Andreas Offenhäusser, Forschungszentrum Juelich
Roisin Owens, University of Cambridge
Sahika Inal, King Abdullah University of Science and Technology
Christian B. Nielsen, Queen Mary University of London
BM07.01: Flexible, Stretchable Active/Passive Materials/Devices for Health Monitoring
Christian B. Nielsen
Monday PM, November 26, 2018
Sheraton, 2nd Floor, Constitution B
8:00 AM - BM07.01.01
Bioinspired Wet/Dry Adhesion for Bioelectronics
Sungkyunkwan University1Show Abstract
Recently, extraordinary performances of natural creatures living in various conditions have been explored to understand their reversible dry/wet adhesion, including gecko feet, insect secretion, mosquito needles or endoparasitic worm’s proboscis, octopus suction cups, and slug’s footpad with viscous mucus. Extensive studies on the adhesive properties of such animal skins have revealed various multiscale architectures inducing various physical interactions. The attachment phenomena of various hierarchical architectures found in nature have extensively drawn attention for developing highly biocompatible adhesive on skin or wet inner organs without any chemical glue. Structural adhesive systems have become important to address the issues of human-machine interactions by smart outer/inner organ-attachable devices for diagnosis and therapy.
Breakthroughs in flexible and conductive materials have accentuated the development of wearable or organ-attachable bioelectronics for stable biosignal monitoring and drug delivery. For such medical applications, the devices need to manifest conformal contact on human skin even under dynamic movements, as well as repeatable, long-term attachment without skin irritations or chemical contaminations. Here, we investigated an artificial reversible wet/dry adhesion systems biologically inspired by the suction cups of octopi and amphibian’s pad. Our biologically inspired architectures exhibit strong, reversible, highly repeatable adhesion to silicon wafers, glass, and rough skin surfaces under various conditions. Applying these bioinspired architectures to interfacial adhesive layers can attribute to developing skin-attachable or implantable bioelectronics for health diagnosis, controlled drug therapeutics, and achieving multifunctional integrated devices for ubiquitous-healthcare systems.
8:15 AM - BM07.01.02
Nanocellulose Printed Circuit Boards for Human Monitoring
Jonathan Yuen1,Dan Zabetakis1,Lisa Shriver-Lake1,Md Qumrul Hasan2,David Stenger1,Scott Walper1,Gymama Slaughter2
Naval Research Laboratory1,University of Maryland, Baltimore County2Show Abstract
Flexible and ultrathin substrates supporting microelectronic components have the potential to spur the development of pervasive healthcare and the internet of things by providing sensors and bioelectronics that can provide seamless and imperceptible integration. We will describe our ongoing work to develop sensing electronics on microns-thin bacterial nanocellulose for human monitoring applications. The porosity and hydrophobicity of nanocellulose sheets offer advantages that typical plastics cannot provide, such wicking of analytes and absorption of inks. We have developed a printing method to form nanocellulose printed circuit boards (PCBs), and created a simple low temperature soldering process to form circuit structures using standard surface-mount components on our nanocellulose PCBs. This has been used to create nanocellulose decals that measure human body temperature and perform pulse oximetry. We have also developed self-powered electronics for sensing of bioanalytes, such as glucose. For all applications, the fabrication processes are solution-based and requires only ambient processing, and therefore simple, potentially low-cost, and can be aimed for a wide range of applications.
8:30 AM - BM07.01.03
Intrinsically Stretchable Polymer Semiconductors and Electronics as an Emerging Platform for Bioelectronics
The University of Chicago1Show Abstract
The vast amount of biological mysteries and biomedical challenges faced by human provide a prominent drive for seamlessly merging electronics with biological living systems (e.g. human bodies) to achieve long-term stable functions. Towards this trend, the main bottlenecks are the huge mechanical mismatch between the current form of rigid electronics and the soft biological tissues.
In this talk, I will first describe a new form of electronics with skin-like softness and stretchability, which is built upon a new class of intrinsically stretchable polymer materials and a new set of fabrication technology. As the core material basis, intrinsically stretchable polymer semiconductors have been developed through the physical engineering of polymer chain dynamics and crystallization based on the nanoconfinement effect. This fundamentally-new and universally-applicable methodology enables conjugated polymers to possess both high electrical-performance and extraordinary stretchability. Then, proceeding towards building electronics with this new class of polymer materials, the first polymer-applicable fabrication platform has been designed for large-scale intrinsically stretchable transistor arrays. As a whole, these renovations in the material basis and technology foundation have led to the realization of circuit-level functionalities for the processing of biological signals, with unprecedented mechanical deformability and skin conformability. Equipping electronics with human-compatible form-factors has opened a new paradigm for wearable and implantable bio-electronic tools for biological studies, personal healthcare, medical diagnosis and therapeutics.
 J. Xu#, S. Wang# …… Z. Bao Science 355, 59-64 (2017).
 S. Wang#, J. Xu# …… Z. Bao Nature 555, 83-88 (2018).
 S. Wang#, J. Y. Oh#, J. Xu#, H. Tran, Z. Bao Accounts of Chemical Research 51, 1033–1045 (2018).
8:45 AM - *BM07.01.04
Human Inspired Bio-Electronic Sensor Skins
National University of Singapore1,Agency for Science Technology and Research Singapore2Show Abstract
Human sensory organs such as the skin have evolved to have excellent sensing performance and ultra-robustness. Electronic versions of skin have witnessed tremendous interest and development over the last decade1. Functional soft, flexible and stretchable materials are crucial to the continued evolution of skin-like sensor applications in emerging robotic systems2, new human-machine interfaces and life-like prosthetics3.
Here, I will discuss our recent work in next generation technologies for bio-electronic skins using an integrated hybrid materials approach that synergizes the best qualities of organic and inorganic materials. For example, recent developments in self-healing polymeric systems have propelled the exciting notion that electronic systems can repair themselves when damaged4. Bio-inspired digitization of analog signals have also enabled us to develop artificial mechano-receptors that optically interfaces with neurons5. These sensor and materials technologies would be extremely applicable in an increasingly advanced cybernetic and Artificial Intelligence (AI) robotics future.
1. Hammock, M. L., Chortos, A., Tee, B. C. K., Tok, J. B. H. & Bao, Z. 25th anniversary article: The evolution of electronic skin (E-Skin): A brief history, design considerations, and recent progress. Adv. Mater. 25, 5997–6038 (2013).
2. Larson, C. et al. Highly stretchable electroluminescent skin for optical signaling and tactile sensing. Science 351, 1071–4 (2016).
3. Lipomi, D. J. et al. Skin-like pressure and strain sensors based on transparent elastic films of carbon nanotubes. Adv. Mater. 23, 1771–1775 (2012).
4. Tan, Y. J., Wu, J., Li, H. & Tee, B. C. K. Self-Healing Electronic Materials for a Smart and Sustainable Future. ACS Appl. Mater. Interfaces 10, 15331–15345 (2018).
5. Tee, B. C. K. et al. A skin-inspired organic digital mechanoreceptor. Science (80-. ). 350, 313–316 (2015).
9:15 AM - BM07.01.05
Fully Printed All-Polymer Tattoo/Textile Electronics for Electromyography
Eloise Bihar1,Timothee Roberts2,Jozina De Graaf2,Mohamed Saadaoui3,Esma Ismailova3,George Malliaras4,Khaled Salama1,Sahika Inal1
King Abdullah University of Science and Technology1, Aix Marseille Universite2,Ecole des Mines de Saint Etienne3,University of Cambridge4Show Abstract
Driven by the ever-growing needs for developing portable, easy-to-use, noninvasive diagnostic tools, biomedical sensors that can be integrated on textiles or even directly on human skin have come to fruition. Wearable sensor technologies that seamlessly interface electronics with human skin can be especially promising for detecting a wealth of biologically relevant signals ranging from neuro-muscular activity, to electrophysiology, even to metabolite profiles.
In this work, we present a simple and low cost platform fabricated on a tattoo paper used for on-skin electromyography (EMG) measurements. The electrodes comprising the conducting polymer poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS) are directly inkjet-printed on the tattoo paper. Addressing the integration challenge common for stretchable electronic devices, we connect the tattoo electrodes to the acquisition system through a textile in the form of a wristband comprising of printed PEDOT:PSS contacts. While the textile wristband conforms around the “tattooed” skin, it enables a reliable contact with the electrodes beneath due to its conformability around the limb. We show that this tattoo/textile electronics system, which does not rely on gels or expensive metallic materials, is able to detect the biceps activity of the arm during muscle contraction for a period of seven hours, with comparable performance to conventional wet biopotential electrodes. Combining the tattoo electronics with the electronic textile allows for facile integration of skin-like electrodes with external electronics.
9:30 AM - BM07.01.06
Fabrication of Fabric Biomedical Electrode Array with Printable Electronic Ink and Hot-Melt Film for Electromyography
Seiichi Takamatsu1,Toshihiro Itoh1
The University of Tokyo1Show Abstract
We have developed fabric biomedical electrode array where silver paste, conductive polymer and ionic liquid gel are printed and insulation layers are formed with hot melt film on the fabric substrate.
Recently, wearable electronic devices such as Microsoft Hololens, google glass, sportsband, or other tools have been developed and commercialized for human healthcare monitoring and information tools. Among wearable electronic devices, wearable ECG or EMG electrodes are promising for human motion sensing tools. Especially for monitoring human hand or foot motion sensing, the biomedical electrode array which is made of fabric is necessary.
To make biomedical electrodes array, new fabrication process of fabric multilayer electrodes which consists of biomedical electrode parts to contact human skin and the wiring parts from biomedical electrodes parts to the amplifiers are required. Previous study (S. Takamatsu,et.al., "Direct patterning of organic conductors on knitted textiles for long-term electrocardiography," Scientific Reports, vol. 5, 15003(7pp), Oct 2015.) reports single layer fabric electrodes, but the multilayer electrodes has not been fabricated on the fabric and the biomedical electrode array has not been achieved. The most difficult fabrication process to make multilayer electrodes is to construct insulation layer between multiple electrode because most of the insulation inks are dissolved by the solvent of second layer electrode ink(i.e., toluene), or dissolve the first layer electrode with the solvent of the insulation ink. Our new fabrication process of fabric multilayers consists of the electronic ink printing and hot-melt film sticking on the fabric. Laser cut hot melt film is placed on the electrode printed film and heated to stick to the film as insulation layer. Hot melt film has the advantages in which the hot melt film is not dissolved in the solvent of inks and can combine several layers of functional fabric and films.
The developed fabrication process of fabric biomedical electrode array with printable electronic ink and hot-melt film for Electromyography is following steps. 1. Silver paste wiring electrode is printed on the stretchable polyurethane film. 2. Laser cut hot melt film is placed on the electrode and heated. 3. The patterned urethane film is attached on the knit fabric with hot melt film. 4. Conductive polymer of PEDOT PSS and ionic liquid gel is patterned on another knit fabric for making biomedical electrode part. 5. Wiring part fabric and biomedical electrode fabric are attached by hot melt film and glue. By using our process, the 2x5 array biomedical electrode which has 1cm2 biomedical electrodes parts and 0.5 mm wide wiring can be successfully fabricated. The impedance between electrodes and human skin is less than 1 MOhm, which is useful for EMG monitoring. Thus, our process will useful for wearable multi array of EMG measurement.
9:45 AM - BM07.01.07
Sub-300 nm Thin-Film Au/Parylene Dry Electrodes for Motion Artifact-Less sEMG and sECG Monitoring
Robert Nawrocki1,2,3,Hanbit Jin1,Sunghoon Lee1,Tomoyuki Yokota1,Masaki Sekino1,Takao Someya1,4
Univ of Tokyo1,Purdue University2,Birck Nanotechnology Center3,Thin-Film Device Laboratory & Center for Emergent Matter Science (CEMS)4Show Abstract
Accurate, imperceptible and long-term monitoring of vital biopotential signals promises to revolutionize healthcare industry by shifting from costly and uncomfortable hospital visits to in-home usage. Currently available wearable electronics are typically rigid with non-conformal skin contact resulting in poor data quality, necessitating the integration of such bioelectronics  directly onto the skin . Increasing the conformity of the artificial electronic skin to the soft, irregular and stretchable human skin typically results in improved signal quality and user comfort .
We report on the fabrication of self-adhesive and conformable to highly irregular three-dimensional soft surfaces, sub-300 nm thin dry electrodes that produce biopotential (sEMG and sECG) recordings of excellent quality (SNR). The electrodes are based on thermally evaporated thin film (100 nm) of Au, sandwiched between two layers (100 nm each) of CVD-deposited biocompatible parylene (parylene/Au/parylene). They are fabricated on glass substrates, with fluorinated polymer (85 nm) and poly(vinyl alcohol) (PVA, 5 µm) sacrificial layers used for delamination and ease of handling. Parylene is etched away at the skin-interface side, allowing for direct Au contact with the skin. Following delamination, electrodes are placed on pre-stretched human skin and sprayed with H2O to remove PVA, forming a skin/Au/parylene structure. The skin is then dried and relaxed, with the ultra-thin film conforming to the skin groves via wan der Waals forces , without any additional adhesives.
