy
Tobias Cramer 1 , Beatrice Fraboni 1
1 Department of Physics and Astronomy, University of Bologna, Bologna Italy
Show AbstractReliable performance under mechanical deformation is a central goal for bioelectronics sensors and devices. The realization of mechanically rugged electronic materials and device architectures depends crucially on the understanding of how strain affects electronic material properties and leads to defect formation. Scanning Kelvin-Probe Microscopy (SKPM) is a formidable technique for nanoelectronic investigations as it combines non-invasive measurement of surface topography and surface electrical potential. Here we show that SKPM becomes feasible on free-standing, deformed flexible or stretchable samples when operated in the low-interaction regime of non-contact mode thereby providing the opportunity to study strain effects on nano-electronic properties.
As a first example we apply the technique to investigate strain effects and failure of flexible thin film transistors containing the organic semiconductor TIPS-pentacene during bending.[1] We find that the step-wise reduction of device performance at a critical bending radii is related to the formation of nano-cracks in the microcrystal morphology of the TIPS pentacene film. The cracks are easily identified due to the abrupt variation in SKPM surface potential caused by a local increase in resistance. Importantly, the strong surface adhesion of microcrystals to the elastic dielectric allows to maintain a conductive path also after fracture thus providing the opportunity to attenuate strain effects. We support our findings by numerical simulations of the bending mechanics of the hole transistor structure allowing to quantify the tensile strain exerted on the TIPS-pentacene micro-crystals as the fundamental origin of fracture.
Further we extend our studies to investigate the microscopic strain response in semiconducting polymer field effect transistors and amorphous oxide semiconductors. For each class of semiconducting material and device architecture our SKPM method allows to detail the specific failure mechanism.
[1] T. Cramer, L. Travagli, S. Lai, L. Patruno, S. De Miranda, A. Bonfiglio, P. Cosseddu, B. Fraboni, Sci. Rep. 2016, 6, 38203.
2:00 PM - BM09.14.03
A Method for Controlling Mechanical Defects, Thermo-Physical Properties and Chemical Compositions of Stretchable Bioelectronics in Industrial Process Environments
Michael Fischlschweiger 1 , Umut Çakmak 2 , Gerhard Krumpl 1 , Alexander Stock 1 , Ingrid Graz 3
1 , OTTRONIC Technology Laboratory, OTTRONIC Regeltechnik GmbH, Fohnsdorf Austria, 2 Institute of Polymer Product Engineering, Johannes Kepler Universität Linz, Linz Austria, 3 Soft Matter Physics, Johannes Kepler Universität Linz, Linz Austria
Show AbstractIn the last decade novel materials and processing technologies have been efficiently developed for stretchable electronic devices. Processing technologies and respective manufacturing conditions have a high impact on electronic device performance. Enabling mass production and commercializing of stretchable electronics with higher production safety e.g., in the field of medical applications, requires highly stable and controlled processes. In electronic industry today, 100% verification as a measure of highest quality standards is state of the art. However, for stretchable devices, besides electronic values, material and especially mechanical properties play a crucial role for the product performance. Consequently, in process control it is necessary additionally to electronic values, tracking even material properties and material defects within or at the end of production line. In this work a multi-sensor and imaging approach, based on the combination of active thermography and multispectral analysis has been developed to characterize stretchable electronic devices in industrial environment. The novel industrial characterization method combined with modern imaging strategies, based on artificial intelligence algorithms, allows to detect defects, thermo-physical material properties, molecular architectures as well as chemical compositions of the respective stretchable electronic device. Hence, the novel method can close a gap in industrial process control of stretchable bioelectronics and contribute to long-term stability and functionality.
2:15 PM - BM09.14.04
Single-Walled Carbon Nanotubes for Flexible, Stretchable and Transparent Supercapacitors
Evgenia Gilshteyn 1 , Tanja Kallio 2 , Petri Kanninen 2 , Albert Nasibulin 1
1 , Skolkovo Institute of Science and Technology, Moscow Russian Federation, 2 School of Chemical Technology, Aalto University, Espoo Finland
Show AbstractDirect integration of the CNTs produced by the aerosol methods into different applications, especially for high-performance flexible and stretchable electronics, is discussed. Produced SWCNT/polymer composite films have exhibited excellent optical and electrical properties as well as high mechanical flexibility. Wide variety of potential application of these networks has been already successfully demonstrated.
Transparent, stretchable and flexible energy storage devices have gathered great interest due to their suitability for display, sensor and photovoltaic applications. In this paper, we report the application of aerosol synthesized SWCNT thin films as electrodes for electrochemical double-layer capacitor (EDLC). SWCNT films exhibit extremely large specific capacitance (178 F g-1 or 552 µF cm-2), high optical transparency (92%) and stability for 10000 charge/discharge cycles. A transparent and flexible EDLC prototype is constructed with a polyethylene casing and a gel electrolyte.
Stretchable all-solid supercapacitors based on aerosol synthesized single-walled carbon nanotubes (SWCNTs) have been also successfully fabricated and tested. High quality SWCNT films with excellent optoelectrical and mechanical properties were used as the current collectors and active electrodes of the stretchable supercapacitors. A transmittance up to 75% was achieved for the supercapacitors made from the assembly of two PDMS/SWCNT electrodes and a gel electrolyte in between. The transparent supercapacitor has a specific capacitance of 17.5 F.g-1 and can be stretched up to 120% elongation with practically no variation in the electrochemical performance during 1000 stretching cycles.
This research was supported by the Russian Science Foundation (project No 17-19-01787).
2:30 PM - BM09.14.05
Piezo-Resistive Stretchable Sensor with Conductive Polymer-Patterned Knit Textile
Seiichi Takamatsu 1 , Toshihiro Itoh 1
1 , The University of Tokyo, Tsukuba Japan
Show AbstractWe have developed piezo-resistive stretchable sensor which is conductive polymer of poly (3, 4-ethylenedioxythiophene): polystyrenesulfonate (PEDOT:PSS) patterned knit textile for the application of human motion sensing such as virtual reality game system, and driving simulators. To monitor the motion of human fingers, hands and elbows, the sensors needs high stretchability (> 30 %) and high strain sensitivity because the skin on human joints stretches largely. Therefore conventional sensors can not detect human motion. Textile electronics, currently developed for conformable and non-invasive biomedical devices, seems to be a particularly attractive choice. Among the textiles, knit textile exhibit high stretchability due to its inherent horseshoe-shaped structure, while at the same time offers natural compatibility with a wearable format.
Therefore, we demonstrate a stretchable human motion sensors based on conducting polymer electrodes patterned on a knitted textile. We pattern electrodes made of the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and coated with polydimethylsiloxane (PDMS), and develop stretch strain sensors to detect motion of human finger joints.
The fabricated strain sensors are evaluated by stretching the textile fabric. The bending of the PET substrate produces surface strain on the PEDOT:PSS film. A electric resistance change of the PEDOT:PSS sensor is in proportion to a strain of the fabric by the piezoresistive effect. To obtain the strain from the resistance change, we need to evaluate the gauge factor of the sensors. In an experiment on gauge factor, the sensor is deformed by force gauge with linear actuators. The gauge factor found to be 6 which is three times larger than conventional copper strain gauge. Knit textile strain sensor sustains 98.1 % strain while copper strain strain sensors do less than 5 %. Finally, we developed human finger motion sensors, by placing our sensors on the glove. Our sensor exhibit high sensitivity, stretchability and high wearability which leads to highly wearable VR systems.