These simple-to-fabricate and use, ultra-thin sensors show single-day electrical and mechanical stability of up to ten hours. Their bending stiffness was calculated to be comparable to stratum corneum, the uppermost layer of human skin, at ~0.33 pNm2, which is over two orders of magnitude lower than the bending stiffness of a 3.0 µm thin sensor. Compared with the thicker sensor, its impedance also decreased by almost two orders of magnitude. Laminated on a pre-stretched elastomer, the sensor forms wrinkles with a period of 17 µm and amplitude of 4 µm, agreeing with theoretical calculations.
In contrast to wet adhesive Ag/AgCl electrode, with skin vibrations of up to ~15 µm, the sensor demonstrates motion artifact-less sEMG monitoring. Additional impedance and sEMG measurements reveal that the decrease of impedance, as well as the motion artifact-less operation, is likely due to improved skin adhesion of the sub-300 nm thin sensor.
With compatible fabrication to our previously demonstrated sub-300 nm thin electronics , this demonstrates a path for integration of skin-laminated systems consisting of sensors and electronics.
 M. Irimia-Vladu, et al., Adv. Fun. Mat. 20, 4069-4076 (2010)
 T. Yokota, et al., Science Adv. 2, e1501856 (2016)
 D.H Kim, et al., Nature Mat. 9, 511-517 (2010)
 M. Fernandez, et al., Biomed Inst. Tech. 34, 125 (2000)
 R. Nawrocki, et al., Adv. Ele. Mat. 2, 4 (2016)
10:30 AM - BM07.01.08
Multifunctional Silk Adhesive for Epidermal Electronics
Hyojung Kim1,Ji-Won Seo1,Hyunjoo Lee1
Korea Advanced Institute of Science and Technology1Show Abstract
In order to improve the signal accuracy and long-term monitoring of electronics on biological skin, it is essential to achieve a conformal and robustly adhered electronics/biological skin interface. Here, we suggest a biocompatible calcium (Ca)-modified silk adhesive for robust epidermal electronics on biological skin. At optimized weight ratio of silk:Ca2+ of 70:30, the silk adhesive shows strong adhesion force (> 600 N/m) through enhanced mechanical interlocking at interface. The physical mechanism facilitates a high adhesion on various substrates and a reusability of silk adhesive. Moreover, a water-degradability of silk adhesive shows the easy detachment without any high external force. With the multifunctional characteristics such as reusability, biocompatibility, and water-degradability, we fabricate the practical epidermal electronics: strain sensor, touch sensor, and long-term drug delivery system to demonstrate the potential of the proposed silk adhesive.
10:45 AM - BM07.01.09
Deformable Electronic Materials for Two-Way Communication with Biological Systems
University of California, San Diego1Show Abstract
The goal of this project is to create a class of electronic materials that can measure signals and interface with the nervous system for two-way communication with biological systems. The project is exploring two classes of materials. (1) Metallic nanoislands on single-layer graphene for cellular electrophysiology and wearable sensors. We have used these materials to measure the forces produced by the contractions of cardiomyocytes using a piezoresistive mechanism. Separately, we have developed orthogonal methods of stimulating myoblast cells electrically while measuring the contractions optically (a modality we nicknamed as “piezoplasmonic”). We have also used these sensors to measure the swallowing activity of head-and-neck cancer patients who have received radiation therapy and are at risk of dysphagia arising from fibrosis of the swallowing muscles. The combination of strain sensing, surface electromyography, and machine learning can be used to measure the degree of dysphagia. (2) We have developed ionically conductive organogels for haptic feedback. Medical haptic technology has myriad potential applications, from robotic surgery and surgical training, to tactile therapy for premature infants and patients with neurological impairment.
11:00 AM - *BM07.01.10
Ultrasoft, Bio-Compatible Electronic Systems for NeuroScience
Osaka University1Show Abstract
We present an implantable sheet-type flexible electronic sensor system for long-term simultaneous monitoring of an electrocorticogram (ECoG) from the brain surface and local field potential (LFP) from the deep brain. Ultrasoft gel electrodes provide a minimally invasive interface consisting of highly conductive nano-conductive materials including Ag-based nanowires, thermoplastic polymers, and bio-compatible gels. The gel composite shows conductivity greater than 10,000 S/cm and can be stretched more than 100% without any reduction to its electrical and mechanical performance. Hence, it can be stretched across arbitrarily curved surfaces, including the ultrasoft brain surface.
By integrating ultrafsoft gel electrodes, an ultraflexible amplifier, and a wireless Si-LSI platform with a thin-film battery, we intend to demonstrate the applications of long-term implantable wireless sheet sensors, including 64-channel sheet-type electric potential monitoring systems. This wireless system with soft gel electrodes can measure biological signals of less than 1 μV. Taking full advantage of this system, simultaneous signals from the cerebral cortex in the ECoG and LFP have been wirelessly measured in animal experiments including non-human primates for over a month. Long-term biocompatibility, electrical performance, and mechanical stretchability and durability are discussed for the integration of nanomaterials and processes and wireless low-noise sheet-type systems.
This research is partially supported by the Brain Mapping by Integrated Neurotechnologies for Disease Studies (Brain/MINDS) from Japan Agency for Medical Research and development, AMED.
11:30 AM - BM07.01.11
Flexible Biosensors for Non-Invasive Medical Diagnostics
Agostino Romeo1,Paul Eduardo David Soto Rodriguez1,Ana Moya2,3,Gemma Gabriel2,3,Rosa Villa2,3,Rafael Artuch4,5,Samuel Sanchez1,6
Institute of Bioengineering of Catalonia1,National Centre of Microelectronics - Microelectronics Institute of Barcelona2,Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN)3,Hospital Sant Joan de Déu4,CIBER-ER (Biomedical Network Research Center for Rare Diseases), Instituto de Salud Carlos III5,Institucio Catalana de Recerca i Estudis Avancats (ICREA)6Show Abstract
In the last few decades the quality of life has significantly improved due to the achievements of biomedical technology. Innovative healthcare solutions contributed to these advances by decreasing costs and making health assessment easier and more accessible. Versatile biochemical sensors targeted to health biomarkers and bioanalytes (metal ions, proteins, amino acids, glucose, lactate, etc.) can non-invasively monitor the health status of the user by analyzing external body fluids (sweat, saliva, tear fluid) alternative to blood.[1,2] On-demand biosensing is envisaged due to the versatility of sensing platforms that can adapt to specific needs in terms of target biomarkers and health issues to monitor. To this regard, several recognition systems, including antibodies, enzymes, and inorganic nanomaterials can be used to modify the sensors to achieve high selectivity towards target analytes. In this scenario, recent advances in microfabrication, sensor technologies and data transmission led to the developments of point-of-care (PoC) diagnostics.
Here we present few examples of biosensors for painless and on-demand self-assessment of health conditions. In particular, we describe a non-invasive electrochemical sensor for the non-enzymatic analysis of tear glucose. Electrochemical sensing is chosen among other types of transduction because it is well suited for simple, rapid, and cost-effective personalized medicine devices. Electrodes are fabricated on soft and flexible materials using inkjet printing and then modified with CuO microparticles (CuO-µPs) to carry out non-enzymatic detection of glucose. This detection mechanism is based on the CuO-catalyzed electro-oxidation of glucose in alkaline environment, due to the electrochemical conversion of CuO into strong oxidizing Cu(III) species such as CuOOH or Cu(OH)4−. Glucose detection is achieved by CA, with an excellent linearity observed in the 3–700 µM range, matching typical glucose levels in tears. A sensitivity of 850 µA mM−1cm−2 and a limit of detection (LOD) of 2.99 µM are calculated. This sensor shows good selectivity, reproducibility, and life-time, resulting in a reliable tool for painless and non-invasive self-assessment of diabetes, as confirmed by tests on tear samples.
Personalized and non-invasive sensing technologies allow to easily and frequently monitor the health status of an individual as often as needed. This helps make early-stage detection simpler and more convenient, thus enhancing the efficacy of therapeutic treatments. Rapid and cheap PoC diagnostics also allows improving the life style of patients, by interfering in low or negligible extent to their daily activities.
 A. Romeo, et al. Lab Chip 16, 1957 (2016)
 D. Vilela, et al. Lab Chip 16, 402 (2016)
 A. Romeo, et al., Appl. Mat. Today 10, 133 (2018)
11:45 AM - BM07.01.12
Highly Durable, Ultrasensitive Nanoscale Crack Based Mechano-Sensor for Bio-Signal Monitoring Inspired by Spider’s Sensory Organs
Byeonghak Park1,Daeshik Kang2,Tae-il Kim1
Sungkyunkwan Univ1,Ajou University2Show Abstract
With increasing demand for the detection of delicate bio-signals for medical electronics, the Internet of Things (IoT), E-skin and flexible integrated circuit (IC) devices, an enhancement in sensitivity has become a major issue in flexible mechanosensors, however, overcoming the limited sensitivity remains problematic. Here, we introduce mechanosensors inspired by spiders having an ulltrasensitivity, durability. For ultrasensitivity and durability, we considered the geometrical effects in cracks and self-healable polymers. By controlling crack depth by simple propagating process, the sensitivity of our sensor shows ~15,000 in 2% strain, which is the world best sensitivity value. Due to the high sensitivity, the signal-to-noise-ratio is 6 times higher than before, up to ~35 so that it can be used in sensing human voice clearly. Also, self-healable polymer helps to recover the crack gaps after 25,000 cycles. We introduce the possilibility of semi-permanent uses over 1,000,000 cycles in our sensors. The spider inspired sensory system with high sensitivity and durability would provide versatile novel applications such as E-skins, devices for medical applications, and IoT applications etc.
BM07.02/EP05.02: Joint Session: Bioelectronic Active Materials
Monday PM, November 26, 2018
Sheraton, 2nd Floor, Constitution B
1:30 PM - *BM07.02.01/EP05.02.01
Interacting Ion and Electron Currents
Swansea University1Show Abstract
Ionic and electronic conduction mechanisms are underpinned by fundamentally different physics . For example, ions diffuse through a conducting matrix via centre of mass transport that can be described by classical processes. Electrons and holes are quantum mechanical entities characterised by delocalisation, tunnelling or hopping. These fundamental differences impose radically different length-and-time-scales on ionic and electronic conduction – and generally speaking the solid-state physics of ions and electrons have remained two very different fields requiring different skill sets . However, bioelectronics, where a central challenge is the transduction between ion and electron currents, is a scientific collision point between the two worlds.
In my talk I will summarise the major differences between ionic and electronic solid state electrical conduction. I will also describe methods that can probe the relevant time-and-length scales in order to identify and disentangle the native signatures of each carrier type [3, 4]. A number of model systems and devices will be exemplified that allow the study of ion and electron conduction processes, and indeed provide a means to test prototypical concepts in transduction and bioelectronic logic interfaces [5, 6].
 N. Amdursky, E. Glowacki & P. Meredith, Advanced Materials, 2018, (in press)
 P. Meredith, C. J. Bettinger, M. Irimia-Vladu, A. B. Mostert and P. E. Schwenn, Reports on Progress in Physics, 2013, 76, 034501
 A. B. Mostert, B. J. Powell, F. L. Pratt, G. R. Hanson, T. Sarna, I. R. Gentle and P. Meredith, Proceedings of the National Academy USA, 2012, 109, 8943-8947
 A.B. Mostert, S.B. Rienecker, C. Noble, G.R. Hanson & P. Meredith, Science Advances, 2018, 4(3), eaaq1293
 M. Sheliakina, A.B. Mostert & P. Meredith, Materials Horizons, 2018, 5, 256-263
 D.J. Carrad, A.B. Mostert, A.R. Ullah, A.M. Burke, H.J. Joyce, H.H. Tan, C. Jagadish, P. Krogstrup, J. Nygard, P. Meredith & A.P. Micolich, Nanoletters, 2017, 17(2), 827-833
2:00 PM - BM07.02.02/EP05.02.02
The Device Physics of Organic Electrolytic Photocapacitors—From the Nanoscale to the Single Cell Level
Vedran Derek1,Marie Jakesova1,Tobias Cramer2,Marek Havlicek3,David Rand4,Yael Hanein4,Daniel Simon1,Magnus Berggren1,Fredrik Elinder1,Eric Glowacki1
Linkoping University1,Università di Bologna2,Czech Metrology Institute3,Tel Aviv University4Show Abstract
We have recently developed the organic electrolytic photocapacitor (OEPC), a nanoscale optoelectronic device for eliciting action potentials in neurons. Herein, we cover in detail the physical mechanisms behind the charge generation and dynamics of charging and capacitive coupling in these devices using optoelectronic/electrochemical measurements combined with simulation and modeling. Electrochemical impedance measurements allow corroboration of these models, and reveal the nature of photocapacitive and photofaradaic effects in the devices. Using scanning probe microscopy techniques, we have evaluated the mechanical properties of the nanocrystalline films, finding relatively low Young’s moduli in the range of 500 MPa. In order to take a reductive approach compared with previous measurements of neurons and electrogenic tissues, we have validated the performance of OEPCs using nonexcitable cells, xenopus laevis oocytes. We find rapid membrane potential changes in the range of tens to hundreds of millivolts are induced by OEPC devices, showing extremely effective capacitve coupling and explaining previous findings of action potential generation. The overall result of our work is a fuller physical and mechanistic understanding of this novel device platform, and a roadmap for guiding future development.
2:15 PM - BM07.02.03/EP05.02.03
The Design of Air Stable, Redox Active Conjugated Polymers and Their Applications in Accumulation Mode OECTs
Alexander Giovannitti1,Reem Rashid2,Jenny Nelson1,Iain McCulloch1,Jonathan Rivnay2
Imperial College London1,Northwestern University2Show Abstract
Organic electrochemical transistors (OECTs) are receiving a great deal of attention due to the ability to efficiently transduce biological signals. The working principle of OECTs relies on the modulation of the conductivity of an organic semiconductor, which can be modified by applying a potential at the gate electrode and driving electrochemical redox reactions in aqueous solution (doping/de-doping of the organic semiconductor). OECTs can either be operated in accumulation1–3 or depletion mode4 where the operation in accumulation mode has the advantage of lowering the operational voltage and therefore improve the power consumption of the device (device is in an off state rather than an on state when no gate voltage is applied). Recently, high performing OECT materials have been reported based on electron rich alkoxybithiophene copolymers which show low oxidation potentials in aqueous electrolytes and enable OECT operation at low voltages. 2
However, one drawback of these easily oxidizable polymers is that the copolymers can become oxidized by reactions with oxygen from ambient air. This result in the formation of p-doped polymers and superoxide anions (O2-) where the latter is a reactive radical and might cause harm to biological systems or degrade the organic semiconductor. As a result of this oxidation reaction, a constant gate voltage would need to be applied to keep the material in its neutral state (and the device off).
We will present the development of an air-stable conjugated polymers based on donor-acceptor type copolymer. The copolymer shows reversible redox reaction at potentials below 0.3 V vs Ag/AgCl. When exposed to aqueous ambient conditions, the polymer does not become oxidized. Long-term stability tests were carried out where devices were exposed to ambient conditions for more than 6 months with no sign of degradation. The polymer shows a good stability when charged with up to one hole per repeat unit (polaron) with transconductances in the range of 80 S/cm (at -0.7 V). This work demonstrate the importance of chemical design strategies for the development of accumulation mode OECT materials to mitigate reactions with oxygen in aqueous electrolytes and ambient conditions.
1. Inal, S. et al. Adv. Mater. 26, 7450–7455 (2014).
2. Giovannitti, A. et al. Proc. Natl. Acad. Sci. 113, 12017–12022 (2016).
3. Nielsen, C. B. et al. . J. Am. Chem. Soc. 138, 10252–10259 (2016).
4. Khodagholy, D. et al. Nat. Commun. 4, 2133 (2013).
2:30 PM - *BM07.02.04/EP05.02.04
Polythiophene Derivatives as Mixed Organic Ionic and Electronic Conductors
University of Washington1Show Abstract
Mixed organic ionic and electronic conductors are being explored for a wide range of applications, from bioelectronics to neuromorphic computing, artificial muscles and energy storage applications. These materials exploit the simultaneous transport properties of ionic and electronic carriers to enable novel device functions. Recently, polymer semiconductors have received significant amounts of attention because of their flexibility, biological compatibility and ease of fabrication. These materials, particularly thiophene-based polymers such as poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS) and related derivatives, have demonstrated significant enhancements in performance in a relatively short amount of time, with transconductance values of PEDOT:PSS transistors surpassing those achieved even with graphene.
Through our NSF Designing Materials to Revolutionize and Engineer our Future (DMREF) award with researchers at Cornell University and the University of Chicago, we have been investigating the synthesis of ethylene-glycol functionalized polythiophenes, their thin film morphology, and their ionic and electronic conductivities, and comparing against theoretical predictions. In this talk, the effect on the density of the ethylene-glycol side chains and their pattern of placement on ionic conductivity will be discussed.
3:00 PM - BM07.02/EP05.02
3:30 PM - *BM07.02.05/EP05.02.05
Mixed Conductivity in Conducting Polymer Thin Films
University of Stuttgart1Show Abstract
This talk will give an overview about our recent activities on electronic and ionic conductivity in conjugated and redox polymer thin films with different molecular architectures. Preparation of films is done either by electropolymerization or solution deposition followed by morphology tuning, e.g. by solvent vapor annealing.
We are particularly interested in three-dimensional architectures based on branched monomers such as terthiophenes (3T) or triphenylamines (TPA). TPA redox moieties are useful to allow for electrochemical or chemical crosslinking of as-deposited films. Both, with TPA redox polymers and with polymers which bear TPA as pending redox moieties of linear polythiophenes we could perform successful crosslinking and simultaneous doping of polymer films. The films provide very high stabilities with high electronic conductivities as evidenced by cyclic voltammetry coupled with in-situ conductance measurements and four-point-probe measurements. In the case of 3T we have reported on homopolymer and copolymer films of 3T and ethylenedioxythiophene which allow polymer-analogous reactions to induce ionic functionalities, thereby creating branched conjugated polyelectrolyte films., 
To get a better understanding on mixed conductivity in polymer films, we have recently performed a study on electronic and ionic conductivity of linear conjugated polyelectrolytes by impedance spectroscopy and dc-measurements. The clear dependence of the conductivities as function of humidity and degree of doping will be discussed in the talk in more detail.
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 M. Goll, A. Ruff, E. Muks, F. Goerigk, B. Omiecienski, I. Ruff, R.C. González-Cano, J.T. Lopez Navarrete, M.C. Ruiz Delgado, S. Ludwigs, Beilstein J. Org. Chem. 11, 2015, 335.
 T.V. Richter, C. Bühler, S. Ludwigs, J. Am. Chem. Soc. 134, 2012, 43.
 R. Merkle, P. Gutbrod, P. Reinold, M. Katzmaier, R. Tkachov, J. Maier, S. Ludwigs, Polymer 132, 2017, 216.
4:00 PM - *BM07.02.06/EP05.02.06
Glycolated Thiophene Oligomers and Polymers for Bioelectronic Applications
NIL Technology ApS1Show Abstract
4:30 PM - BM07.02.07/EP05.02.07
Organic Electronics for Neuromorphic Computing
Yoeri van de Burgt1
Eindhoven University of Technology1Show Abstract
Neuromorphic computing could address the inherent limitations of conventional silicon technology in dedicated machine learning applications. Recent work on silicon-based asynchronous spiking neural networks and large crossbar-arrays of two-terminal memristive devices has led to the development of promising neuromorphic systems. However, delivering a parallel computation technology, capable of implementing compact and efficient artificial neural networks in hardware, remains a significant challenge. Organic electronic materials offer an attractive alternative to such systems and could provide neuromorphic devices with low-energy switching and excellent tunability, while being biocompatible and relatively inexpensive.
This talk describes state-of-the-art organic neuromorphic devices and provides an overview of the current challenges in the field and attempts to address them1. We demonstrate a novel concept based on an organic electrochemical transistor2 and show how some challenges in the field such as stability, linearity and state retention can be overcome3.
Furthermore, we investigate chemical doping mechanisms in the active material for improved material functionality and demonstrate that this device can be entirely fabricated on flexible substrates, introducing neuromorphic computing to large-area flexible electronics and opening up possibilities in brain-machine interfacing and adaptive learning of artificial organs.
1 van de Burgt et al. Nature Electronics, 2018
2 van de Burgt et al. Nature Materials, 2017
3 Keene et al. J Phys D, 2018
4:45 PM - BM07.02.08/EP05.02.08
Anisotropic Conducting Polymer Films for Bioelectronics
Patricia Jastrzebska-Perfec1,Georgios Spyropoulos1,Jennifer Gelinas1,Dion Khodagholy1
Columbia University1Show Abstract
Anisotropic conductive films, which consist of electrically conductive particles dispersed in nonconductive media, are increasingly being applied to establish high-density electrical bonds between electronic boards and chips. However, current anisotropic composites utilize metallic particles, often nickel and epoxy-based media, that require high thermocompression energy for bonding. Therefore, they have limited applicability in thin-film, conformable, and plastic-based devices that are used in bioelectronic applications. Furthermore, these materials are not biocompatible, significantly limiting their use in biological systems. We hypothesized that replacing the metallic particles with conducting polymer particles combined with a biocompatible nonconducting matrix would address this limitation. We developed a novel anisotropic conducting polymer (ACP) consisting of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) conducting polymer particles dispersed in a matrix of crosslinked chitosan (CS). To determine the permeability of PEDOT:PSS to CS, we characterized the resistances of thin CS-based films sandwiched with PEDOT:PSS and gold pads. We investigated the particle size, structure, density and distribution of pure PEDOT:PSS particles and PEDOT:PSS-coated CS particles. The anisotropy was defined by the ratio of horizontal and vertical impedance between interconnects. We benchmarked the anisotropy of the developed ACPs by geometrically varying an array of gold electrodes. The final ACP, which was created at 70°C with minimal pressure, yielded anisotropy of 105-106. The ACP was then used to maintain precise connections between a high density conformable implantable neural probe and back-end electronics. It enabled complete chronic in vivoimplantation of these electronics with minimal encapsulation layers, highlighting applicability for use in bioelectronic and clinical devices
Andreas Offenhäusser, Forschungszentrum Juelich
Roisin Owens, University of Cambridge
Sahika Inal, King Abdullah University of Science and Technology
Christian B. Nielsen, Queen Mary University of London
BM07.03: Neural Interfacing/Implantable Devices I
Tuesday AM, November 27, 2018
Sheraton, 2nd Floor, Constitution B
8:00 AM - BM07.03.01
Toward Biocompatible and Degradable Electronics—A Comprehensive Material Approach
Ashkan Shafiee1,Elham Ghadiri2,Kunzhao Li2,Anthony Atala1
Wake Forest School of Medicine1,Wake Forest University2Show Abstract
Over the past 10 years, regenerative medicine has witnessed a significant technological and scientific advancement. For instance, numerous revolutionary progress in stem cell science as well as additive manufacturing, namely 3D printing, have opened up new horizons in research and brought them closer to reality than ever before. However, for more sophisticated indications, fabrication of biological structures such as human tissues and organs may require an optimized procedure to obtain the impeccable final product. Therefore, the need for biocompatible electronic devices is a focus of attention in academia and industry. Moreover, biodegradable electronic devices for healthcare applications can also produce a revolution in the electronics industry and reduce electronic waste products. Currently, thousands of tons of silicon that is used to manufacture computers, cell phones, and other devices are discarded into the environment annually. It is critical that such waste be curtailed. Here, we report a systematic investigation on finding biocompatible/degradable functional electronic materials. To address this aim two different approaches were employed: 1-study the electronic properties of biomaterials, 2- study the biocompatibility of functional electronic materials. Materials with energy band gap between 1 to 3 eV are categorized as semiconductors and bigger than 3 eV as insulators. Various biomaterials were sought in terms of energy band diagram. Most biomaterials showed energy band gap bigger than 3 eV confirming them as insulators, for example, fibrinogen, glycerol, and gelatin showed 3.54, 3.02, 3.0 eV. Meanwhile, a few biomaterials were found as semiconductors such as phenol red in the cell culture medium with 1.96 eV energy band gap. On the other hand, the biocompatibility of organic semiconductors, such as P3HT and PCBM for different cell types such as satellite cells were examined. The cells were exposed to the thin layer of films prepared with the organic materials, and essential biomarkers (Desmin and MF20) were used to determine the consequence effect on the cells, their functionality, proliferation, and differentiation. The outcomes of this research can be used to fabricate biocompatible/degradable electronic devices for medical applications.
8:15 AM - BM07.03.02
Nanoelectrode-Integrated Polymer Fiber Probes for Chronic Neural Interfacing
Shan Jiang1,Kelly Kedlec1,Ana Marcano1,Junyeob Song1,William Mills1,Ian Kimbrough1,Harald Sontheimer1,Wei Zhou1,Xiaoting Jia1
Virginia Tech1Show Abstract
Deciphering complex neural circuits relies on the developments of neural interface devices with good biocompatibility, mechanical compliance, high spatial resolution, and high quality recording. There has been significant development in neural interface devices in the past decades, mostly based on silicon and metal electrodes or contact printed film electrodes. More recently, thermally drawn polymer fibers have been utilized as neural recording probes which exhibit good flexibility and biocompatibility. However, due to the low conductivity of conventional polymer electrodes, the size of a polymer fiber probe is typically much larger compared to the size of a single neuron in order to have the overall impedance fall in the recordable range, resulting in a poor spatial resolution of these probes. Therefore, it is of great importance to reduce the impedance of the polymer electrode while maintaining the miniaturized footprint in order to increase the spatial resolution and minimize the brain damage. In this study, we deposited metallic nanostructures on the tip of the polymer fiber probe to enhance the electrical properties as well as the electrophysiological recording performance. Soft nanolithography patterning technique was utilized to create dense vertical 3D nanopillar nanoelectrodes on the small area of the flexible polymer fiber tips via gold nanohole array masks. Because of the large surface area of the nanopillar nanoelectrode structure, the resulting impedance of the modified electrode has been reduced to be able to capture neural signals. The power density of local field potential (LFP) from both the modified and unmodified electrode showed the better recording performance of the modified one. Finally, we evaluated these nanoelectrode integrated polymer fiber probes in terms of chronic recording and long term tissue response. These results show that nanoelectrode-based surface modification can significantly reduce the impedance of polymer electrodes, thus increase the spatial resolution and improve the electrophysiology recording performance of polymer fiber probes.
8:30 AM - *BM07.03.03
Large Scale Integrated Organic Transistors for High-Resolution Electrocorticography of the Human Brain
Columbia University1Show Abstract
As our understanding of the brain’s physiology and pathology progresses, increasingly sophisticated materials and technologies are required to advance discoveries in systems neuroscience and develop more effective diagnostics and treatments for neuropsychiatric disease. Localizing brain signals may assist with tissue resection and intervention strategies in patients with such diseases. Precise localization requires large and continuous coverage of cortical areas with high-density recording from populations of neurons while minimizing invasiveness and adverse events. We describe a large-scale, high-density, organic electronic–based, conformable neural interface device (NeuroGrid) with embedded integrated circuitry capable of simultaneously recording local field potentials (LFPs) and action potentials from the cortical surface. We demonstrate the feasibility and safety recording with such devices in anesthetized and awake subjects. Highly localized and traveling physiological and pathological LFP patterns were recorded, and correlated neural firing provided evidence about their local generation. Application of NeuroGrid technology to 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.
9:00 AM - BM07.03.04
Deposition and Improved Adhesion of PEDOT on Microelectrodes
Côme Bodart1,Danny Chhin2,Nicolò Rossetti1,Pauline Chevreau1,Steen Schougaard2,Fabio Cicoira1
Polytechnique Montréal1,Université du Québec2Show Abstract
Adhesion quality and biocompatibility are the main obstacles to a successful use of conducting polymers coatings on metal microelectrodes for recording and stimulation. Such microelectrodes have very small dimensions, resulting in a high impedance. One way to address this problem is to deposit a conducting polymer, PEDOT, on their electroactive area to lower the impedance and reduce the foreign body reaction . However, the small size of such microelectrodes and the poor adhesion of conducting polymers on most inorganic substrates remain practical difficulties for large scale production. In our recent experiments using electrochemical polymerization, we explored the influence of different solvents (acetonitrile, propylene carbonate)  and electropolymerisation methods (potentiodynamic, galvanostatic, pulsed deposition) on the adhesion of an electropolymerized thin layer of PEDOT:BF4 on platinum electrodes. We also investigated the use of a diazonium salt as an anchoring layer for PEDOT on platinum . We evaluated the stability of our PEDOT-coated electrodes ex vivo by passive aging in physiological solutions and under repeated electrical stimulations, similar to those used for deep drain stimulation. Finally, we investigated in vivo aging to hopefully gain more insights on the stability of our PEDOT coating in contact with living tissues.
 Ludwig, K. A., Uram, J. D., Yang, J., Martin, D. C., & Kipke, D. R. (2006). Chronic neural recordings using silicon microelectrode arrays electrochemically deposited with a poly (3, 4-ethylenedioxythiophene)(PEDOT) film. Journal of neural engineering, 3(1), 59.
 Poverenov, E., Li, M., Bitler, A., & Bendikov, M. (2010). Major effect of electropolymerization solvent on morphology and electrochromic properties of PEDOT films. Chemistry of Materials, 22(13), 4019-4025.
 Chhin D., Polcari D., Bodart-Le Guen C., Tomasello G., Cicoira F., Schougaard S. Diazonium-based anchoring of PEDOT on Pt/Ir electrodes via Diazonium Chemistry. Journal of The Electrochemical Society. (publication pending)
9:15 AM - BM07.03.05
Transparent Arrays of Bilayer-Nanomesh Microelectrodes for Simultaneous Electrophysiology and 2-Photon Imaging in the Brain
Yi Qiang1,Kyung Jin Seo1,Pietro Artoni2,Michela Fagiolini2,Hui Fang1
Northeastern University1,Center for Life Science, Boston Children’s Hospital2Show Abstract
Transparent microelectrode arrays have emerged as promising tools for measuring neural signals with high spatiotemporal resolution by combining simultaneous electrophysiology and optical modalities. However, scaling down transparent microelectrodes to the size of single neuron is challenging since traditional transparent conductors are limited by their capacitive electrode/electrolyte interface. By reliably stacking individual layers of metal and low-impedance coatings in a same nanomeshed pattern, we demonstrated an innovative bilayer nanomesh approach to address this limitation with system-level, high electrode performance. Specifically, we successfully achieved Au/PEDOT:PSS bilayer nanomesh microelectrodes with site area down to ~ 314 μm2, comparable to the size of a single neuron, while possessing impedance of 130 kΩ at 1 kHz. Furthermore, fabricated 32-channel bilayer-nanomesh microelectrode arrays(MEA) have demonstrated over 90% yield on average, with down to 10% impedance variation among all electrode channels. Meanwhile, the bilayer nanomesh MEAs showed excellent compatibility with state of the art Ultra-Wide Band links for wireless recording and real-time stimulation artifact cancellation with a 100,000× signal/error ratio. Finally, in vivo electrophysiology recording with simultaneous 2-photon imaging on the mice visual cortex further validated the functionality and significance of our transparent MEA. The highly-transparent 32-channel bilayer nanomesh MEA allowed both wide-field epifluorescence and 2-photon Ca++ imaging of visual cortex and surrounding areas with successful detection of visual evoked potentials from multi-unit activity, while with no significant inflammation of the cortex due to the MEA implantation after 20 days. The results here established the bilayer nanomesh microelectrode approach as a practical pathway towards large-scale, high-density transparent arrays, with broad utility in neuroscience and medical practices.
9:30 AM - *BM07.03.06
Graphene-Based Neural Interfaces for Probing Brain Activity
Duygu Kuzum1,Yichen Lu1,Xin Liu1
University of California, San Diego1Show Abstract
The complexity of neural activities has challenged both neuroscience research and clinical practice for decades. Understanding neuronal dynamics and information processing performed by neural populations requires advanced technologies with high-resolution sensing and stimulation capability. Clinical neuromodulation therapies widely used for neurological disorders also depend on the ability to manipulate the dynamics of neural circuits. Conventional neural interfaces offering electrical, optical, or chemical signals have greatly advanced our understanding of neural functions, however, most of these technologies are based on a single functionality. Combining multiple functionalities in a single system has recently been pursued as an integrative approach in new neurotechnology development. Graphene has recently emerged as a neural interface material offering several outstanding properties, such as optical transparency, flexibility, high conductivity, functionalization and biocompatibility. The unique combination of these properties in a single material system makes graphene an attractive choice for multi-modal probing of neural activity. In this talk, I will present our recent work on graphene-based neural interfaces, highlight key applications, and finally discuss future directions and potential advances for graphene-based neurotechnologies in both basic neuroscience research and medical applications.
10:30 AM - BM07.03.07
A Soft, Conformable, Stretchable Sensor to Record Bladder Wall Stretch
Marc Ramuz1,Stuart Hannah1
Ecole des Mines de Saint Etienne - Centre Microelectronique de Provence1Show Abstract
A soft, fully biocompatible, stretchable strain sensor device based on ultra-thin stretchable electronics is reported. The sensor is able to monitor stretch of the bladder wall, via a resistive strain sensing approach. The stretchable sensor is used to determine bladder stretch, and hence volume, without the need for complex and invasive surgical procedures used currently, enabling the development of new safer and cheaper treatment options for various urological conditions. Such instances where a means to monitor bladder stretch could be invaluable are for sufferers of overactive bladder syndrome (OAB), urinary urge incontinence or after spinal cord injury.
Thermally evaporated Cr/Au thin films (~ 150 nm) on compliant, stretchable polyurethane (PU) film (≤ 50 µm), were deposited to produce resistive sensors. The sensors were patterned into a ‘dogbone’ design by laser patterning, with sensor W and L dimensions on the mm scale. The sensors display a linear response as a function of strain from 0 to 50 %, and as sensor length increases, sensor sensitivity as a function of strain increases. We show that the sensitivity is highest for L = 6 mm, at 3.18 Ω/%-strain, which is around 15 times higher than the sensitivity for L = 2 mm, at 0.21 Ω/%-strain. Furthermore, cycling tests performed on sensors of various length reveal that the devices display good stability, with virtually no hysteresis.
The highest sensitivity sensors were subsequently tested in vitro on an isolated pig bladder. The sensors were attached onto the external wall of the bladder using a biocompatible hydrogel adhesive. The bladder was repeatedly filled and emptied using a syringe system designed to mimic natural bladder behaviour. As bladder volume changes, the sensor changes resistance as a function of stretch, and displays very good repeatability over several bladder filling/emptying cycles. We found a maximum sensitivity of 0.1 Ω/ml for the most sensitive device. Our sensors pave the way towards completely implantable health monitoring systems of the future.
10:45 AM - BM07.03.08
Silk-Inspired Neurotechnology—Soft, Conformal and Optically Transparent Silk Electrode Interfaces for the Cortex
Dr. Anoop Patil1,Nitish Thakor1,2
National University of Singapore1,Johns Hopkins University2Show Abstract
Neurotechnology provides a potential platform for novel material-based strategies that can refashion the existing neural interface technologies. The current widely-used neural interfaces are dry, brittle and inorganic in nature, warranting a new soft material candidate for the development of tissue-compliant and mechanically-robust electrode interfaces that show great affinity to the wet surfaces of the biological tissues. Here, we report, soft and excellently conformal electrode interfaces designed on hydrated silk films that can conform to the wet slimy surfaces of the rat cortex. To the best of our knowledge, this is the first such demonstration of functional silk electrical interfaces for the wet in vivo environs of the cortex. This work represents a significant step towards soft implantable bioelectronics.
Metallized silk substrate (~15 μm thick) carrying the gold electrode patterns (~ 100 nm thick) is integrated with a patterned silk superstrate (~15 μm thick) to yield a silk electrode array. A flexible interconnect is connected to the array to facilitate electrical readouts from the electrode sites. The silk arrays are then water-annealed (~12 h) to render them nontransient.
We deployed the silk arrays on the rat cortex (S1FL region) to demonstrate the in vivo applicability of the nontransient silk interfaces. We noted that the cortical array laminated conformably on the nonplanar surface of the cortex. A rat transient ischemia (TIA) model was employed to demonstrate ECoG recording capability of the silk array. ECoG recordings prior to (serving as baseline) and following induction of stroke provided functional validation of the silk cortical array. A cranial window was created to deploy the silk array. The cerebral blood vessel in which a blood clot is to be induced, was located. The ECoG array was then deployed upon the S1FL region of the cranial window. The selected cerebral blood vessel (diameter 80 μm) was observed clearly via the transparent silk window of the silk array. Injection of Rose Bengal and shining of laser light (CW laser, 532 nm) through the transparent silk substrate induced a blood clot in the cerebral blood vessel. The evoked potentials captured by the individual electrode sites of the silk array prior to the induction of stroke represent the baseline ECoG recordings. These recorded responses were evoked through forepaw stimulation. Induction of blood clot led to a suppression of the evoked ECoG activity, captured cleanly by the silk array.
In this work, we reported the feasibility of realizing nontransient soft conformal silk electrode arrays for interfacing with the cortical surface in rat model. We observed that the silk arrays are soft and could couple intimately to the wet surfaces of the rat cortex. To the best of our knowledge, this is the first such demonstration of silk neurotechnology for the cortex and can impact basic neuroscience research and clinical trial industry.
11:00 AM - BM07.03.10
Conductive Polymers Based Electrodes for Monitoring and Stimulating Neuromotor Functions in Small Animals
Nicolò Rossetti1,Ada Lee1,Prabhjot Luthra1,Michelle Gaspard1,Shalin Bhanot1,Côme Bodart1,Fabio Cicoira1
École Polytechnique de Montréal1Show Abstract
Conductive polymers have been widely explored as a coating of inorganic substrates for biological signal recording and stimulation, but their poor adhesion to inorganic substrates represents the main limit for their in vivo application and current solutions make use of long and complicated processing steps [1-3]. In this work, stainless steel wire electrodes composed of twisted wires have been coated with conductive polymers through electropolymerization for muscle signal recording in small animals. Two solutions consisting in Dopamine:Polypyrrole/PEDOT bilayer and PEDOT processed in propylene carbonate are proposed to increase the polymer adhesion to the metal. The electrodes have been electrochemically characterized, and the adhesion and electrochemical stability have been evaluated through ultrasonication and phosphate buffer solution soaking test. Our work gives new insights on the adhesion enhancement of conductive polymers to inorganic substrates allowing for simple and fast solutions that will improve the durability and efficiency of conductive polymer coated electrodes.
 S. Carli et al. "Conductive PEDOT Covalently Bound to Transparent FTO Electrodes," J. Phys. Chem. C, vol. 118, no. 30, pp. 16782-16790, 2014.
 L. Ouyang et al. "Enhanced PEDOT adhesion on solid substrates with electrografted P(EDOT-NH2)," Sci. Adv., vol. 3, no. 3, 2017.
 X. Luo et al. "Highly stable carbon nanotube doped poly(3,4-ethylenedioxythiophene) for chronic neural stimulation," Biomaterials, vol. 32, no. 24, pp. 5551-5557, 2011.
11:15 AM - *BM07.03.11
Engineering the Next Generation of Neurodevices—New Materials and Clinical Translation
University of Pennsylvania1Show Abstract
The incidence of neurological disorders like epilepsy, Parkinson’s disease, stroke, dementia, addiction and major mental illness is growing, as the world’s population ages. Response to medications for these conditions has plateaued, paving the way for a revolution in implantable devices as the next wave of effective treatments for these “brain network disorders.” Key to developing these new devices are advances in computation, batteries, sensors and closed loop algorithms. New and more versatile materials is one of the main requirements and drivers of innovation in new medical devices and technologies. In this lecture I will outline major applications in the area of neurodevices/ brain computer interfaces, present unmet needs, and discuss the path to clinically translate innovations from the laboratory to patients. I will give examples from our own research and other labs on this path, touch on common failure modes and novel tools for collaboration, bringing engineers, clinicians and industry together to advance clinical care.
BM07.04: Neural Interfacing/Implantable Devices II
Tuesday PM, November 27, 2018
Sheraton, 2nd Floor, Constitution B
1:30 PM - BM07.04.01
Highly Stable PEDOT-CNT Nanotube as Neural Electrode Coating
Nuan Chen1,Baiwen Luo1,Nitish Thakor1,Seeram Ramakrishna1
National University of Singapore1Show Abstract
During the past decades, neural electrodes have been developed as promising interface technology for direct communication with the neural tissues for diagnosis of the nervous disorders and treatment of the injury. Considering the significant material mismatch between the external implant and native tissue, a thin coating is employed on the electrode sites as an intermediate layer to bridge the difference. However, great challenges still exist regarding the long-term performance of the electrode coating in vivo.
In this study, a tubular electrode coating made of poly(3,4-ethylenedioxythiophene) (PEDOT) and carbon nanotube (CNT) was designed, targeted to long-term neural recording. The PEDOT-CNT nanotube coating was fabricated and showed compatibility with flexible polyimide electrode. The coating exhibited a 3D network-like structure made of hollow tube with an outer diameter of ~700nm and wall thickness of ~90nm. The electroactivity of the PEDOT-CNT coating was investigated using electrochemical impedance spectroscopy and cyclic voltammetry. The coated electrode sites showed significantly decreased impedance and increase charge storage capacity compared to bared site, which would allow more charge transfer at the interface and increase the sensitivity during neural recording. To test the mechanical adhesion of the PEDOT-CNT nanotube coating, ultrasonic treatment was employed in the study. The PEDOT-CNT nanotube could sustain 20min sonication with less than 20% delamination area while the PEDOT-PSS nanotube showed more than 60% delamination area after 5min treatment. The incorporation of CNT significantly reinforced the nanotube structure and improved the mechanical durability against sonication which would address the delamination issue of PEDOT coating and support chronic recording. We have also studies the different deposition condition and their effects on the morphology, electrical property and mechanical property of the coating. In vitro culture of neurons showed positive neuron attachment and neurite extension on PEDOT-CNT nanotube immobilized with poly-lysine and laminin.
1:45 PM - BM07.04.02
Conducting Polymers for Stretchable and Healable Electronics
Yang Li1,Fabio Cicoira1,Shiming Zhang2,Floriane Miquet-Westhpal1,Leslie Liu1
Ecole Polytechnique de Montreal1,University of California, Los Angeles2Show Abstract
Organic electronic devices, apart from consumer applications, are presently paving the path for key applications at the interface between electronics and biology. In such applications, organic polymers are very attractive candidates, due to their distinct properties of mechanical flexibility, self-healing and mixed conduction.
My group investigated the processing conditions leading to high electrical conductivity, long-term stability in aqueous media as well as robust mechanical properties of the conducting polymer poly(3,4-ethylenedioxythiophene) doped with polystyrenesulfonate (PEDOT:PSS) [1-3].We have demonstrated that stretchable PEDOT:PSS films can be achieved by adding a fluorosurfactant to the film processing mixture and by pre-stretching the substrate during film deposition. We have achieved patterning of organic materials on a wide range of substrates, using orthogonal lithography and pattern transfer [4-5]. Recently we have discovered that PEDOT:PSS films can be rapidly healed with water drops after being damaged with a sharp blade  or show autonomous self-healing if processed in presence of certain additives.
My talk will deal with processing, characterization and patterning of conducting polymer films and devices for flexible, stretchable and healable electronics. I will particularly focus on the strategies to achieve films with optimized electrical conductivity and mechanical properties, on unconventional micro patterning on flexible and stretchable substrates, on the different routes to achieve films stretchability and self-healing.
F. Cicoira et al. APL Mat.3, 014911, 2015.
F. Cicoira et al.Appl. Phys. Lett. 107,053303, 2015.
3. F. Cicoira, et al. Appl. Phys. Lett. 111, 093701, 2017
F. Cicoira et al. Chem. Mater. 29, 3126-3132, 2017.
F. Cicoira et al. J. Mater. Chem.C 4, 1382–85, 2016.
F. Cicoira et al. Adv. Mater.29, 1703098, 2017.
2:00 PM - *BM07.04.03
Multimodal Characterization of Soft Bioelectronics
Ecole Polytechnique Federale de Lausanne1Show Abstract
Soft bioelectronics incorporates all the functional attributes of conventional rigid electronics in formats that enable reversible mechanical loading and, in the case of implantables, performance under physiological conditions. Understanding the underlying mechanisms of stretchable materials and establishing the performance boundaries of such devices under the multiple operation conditions are fundamental to research efforts in the field. The biomedical context also imposes a challenging experimental environment that is difficult to replicate or predict. There is an unmet need for experimental set-ups that combine multiple modes of loading e.g. mechanical, thermal, electrical, biological, and provide real-time, concurrent probing of the devices.
This talk will describe our recent efforts in constructing multimodal experimental set-ups and establishing standardized tests and experiments that can clearly define the reliability and lifetime for soft bioelectronics. Using stretchable metallization integrated in wearable sensors and spinal implants as test vehicles for the new characterization platforms, we will report on failure modes, repeatability, robustness, and reliability. These metrics are often underestimated in academic research yet critical to advance the translation of soft bioelectronics.
2:30 PM - BM07.04.04
Chronic and Acute Stress Hormone Monitoring/Stimulation in Adrenal Gland
Yiel Jae Shin1,SungHyuk Sunwoo2,Tae-il Kim1
Sungkyunkwan University1,Seoul National University2Show Abstract
Living organisms mainly use nervous and endocrine systems to control the body and maintain homeostasis independently. Endocrinal signal based on the flow of special chemicals called hormone affects the body chronically and massively. When stress is applied to human body, hypothalamus releases corticotropin-releasing hormone (CRH) to the pituitary gland that generates adrenocorticotropic hormone (ACTH) which flows into the adrenal cortex, especially adrenal zona fasciculata (AZF) cell in adrenal gland. The adrenal cortex then produces cortisol, a stress hormone that rebalances body functions and performances of neural and muscular system. However, repeated and chronic stress can cause malfunctions in cortisol releasing endocrine system. Chronic stress involves accumulation of excessive and unnecessary cortisol that eventually cause several diseases such as amnesia, depression, fatigue, anxiety. It is necessary to continuously monitor the cortisol concentration to prevent such diseases which caused by chronic stress. Recently, it was revealed that the electrophysiological (EP) signal induced by ion flux through cellular membrane was responsible for hormone releasing process in corresponded endocrine organs. We assumed that accurate recording of electric signal representing physiological activities of endocrine cells could be applied to characterize cortisol change. Here, we introduce a long lasting, implantable Anchor - like flexible probe that can be used to quantify relationship between cortisol releasing level and electrophysiological (EP) signals from adrenal gland based on flexible EP sensors. This anchor – like probe penetrated through Adrenal Gland, which ensured minimal invasion to organs and stability, low impedance increment over 13 weeks. Through our research, we identified EP signal Frequency was increased in AZF cells, only induced by acute stress or ACTH injection. Thus, our team successfully determined activities of hormonal cells and relative change of cortisol hormone level under stress environment in in vivo animal model. Next, we hypothesized that electrical stimulation of surface of adrenal gland could improve or suppress activity of adrenal gland. We designed elastomer based, conformally attaching stretchable serpentine electrodes. It is known that cortisol secretion is also increased by not only stress but blood loss, therefore we extracted small doses of blood from inferior vena cava (IVC) of rat with every 5 minutes to induce artificial hemmorrhage. By comparing Cortisol concentration of Non - electrical stimulated rat with electrically stimulated showed us that high frequency electrical stimulation tend to suppress activity of AZF cell. However, low frequency electrical stimulation improved AZF cell activity, which showed higher cortisol concentration then standard cortisol concentration. This research of Adrenal gland could provide fundamental knowledge to medical applications such as stress regulator.
2:45 PM - BM07.04.05
Design of Conductive Gel for Sensing Weak Biosignals with High S/N Ratio
Yuki Noda1,Naomi Toyoshima1,Teppei Araki1,2,Shusuke Yoshimoto1,Takafumi Uemura1,2,Tsuyoshi Sekitani1,2
Institute of Scientific and Industrial Research, Osaka University1,Advanced Photonics and Biosensing Open Innovation Laboratory2Show Abstract
Conductive gel enabling precise measurement of weak electrical signals are desired for the detection of biomedical signals such as an electroencephalogram (EEG) or a fetal electrocardiogram (ECG). Since these signals are intrinsically weak less than 100 uV, the noise level has to be lowered to acquire signals with the high S/N. In general, one strategy for obtaining the high S/N ratio signal is to increase the electrode area to lower the contact resistance between skin and electrode or to shorten the length of the wiring to prevent invasion an external noise, however, we propose another option to detect signals with high quality by modifying gels on electrode. Here, we designed the biocompatible conductive gel to obtain weak EEG signals with the high S/N ratio by reducing the contact resistance and mains hum intensity.
The developed gels are based on Amylopectin contained in rice and NaCl. By just printing and heating the precursor solution on a noble metal, conductive gel can be fabricated. The impedance spectrum of gels shows almost frequency-independent characteristics through a range of 0.1 Hz to 100 kHz lower than 1kΩ. Hydrogen-boded network of Amylopectin gives sufficiently strong adhesive force to the skin with its strength comparable to adhesive plasters. Other components enable to suppress mains hum that is one of the origin of lowing the S/N ratio of EEG signals. By combining the developed gels and the wireless measurement system, we successfully obtained EEG signals from forehead. As with Ten20 conductive paste that is commonly used to measure EEG signals in hospitals, the developed gels can also detect representative brain wave like alpha waves that appears at 10 Hz when eyes are closed. Additionally, the intensity of mains hum appeared between 50-60 Hz are effectively suppressed to about 50% against that of Ten20 conductive paste, meaning that we obtained EEG signals with the high S/N ratio. Our rational design of the biocompatible conductive gel may usher a new strategy for fabrication of "noise-reducing material” in the field of electrical and material science.
3:30 PM - *BM07.04.06
Bioelectronics with Nanocarbons—From Transparent to Fuzzy Interfaces
Carnegie Mellon University1Show Abstract
We focus on developing a new class of nanoscale materials and novel strategies for the investigation of biological entities at multiple length scales, from the molecular level to complex cellular networks. Our highly flexible bottom-up nanomaterials synthesis capabilities allow us to form unique hybrid-nanomaterials. Recently, we have demonstrated highly controlled synthesis of 3D out-of-plane single- to few-layer fuzzy graphene (3DFG) on a Si nanowire (SiNW) mesh template. By varying graphene growth conditions, we control the size, density, and electrical properties of the NW templated 3DFG (NT-3DFG). This flexible synthesis inspires formation of complex hybrid-nanomaterials with tailored optical and electrical properties to be used in future applications such as biosensing, and bioelectronics. Currently, we target the limits of cell-device interfaces using out-of-plane grown 3DFG, aiming at electrical recordings with subcellular spatial resolution (<5μm) and μsec temporal resolution. Last, we have developed a unique transparent graphene-based electrical platform that enables concurrent electrical and optical investigation of ES-derived cardiomyocytes’ intracellular processes and intercellular communication. In summary, the exceptional synthetic control and flexible assembly of nanomaterials provide powerful tools for fundamental studies and applications in life science, and open up the potential to seamlessly merge either nanomaterials-based platforms or unique nanosensor geometries and topologies with cells, fusing nonliving and living systems together.
4:00 PM - BM07.04.07
Bioinspired Nanowire Devices Utilizing Perylene Diimides
Jason Slinker1,Kuo-Yao Lin1,Andrew Bartlett2,Alon Gorodetsky2
The University of Texas at Dallas1,The University of California-Irvine2Show Abstract
Despite remarkable examples of difficult-to-produce isolated molecular devices, the scalable nanomanufacturing of such electronics remains at a standstill due to fundamental roadblocks associated with the synthesis of large quantities of modular nanoscale circuit elements. We have introduced a methodology for rapid, scalable production and facile purification of nanowire devices. We have synthesized organic semiconductor moieties, perylene-3,4,9,10-tetracarboxylic diimides (PTCDIs), within DNA-like scaffolds, leveraging the rapid, efficient, and precise coupling afforded by traditional DNA bioconjugate chemistry. These DNA-inspired nanowires enable the self-assembly of active, nanoscale circuit elements at patterned electrodes. The assembly and electrical performance of these arrayed devices have been characterized through scanning microscopy techniques and custom, automated electrical probe measurements under controlled environments and temperature. Current voltage characterization revealed absolute currents of fully well matched duplexes incorporating perylene units were enhanced by twofold over such nanowires incorporating two C-A mismatches and 4.4 fold over conventional DNA nanowires. Temperature dependence revealed a sharp current drop with temperature consistent with the dissociation of the modular duplex. Our unique and economically viable approach offers a new paradigm for the fabrication of nanoscale electronic circuits.
4:15 PM - *BM07.04.08
Ink-Jet Printed 3D-Microelectrode Arrays for Neuroelectronic Interfaces and Sensing Applications
Bernhard Wolfrum1,3,Nouran Adly1,Leroy Grob1,Philipp Rinklin1,Sabine Zips1,Lennart Weiss1,Hideaki Yamamoto2,Ayumi Hirano-Iwata2
Technical University of Munich1,Tohoku University2,Forschungszentrum Jülich GmbH3Show Abstract
Microelectrode arrays are used in a variety of sensing and stimulation applications including electrochemical biosensor platforms and neuroelectronic interfaces. Typically those arrays are produced with state-of-the-art fabrication methods such as photolithography or electron beam lithography, which provide high-resolution capabilities to include thousands of electrodes on a single chip. However, often these methods are expensive and restricted to certain substrate or electrode materials. Thus, they are not ideally suited for low-cost rapid prototyping of devices with alternative geometric features or materials.
Inkjet printing is an alternative low-cost fabrication method that has contributed to the field of printed electronics, recently including the generation of microelectrode arrays. Being an additive process, the material consumption is low and the method can be applied to generate functional structures on a variety of substrates including soft materials such as hydrogels. An inherent disadvantage of this technology however, is the poor lateral resolution, which is typically limited to approximately 20 - 30 µm using conventional inkjet printing platforms. Thus, it is not likely that inkjet printing will be able to compete with standard microfabrication techniques in terms of lateral sensor density. Yet, we show that some of the drawbacks concerning the lateral resolution in inkjet printing can be compensated using 3D-printing approaches. We demonstrate that the distance between individually addressable electrodes can be tuned to ~1 µm in lateral and ~100 nm in vertical direction, which is exploited in electrochemical sensors using redox cycling amplification strategies. Furthermore, we show the possibility of generating defined high-aspect ratio 3D-microelectrode arrays on various substrates with an electrode height of more than 70 µm and electrode radius in the micrometer range. The flexibility of this process allows the fabrication of tailored devices for 3D-neuroelectronic interfaces on rigid as well as soft substrates.
4:45 PM - BM07.04.09
Ti3C2 MXene Neural Electrodes for Sensitive Detection of Neuronal Spiking Activity
Nicolette Driscoll1,2,Andrew Richardson1,Kathleen Maleski3,Babak Anasori3,Oladayo Adewole1,2,Pavel Lelyukh3,Lilia Escobedo4,D. Cullen1,2,Timothy Lucas1,Yury Gogotsi3,Flavia Vitale1,2
University of Pennsylvania1,Corporal Michael J. Crescenz Veterans Affairs Medical Center2,Drexel University3,Cornell University4Show Abstract
High-resolution neural interfaces are essential tools for studying neural circuits underlying brain function and disease. As electrodes are miniaturized to achieve high spatial resolution and resolve individual neuronal spiking activity, maintaining low impedance and high signal quality becomes a significant challenge. Nanostructured materials have the potential to address this challenge by offering a combination of unique electrical and mechanical properties and the ability to interact with biological systems on a molecular scale. Ti3C2 MXene, a recently discovered 2D nanomaterial, possesses remarkably high volumetric capacitance, conductivity, surface functionality, and processability in aqueous dispersions, making it unique among 2D nanomaterials. In this work, we seek to evaluate the recording performance of MXene for detection of neuronal spiking activity in vivo. We employed a high-throughput microfabrication process for micropattering MXene onto flexible, parylene-C substrates, and fabricated a 10-channel laminar probe. The laminar probe has 5 sets of side-by-side MXene and gold (Au) electrode contacts (25 µm diameter) arranged in a stereotrode configuration to enable direct comparison of signal quality between the two materials during in vivo recording. Electrochemical impedance spectroscopy revealed that the MXene electrodes in the array exhibit remarkably low 1 kHz impedance compared to their Au counterparts: 219 ± 31 kΩ vs. 865 ± 125 kΩ, respectively. The MXene electrodes have a rough and layered surface morphology (Ra = 32 nm), which likely contributes to their ~4x improvement in impedance properties compared to Au. We performed acute recording experiments in anesthetized rats and recorded multiunit neural spiking activity on adjacent MXene and Au stereotrode contacts implanted in sensorimotor cortex. Spikes that occurred simultaneously on adjacent MXene and Au electrodes were considered to have been generated by the same neuron, and their signal-to-noise ratios (SNR) were computed and compared. We found that MXene electrodes recorded neural spiking activity with significantly higher SNR than Au electrodes. We also found that MXene electrodes recorded more spikes overall than the Au electrodes, and that the spikes unique to the MXene electrode in a stereotrode pair tended to be low amplitude, suggesting that MXene electrodes have a larger “seeing distance”, allowing them to resolve spiking activity from a larger volume of tissue. Finally, we assessed the neuronal biocompatibility of Ti3C2 MXene in vitro and found that neurons cultured on MXene films proliferated, showed axonal growth, formed synaptic connections, and were as viable as control cultures. This work highlights the suitability of Ti3C2 MXene for high resolution neural interfaces and suggests that MXene has significant potential to enhance the performance of neural microelectrodes beyond current capabilities.
BM07.05: Poster Session I: Bioelectronics—Fundamentals, Materials and Devices
Christian B. Nielsen
Wednesday AM, November 28, 2018
Hynes, Level 1, Hall B
8:00 PM - BM07.05.01
Wireless Flexible Vertical GaN MicroLEDs for Transparent Optical Stimulator
Han Eol Lee1,Jung Ho Shin1,Jung Hwan Park1,Jae Hee Lee1,Keon Jae Lee1
With the advent of the hyperconnected era, visual IoT devices attracted great interest. Flexible displays are powerful candidates for interactive visual communication. Inorganic-based micro light emitting diodes (μLEDs) have been regarded as key technologies in RGB micro LED TVs due to their excellent electrical/optical properties, fast response, long lifetime and high stability in harsh environments. Several groups have studied various inorganic LED materials for various applications. Despite previous reports of flexible micro LEDs, GaN f-VLEDs on plastic substrates have not yet been demonstrated due to the difficulty of vertical GaN interconnections. Flexible energy sources for f-LEDs are also required for practical applications of flexible optoelectronic systems.
Herein, we report a flexible 30x30 GaN VLED array through a simple manufacturing process. The GaN LED chip was separated from the sapphire wafer by the ILLO process. Stand-alone microLEDs are isolated by biocompatible layers and are interconnected vertically with AgNW-based conductors by resolving the high step coverage of f-VLEDs. Ultra-thin, transparent and flexible GaN VLEDs are attached to the human nail in an conformal structure with high light output of 30 mW mm-2. The lifetime of the f-VLED was experimentally investigated by a high accelerated stress test (HAST) and theoretically estimated by simulation. In addition, our f-VLEDs exhibited excellent mechanical durability during cyclic bending cycles. A wireless power supply system for human skin has been successfully demonstrated by delivering electrical energy to the f-VLED. Finally, the blue f-VLED successfully emitted blue light into the mouse brain without severe tissue damage.
8:00 PM - BM07.05.02
Metal Nanoparticles-Grafted Functionalized Graphene Coated with Nanostructured Polyaniline ‘Hybrid’ Nanocomposites as High-Performance Biosensors
Sanju Gupta1,Romney Meek1
Western Kentucky University1Show Abstract
We report on the development of next-generation chemical, electrochemical and biological sensors from nanocomposites with broader electrical conductivity and anticipated linear sensitivity, faster response time, specificity and stability. We synthesized metal nanoparticles-grafted functionalized graphene nanosheets with nanostructured polyaniline (PANi) ‘hybrid’ nanocomposites for ascorbic acid (AA) sensing. The versatility of the nanocomposite performance was corroborated by altering the size and areal density of electrodeposited gold (AuNP) and silver (AgNP) nanoparticles on the graphene-family nanomaterials; GFNs namely, graphene oxide; GO, thermally reduced GO; rGOth and nitrogenated functionalized graphene; NFG. In addition, the globular surface morphology and charge density of electropolymerized polyaniline (PANi) onto GFNs can also influence the biosensor performance. The noble metal nanoparticles are selected due to their higher electrical conductivity, facile synthesis, easier processability, antimicrobial applicability and scalability. The as-synthesized multilayer architectures (PANi|AgNP|GFN and PANi|AuNP|GFN) on fluoride-doped tin oxide (FTO) coated glass, graphite foil (GF) and graphene rod (GR) electrodes increased the electrical conductivity of the electrodes significantly and reduced the charge transfer resistance dramatically determined while investigating the electrochemical and biosensing properties. We demonstrate the high-performance sensing for the detection of AA analyte over a full detection range (from 1 x 10-12 M to 10 x 10-3 M) with linear sensitivity of 10 mA mM-1 cm-2 and excellent limit of AA detection < 1pM with higher signal-to-noise ratio following PANi|AuNP|NFG £ PANi|AgNP|NFG < AuNP|NFG < AgNP|NFG. The specificity of the biosensor is also assessed by interaction of electroactive components with AA interfering species commonly found in blood serum samples i.e. glucose (Glu) and uric acid (UA). We attribute these findings to synergistic coupling of electrochemically bridged metal nanoparticles and functionalized graphene doped with nitrogen that promotes localized orbital re-hybridization and heterogeneous integration with PANi. They all contribute toward enhanced electroactivity and ensure rapid charge transfer and ion conduction. These multilayer ‘hybrid’ nanocomposite electrodes are also useful as advanced electroanalytical platforms for platinum-free electrocatalysis, electrodes for energy storage pseudocapacitors and enriching biofuel cell development. This work is supported in parts by KY NSF EPSCoR Grant and WKU Graduate School Fellowship.
8:00 PM - BM07.05.03
Biosensor for the Simultaneous Monitoring of Breath Isoprene and Acetone
Jan van den Broek1,Amy Wang1,Andreas Güntner1,Sotiris Pratsinis1
ETH Zürich1Show Abstract
Volatiles from the human body, especially from breath, contain a wealth of physiological and pathological information.1 Chemo-resistive metal-oxide gas sensors stand at the interface to the human biosystem as they specifically interact with such biomarkers and are capable to measure their concentrations even at the lowest parts-per-billion (ppb) levels.2 This way, individual emanating volatiles can be monitored to infer and better understand metabolic states and processes. In specific, breath isoprene has been suggested to be an indicator for the efficacy of blood cholesterol-lowering therapy3 and cardiac output,4 while acetone is an established biomarker for fat metabolism.5 Thus, online monitoring of these two gases simultaneously by a portable device can be a promising tool to optimize effective weight loss through physical exercise and diet planning.
Here, we present a sensor system for the simultaneous detection of isoprene and acetone in complex breath mixtures. It consists of nanostructured films of inorganic metal-oxides designed by flame aerosol synthesis to selectively interact with these biomarkers on a molecular level, resulting in a detectable electrical signal. The resulting biosensor can detect acetone and isoprene simultaneously down to 5 ppb in real time at breath-relevant relative humidity. It shows high selectivity to other major breath markers like methanol, ethanol and ammonia. The biosensor is also tested in vivo by direct sampling of breath through a breath sampler and simultaneously cross-validated by state-of-the-art mass spectrometry. All the components utilized can be readily miniaturized and integrated into a portable device enabling monitoring of these important metabolic tracers.
1. M. Righettoni, A. Amann, S. E. Pratsinis, Mater Today, 2015, 18, 163-171.
2. J. van den Broek, A. T. Güntner, S. E. Pratsinis, ACS Sens, 2018, 3, 677-683.
3. B. G. Stone, T. J. Besse, W. C. Duane, C. D. Evans, E. G. DeMaster, Lipids, 1993, 28, 705-708.
4. T. Karl, P. Prazeller, D. Mayr, A. Jordan, J. Rieder, R. Fall, W. Lindinger, J Appl Physiol, 2001, 91, 762-770.
5. A. T. Güntner, N. A. Sievi, S. J. Theodore, T. Gulich, M. Kohler, S. E. Pratsinis, Anal Chem, 2017, 89, 10578-10584.
8:00 PM - BM07.05.04
Transparent, Flexible Deep-Well Micro-Structured PEDOT:PSS/Au Nanorods Based Electrode Array for Neural Recording
Younguk Cho1,Ki Jun Yu1
Yonsei University1Show Abstract
Neural interfaces offer an insight into the mechanism of nervous system by recording signals from neurons. Conventional neuro-electrodes are made of metal that may occur clinical image distortion by its inherent opacity. Electrode transparency is ultimately important factor, because electrical artifacts from light stimulation for opto-genetics hinder the neural recording and interfere with the pinpoint control of neural activity. Ultrathin metal based devices for neural recording have been reported as alternatives with transparency, but the relatively low transmittance rate (<60%) requires novel materials and micro/nanopatterning techniques that offer significant enhancement of signal to noise ratio(SNR) of electrophysiological signals while maintaining its transparency.
Biocompatibility is also important factor to be considered for electrodes that are used for implantable neural arrays. Numerous materials for biocompatible implantable devices with the outstanding electrical properties have been discussed for the electrophysiological recordings or stimulations. However, only small number of reported such electrodes satisfy the conditions where multiple characteristics such as high transparency, flexibility, and high SNR, together with credible bio-stable property require, thereby enabling conformal electrical and optical neural recording simultaneously. Conducting polymers are excellent material choice for the neural electrodes that satisfy the characteristics mentioned above. Recently, poly(3,4-ethylenedioxythiophene)(PEDOT) as the representative conducting polymer is widely used for the neural electrodes due to the good conductivity with a high degree of an optical transparency.
Herein, we present a facile fabrication of deep-well structured PEDOT:PSS/Au nanorods array that can greatly improves SNR of neural recordings compared to the conventional PEDOT:PSS based electrodes. In our work, Au nanorods with three-dimensional(3D) deep-well microstructures by self-assembly are exploited as particles that can greatly enhance electrode conductivity while maintaining its optical transparency. Au nanorods are also suitable for the implantable neural interface design because of its well-known biocompatibility. Electrical and optical characterizations were conducted on both the deep-well microstructure and the plain surface-based PEDOT:PSS/Au nanorod electrode as a point of comparison. These experimental results show the much lower impedance plot and higher optical transparency with the deep-well surface structure compared to that with the planar device. Conducting cytotoxicity and implantation experiments on animal models also support its good biocompatibility. We expect this novel microstructure electrode array to be the unprecedented candidates for electrodes in a field of biomedical engineering such as an implantable cell regulating device or neural interface.
8:00 PM - BM07.05.05
Sensing Applications of Remote-Gate Field-Effect Transistor Combining Polymer Sensing Membrane
Hyun-June Jang1,Justine Wagner1,Hui Li1,Qingyang Zhang1,Taein Lee1,Jian Song1,Howard Katz1
Johns Hopkins University1Show Abstract
A field-effect transistor (FET) sensor electrically quantifies analyte levels through the perturbation of source-drain currents by chemical interactions at the gate in a label-free manner. In a typical scheme in FET sensors, specific receptors are placed on the semiconducting layer or the gate of FETs which acts as the sensing layer. There have been many attempts to apply organic/polymer materials in FET sensors due to their unique intrinsic properties such as flexibility and transparency which promotes the FET sensor as a cost-effective means on wearable platforms. However, an immense challenge exists in regards to using organic/polymer materials as the semiconductors, because of their instability under solution-based testing. Water on the dielectrics of OFET biosensors diffuses into the organic semiconducting layer and degrades its semiconducting character.
Therefore, having a remote gate geometry, which separates the sensing component from the FET transducer, is highly desirable for OFET biosensors. This remote gate structure not only protects the semiconductor from damage by solution, but also harnesses the aforementioned advantages of using organic/polymer materials in the sensor platforms. Alternatively, the OFET transducer can be replaced with inorganic FETs that have much higher stability. This is because the essential function of a FET is just to translate input voltage signals from the gate electrodes into output signals in the drain and the sensing membrane, not the FET, crucially determines sensitivity, specificity, and characters of the sensing platform.
Herein, we demonstrate three diverse sensor applications based on the usage of commercial field-effect transistors with remote polymer gate: cortisol sensor, pH sensor, and dopant monitoring sensor. All of these sensors share the same detection system but use different remote polymer sensing membranes. In cortisol sensors, the polymer sensing membrane was made by linking poly(styrene-co-methacrylic acid) (PSMA) with anti-cortisol before coating the modified polymer on the remote gate. The embedded structure of the anti-cortisol in the polymer allowed cortisol molecules to bind near the membrane-substrate interface. A limit of detection of 1 ng/mL was shown in lightly buffered artificial sweat. In the second application, we investigated the intrinsic pH sensitivity of polystyrene, poly(methyl methacrylate), and PSMA, by ranging the pH from 3 to 11. The long and short-term pH sensitivity exposure was compared for each individual polymer. In our last application, we demonstrate new way to quantify dopants concentration on polymers using the remote gate geometric approach. P3HT was deposited on the remote gate structure and the dopant, F4TCNQ, was dissolved in acetonitrile and deposited onto the P3HT layer. We were able to quantify and evaluate the deposition from solutions with varying concentrations of dopant which ranged from 1ug/ml to 1 mg/ml in contact with the P3HT layer.
8:00 PM - BM07.05.06
Eco-Friendly Biodegradable Thin-Film Transistor and Floating Gate Memory Using Indigo Organic Semiconductor
Pilwoo Lee1,Hunsang Jung1,Wonkyu Kang1,Kyoungmin Woo1,Hyun Ho Lee1
Myongji University1Show Abstract
In this study, eco-friendly and biodegradable thin film transistor (TFT) devices having floating gate (FG) for memory charging operation have been demonstrated. All materials for fabrications of TFT and its memory TFT were originated from biologically produced and environmentally friendly substrates, where related researches have been in spotlight in order to accomplish an entirely biodegradable electronics.
As a semiconductor material, indigo has been continuously adopted, in literatures which is a natural pigment from plant. The devices have been fabricated on biodegradable carboxymethyl cellulose (CMC) substrate. Gold as a gate electrode was deposited on CMC substrate. Gate dielectric layer was based on lactose or lactose oligomer, which was also known as a good performanced dielectric layer with low dielectric losses. The FG material for memory device was also adopted from biological nanoparticles (NPs) such as polylysine, which could be formulated by polymerization of amino acid of lysine. Before an implementation of TFTs on the CMC, all TFTs and memory TFTs could be accomplished on Si substrate. Through this kind of degradable electronic study, recent environmental problems associated with non-degradable plastic could be reduced or eventually resolved in the furture.
8:00 PM - BM07.05.07
Ternary Metal Chalcogenide (Ni, Co)0.85Se for Biosensing Applications
Niman Alshareef1,Manuel Quevedo-Lopez1
University of Texas at Dallas1Show Abstract
Ternary transition metal chalcogenides are an emerging class of materials for a variety of electrochemical and energy applications. Among, them (Ni, Co)0.85Se is an interesting compound because it exhibits several attractive features including: (1) high electrochemical activity due to the presence of electroactive Ni and Co atoms, (2) metallic-like conductivity, which ensures rapid electron transport, (3) ease of nanostructure formation.
Here we report a simple two-step hydrothermal process to synthesize nanostructured (Ni, Co)0.85Se. Briefly, sacrificial template of Ni–Co-precursor was first synthesized using a hydrothermal method. In a subsequent step, the Ni–Co precursor was chemically converted into (Ni, Co)0.85Se by selenization in NaHSe solution, resulting in a uniform distribution of Ni, Co, and Se. Thanks to its unique properties, we have implemented (Ni, Co)0.85Se for biosensing application first as generic H2O2 sensor, and then as enzymatic sensor for glucose, uric and ascorbic acids. H2O2 sensing measurements were performed using 0.1 M PBS as supporting electrolyte under ambient conditions using CV, LSV, and amperometry techniques. The fabricated sensor enables H2O2 reduction at a low working potential of 100 mV with a short response time (< 0.1 s). It exhibited a linearity in a wide concentration range from 1-1705 µM. In addition, a long range stability over 3000 s and a very good repeatability is observed, which indicates (Ni, Co)0.85 Se as a potential candidate in electrochemical biosensing.
8:00 PM - BM07.05.08
Dopamine Receptor Conjugated-Nanohybrids Field-Effect Transistor for Discriminating Dopamine Receptor D1 Agonism and Antagonism
Jinyeong Kim1,Oh Seok Kwon1
Korea Research Institute of Bioscience & Biotechnology (KRIBB)1Show Abstract
Screening methodologies of potential G-protein-coupled receptor (GPCRs), which transfer external signals into the cell, drugs has been developed for several decades. Recently, the field-effect transistor (FET) has been used in the development of diagnostic tools, leading to high-performance biosensors, especially liquid-ion gated FET biosensors. Therefore, the FET platform can provide the foundation for the next generation of analytical methods. A principle application of GPCRs is screening new drugs, so the development of a GPCR-conjugated analytical device is highly desired. In this study, we firstly proposed a new approach for studying receptor agonism and antagonism by combining the FET and GPCR roles in a dopamine receptor D1 (DRD1)-conjugated FET system, which is a suitable substitute for conventional cell-based receptor assays. DRD1, for the first time, was reconstituted and purified to mimic native binding pockets that have highly discriminative interaction toward DRD1 agonists/antagonists. The real-time responses from the DRD1-nanohybrid FET were highly sensitive and selective for dopamine agonists/antagonists, and their maximal response levels were clearly different depending on their DRD1 affinities. Moreover, the equilibrium constants (K) were estimated by fitting the response levels. Each K value indicated the variation in the affinity between DRD1 and the agonists/antagonists: greater K value corresponds to a stronger DRD1 affinity in agonism, whereas a lower K value in antagonism indicates a stronger DA-blocking effect.
8:00 PM - BM07.05.09
High-Performance Biosensor Using Multi-Channel System Graphene Field Effect Transistor (GFET) Microfluidics for the Rapid Bacteria Detection
KyungHo Kim1,Oh Seok Kwon1
Korea Research Institute of Bioscience & Biotechnology (KRIBB)1Show Abstract
Over the past of decades, bacteria monitoring is critical in detecting bacteria from contaminated drinking water and food. A various kind of bacteria detection methods such as electrical or optical sensor has been developed. Nevertheless, although many studies with bacteria detection sensors have been reported for high performance detecting properties, the development of the bacteria sensor still remains as challenge. Herein, we study the demonstration of graphene field-effect transistor (GFET) microfluidics using single-layer graphene micropatterns and characterize its monitoring capacity in bacteria detection. The GFET microfluidics had excellent mechanical/ electrical properties in fluidics and showed high sensitivity and selectivity for a target in bacteria mixture. Based on those results, our GFET microfluidics can provide potential applications in the field of disease diagnostics at early stage.
8:00 PM - BM07.05.10
Field Effect Transistor Based In Vitro Dopamine Aptasensor
Jiyeon Lee1,Oh Seok Kwon1
Korea Research Institute of Bioscience and Biotechnology1Show Abstract
In this study, ultrasensitive and precise detection of a representative brain hormone, dopamine was pursued and demonstrated using functional conducting polymer nanotubes modified with aptamer. The produced aptasensor was composed of a micropatterned gold electrode, carboxylated polypyrrole nanotubes, and specific aptamer molecules. The sensor was constructed by sequential deposition of the PPy-COOH nanotubes and aptamer molecules on the electrode. The sensitivity and selectivity of this sensor were monitored using field effect transistor type measurements. In addition, real dopamine released from PC12 and SH-SY5Y cells induced by high concentration potassium ion (K+) stimulus were also analyzed and compared with the data obtained from the sensitivity (1 nM) and selectivity tests. This article can provide the feasibility for practical use of simple and efficient field effect transistor type aptasensor.
8:00 PM - BM07.05.12
Anion-Dependent Doping and Charge Transport in Organic Electrochemical Transistors
Lucas Flagg1,Rajiv Giridharagopal1,David Ginger1
University of Washington1Show Abstract
We study the effects of different dopant anions on mixed ionic/electronic transport in organic electrochemical transistors (OECTs) based on poly(3-hexylthiophene-2,5-diyl) (P3HT). We show that the electronic transport properties depend on the anion present in the electrolyte, with greater transistor currents resulting from the use of polyatomic anions such as such as trifluoromethanesulfonylimide (TFSI) as compared to halide anions. Using spectroelectrochemistry, we show the maximum doping level at a given bias is also anion dependent. Furthermore, we find that the average electronic carrier mobility depends on the identity of the compensating counterion. We investigate this effect further using electrochemical quartz crystal microbalance (EQCM) measurements, showing the solvation shell of the dopant anions within the polymer varies drastically depending on the type of anion. Surprisingly, we find that the doping kinetics in these OECTs is faster for larger anions. Lastly, we use electrochemical strain microscopy (ESM) to resolve ion-dependent differences in local swelling on the nanoscale, providing further insight into the interplay between local polymer structure and ion uptake. These measurements show that the chemical properties of the compensating ion are an important design consideration for polymer materials with mixed ionic/electronic conductor applications.
8:00 PM - BM07.05.13
Liquid-Ion Gated Field-Effect Transistor (FET) with Human Dopamine Receptor Integrated-Multidimensional Conducting Polymer Nanofiber for Dopamine Detection
Oh Seok Kwon1,Seon Joo Park1
Dopamine (DA) has been studied in the field of nervous and cardiovascular systems. Abnormal levels of dopamine is an indicator of neurological disorders, resulting in Alzheimer's and Parkinson's diseases. Therefore, dopamine is a clinically useful diagnostic sign and requires a novel approach with high sensitivity, selectivity and a rapid response. Various sensors have been developed, such as high-performance liquid chromatography (HPLC), mass spectroscopy, and spectrophotometry. However, they are limited by their high cost, low sensitivity, and variable label response.
The field-effect transistor (FET) has been used in the development of diagnosis for several decades. It is gated by changes of charge carrier density in the channel induced by the binding of target molecules, leading to high-performance biosensors. In addition, the FET platform has attracted due to their low cost, easy operation, fast response, label-free operation, parallel sensing as well as high sensitivity.
In this article, we introduced a high performance dopamine sensor based on FET assay. Multidimensional carboxylated poly(3,4-ethylenedioxythiophene) (MCPEDOT) NFs membrane was utilized as the conductive channel of sensor in the FET system. Interestingly, it provided high performance sensing due to enhanced interaction from high surface area and gate-potential modulators. Moreover, hDRD1, G protein-coupled receptors (GPCRs) as the recognition elements, was first expressed in Escherichia coli and modified with the surface of MCPEDOT NFs, leading to high selectivity. As a results, the hDRD1−MCPEDOT NF-based FET exhibits a rapid real-time response (<2 s) with high dopamine selectivity and sensitivity performance (approximately 100 fM).
8:00 PM - BM07.05.14
Nanobioelectronic Nose with Human Olfactory Receptor-Functionalized Graphene Micropatterns for the Analysis of the Spoiled Odor, Trimethylamine
Sung Eun Seo1,Oh Seok Kwon1
Korea Research Institute of Bioscience and Biotechnology1Show Abstract
Trimethylamine(TMA), a odor from the spoiled meat, is a positive proof that we can decide if the food is spoiled or not. We demonstrated the nanobioelectronic nose using the human olfactory receptor(hOR) funtionalized graphene field-effect transistor (GFET). At first, the hOR is prepared from the Escherichia coli (E. coli) for the sensing of the real food sample’s TMA. The nanobioelectronic nose was characterized by SEM, TEM, I-V and transfer curve. The real-time responses under liquid-ion gated system showed that the bioelectronics nose with hOR-conjugated GFET had higher selectivity and specificity compared to conventional electronic noses without bio-receptors. Moreover, the nanobioelectronic nose could provide the effective criteria to judge the food’s freshness. The most advantage of this research is the quantitative analysis of the popular fish. Moreover, it can be utilized to any other real food samples with only the reactive receptor.
8:00 PM - BM07.05.15
High Molecular Density Bio-Electronic Sensor Based on 2D Crystalline Interface and QTY Modified GPCR Proteins
Rui Qing1,Andreas Breitwieser2,Giovanni Azzellino1,Mantian Xue1,Jiayuan Zhao1,Uwe Sleytr2,Jing Kong1,Shuguang Zhang1
Massachusetts Institute of Technology1,University of Natural Resources and Life Sciences Vienna2Show Abstract
Bio-electronic is an emerging antidisplinary subject which utilizes biomolecules in electronics or mimics biological architectures. One important aspect of the field is to fabricate sensors for biomolecules detection, i.e. ligands. Researchers previously designed sensors based on metal-oxide-semiconductor (MOSFET), polymers and inorganic crystalline materials which produce decent sensitivity but lacks selectivity. Recent efforts are devoted on directly connecting biological receptors with electronic systems. G protein-coupled receptors (GPCR), are the largest family of membrane receptors that detects information (molecules and lights) and transduce to cell internal signals to regulate body functions. There are nearly 1000 types of GPCR proteins in human body, each one being highly specific to a particular signal, which make them suitable candidates as sensors in bio-electronic devices.
Based on our previous reported novel approach of QTY modification on GPCR proteins, we were able to obtain water soluble receptors active to their natural ligands without adding any detergent. Recombinant SbpA S-layer proteins can reproduce ordered 2-dimensional crystalline monolayer in vivo and were employed as the intermediate layer between biomolecules and electronic substrates. By fusing –Fc region of human IGg protein to GPCRQTY and Protein GG onto SbpA, we successfully formed GPCR-S-layer complex and anchor them onto the electronic active surface, i.e. Si wafer, graphene, etc. SbpA proteins also helped to guide the orientation of attached GPCRQTY proteins and expose their active binding sites. The assembly yields functional molecule monolayer density as high as 2.37-4.73*1012 molecule/cm2. Binding/Elution of the GPCRQTY proteins on the intermediate layer can be regulated by environmental pH. The bioelectronics platform yields detectable electrical and electrochemical signal in response to the biological stimulus from the receptor layer. Coupled with different types of receptor proteins this approach can prove to be a universal platform for bioelectronics and nano-sensing systems.
8:00 PM - BM07.05.16
The Charge Carrier Modulation in PEDOT:PSS Films via Chemical Crosslinking with PVA
Ji Hwan Kim1,Myung-Han Yoon1
Gwangju Institute of Science & Technology (GIST)1Show Abstract
Recently, the charge carrier modulation in semiconducting polymer films has drawn much attention, but there exist a relatively small number of studies on the charge carrier modulation in highly conductive polymer films despite their potential for energy storage and bioelectronics applications. In this work, we report the charge carrier modulation of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films and its application to organic electrochemical transistors (OECTs) with finely-tuned threshold voltage characteristics by crosslinking with polyvinyl alcohol (PVA) as a de-dopant. PVA was blended with an aqueous solution of PEDOT:PSS and the PEDOT:PSS-PVA blend films were chemically crosslinked in the solid state. The electrical characterization revealed that the crosslinking with PVA significantly lowered the conductivity from 1800 to 80 S/cm, the volumetric capacitance form 100 to 1 F/cm3, and the hole concentration from 3.3 × 1019 to 7.5 × 1017 /cm3 in the PEDOT:PSS-PVA hybrid films. Despite the inclusion of electrically insulating polymer in the conductive material, however, the resultant OECT devices exhibited relatively high on-current (~1 mA), large current on/off ratio (>103), and excellent transconductance (>2 mS), which are acceptable for bioelectronic sensors with the customized electrical/electrochemical properties. In addition, the concurrent threshold voltage shift from 0.5 to 0.3 V upon PVA crosslinking suggests that the PEDOT:PSS-PVA hybrid channel can offer finely tunable threshold voltage characteristics to OECT devices without the significant degradation in OECT performance.
8:00 PM - BM07.05.18
Highly Sensitive Lactate Sensors Based on Carbon MEMS (CMEMS)
Shahrzad Forouzanfar1,Chunlei Wang1,Nezih Pala1
Florida International University1Show Abstract
L-Lactic acid is one of the important metabolites produced during the anaerobic phase of glycolysis, making its precise determination highly important in various fields such as clinical diagnosis, sport, and military activities. Lactate plays a crucial role in several areas of human health, including heart failure, hepatic dysfunction, shock, respiratory insufficiency and systemic disorders. In sports medicine, knowledge of optimal blood lactate levels is vital to ensuring the maximum performance of an athlete during intensive exercise and endurance-based activities.
Various methods have been developed for determining lactate levels, such as optical, nuclear magnetic resonance, liquid chromatography, fluorimetry, and amperometry. Among these methods, electrochemical ones possess advantages such as simple instrumentation, low detection limit, and wide dynamic range, as well as high selectivity and stability. A Carbon-microelectromechanical system (C-MEMS) is one in which Carbon is synthesized through pyrolysis of micro patterned photoresist polymer in an oxygen-free environment under high temperatures. Carbon possesses various remarkable properties such as a wide electrochemical window, low non-specific adsorption of biomolecules, excellent biocompatibility, and low cost. Furthermore, carbon-based materials exhibit good electrical conductivity, as well as good tolerance toward bio-fouling. The surface of the carbon can be functionalized efficiently via various physical, chemical, or electrochemical treatments. C-MEMS devices circumvent the major drawbacks associated with commercialized screen-printed carbon electrodes such as low resolution and miniaturization.
We developed an electrochemical C-MEMS-based sensing platform to detect L-Lactic Acid. The sensing platform of the biosensor—interdigitated carbon micro fingers—was synthesized by pyrolyzation of photo-patterned photoresist polymer in oxygen-free and high-temperature conditions. The surfaces of the fingers were functionalized by an oxidation pretreatment technique involving oxygen reactive ion etching (RIE) to form –COOH on glassy carbon. Taking advantage of having high concentrations of this carboxylic group on the surface of the carbon, we immobilized Lactate Oxidase (LOx) on the surfaces of the interdigitated carbon micro fingers without any other surface pretreatments. We employed various analytical characterization methods such as Fourier-transform infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) for material characterization. Sensing capabilities were measured by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS). The carbon capacitive sensor demonstrated detection of lactate over a wide dynamic range of 50 nM-5 mM for the electrode area of 0.5×0.5 cm2. The sensitivity of this linker-free lactate sensor was found to be 40 nM /cm2, making it the first carbon capacitive L-lactate sensor with such high sensitivity.
8:00 PM - BM07.05.19
Detection of Hormone Using a Reagent-Free Electrochemical Method
Bo Wu1,Ye Liu1,Amritha Ajithkumar1,Yi-Chieh Wang1,Akash Kannegulla1,Li-Jing Larry Cheng1
Oregon State University1Show Abstract
We report a bioresponsive electrode to achieve reagent-free electrochemical detection of hormone cortisol. The sensor combines a molecularly-imprinted polymer (MIP) layer that enables selective binding of target cortisol and a ferrocene-decorated polymer layer that offers charge transfer to amplify the detection signal readout in cyclic voltammetry (CV) measurements. Conventional CV-based biosensing requires the introduction of redox reagents, such as ferrocyanide, in analyte solutions to identify the docking of target molecules on the electrode surface. The composite enhances detection signal by offering redox peaks in CV characteristics without adding redox reporters in the analyte which simplifies the workflow to allow real-time detection. The measurement result shows that the current level decreases with the increase of cortisol concentration. The trend stems from the fact that the binding of cortisol in MIP hinders the charge transfer at the electrode-solution interface. The sensor exhibits a large dynamic range up to micromolar concentration and has a detection limit of less than 10 pM, sufficient for the application of salivary cortisol measurement.
8:00 PM - BM07.05.20
Hydrogel-Gate Field-Effect Transistors for Multiplex Biosensing
Richard Vo1,Hamed Bay1,Huan-Hsuan Hsu1,Siran Cao1,Zhiming Mo1,Xiaocheng Jiang1
Tufts University1Show Abstract
Nanoscale field-effect transistors (FETs) represent a unique platform for real-time, label-free transduction of biochemical signals with unprecedented sensitivity and spatiotemporal resolution, yet their translation toward practical biomedical applications remains a challenge. Problems such as Debye screening of charge-based signals in high-ionic strength environments, non-specific binding of background biomolecules,and poor life-time have limited their applications in physiologically relevant conditions. Herein we demonstrate the potential to overcome these key limitations by exploiting molecularly encoded functional hydrogel as the gate material. Spatially-defined photopolymerization is utilized to achieve selective patterning of hydrogel on top of individual graphene FET devices with diffraction-limited spatial resolution. Combined with on-chip microfluidic control, bio-specific receptors can be sequentially encapsulated into the hydrogel gate to independently encode selectivity in FET device arrays. The hydrogel-mediated integration of penicillinase, for example, has been demonstrated to effectively catalyze enzymatic reaction in the confined FET microenvironment, enabling real-time, label-free detection of penicillin down to 0.2 mM. When additional enzymes (such as urease and acetylcholinesterase) are incorporated into adjacent devices, highly specific and localized signals can be recorded with minimal cross-talk, thus demonstrating the unique potential of the current strategy in high spatial resolution multiplex sensing. In addition, the passivation of the graphene FET device with a hydrogel layer is found to significantly reduce the nonspecific signal. In a control experiment with 1 mg/ml bovine serum albumin solution, bare graphene devices showed a 5 mV signal, which is inhibited for hydrogel-gate FETs, thereby displaying the possibility for applications in unprocessed physiological fluids. Lastly, longitudinal measurements of hydrogel FET performance show a significant improvement in device lifetime and in maintaining a similar signal amplitude. Hydrogel-gate FETs maintain a signal of 50 mV for up to 7 days. In comparison, devices with free or conjugated enzymes show a 70% signal loss after 4 hours. The current work represents a strategic approach to enable the application of existing nanoelectronic tool sets in physiologically relevant conditions and has potential for use in real time point-of-care diagnostics and in vivo monitoring of disease progression through long-term tissue interfacing applications.