Jianhua Hao, The Hong Kong Polytechnic University
Sohini Kar-Narayan, University of Cambridge
Caofeng Pan, Chinese Academy of Sciences
Xudong Wang, University of Wisconsin--Madison
JPhys Energy | IOP Publishing
ES21.01: Piezoelectric and Triboelectric Nanogenerators I
Tuesday AM, April 23, 2019
PCC North, 100 Level, Room 132 C
10:30 AM - *ES21.01.01
Piezotronics and Piezo-Phototronics of theThird Generation of Semiconductors
Zhong Lin Wang1,2
Georgia Institute of Technology1,Beijing Institute of Nanoenergy and Nanosystems, CAS2Show Abstract
Piezoelectricity, a phenomenon known for centuries, is an effect that is about the production of electrical potential in a substance as the pressure on it changes. For wurtzite structures such as ZnO, GaN, InN and ZnS, due to the polarization of ions in a crystal that has non-central symmetry, a piezoelectric potential (piezopotential) is created in the crystal by applying a stress. The effect of piezopotential to the transport behavior of charge carriers is significant due to their multiple functionalities of piezoelectricity, semiconductor and photon excitation. By utilizing the advantages offered by these properties, a few new fields have been created. Electronics fabricated by using inner-crystal piezopotential as a “gate” voltage to tune/control the charge transport behavior is named piezotronics, with applications in strain/force/pressure triggered/controlled electronic devices, sensors and logic units. This effect was also extended to 2D materials such as MoS2. Piezo-phototronic effect is a result of three-way coupling among piezoelectricity, photonic excitation and semiconductor transport, which allows tuning and controlling of electro-optical processes by strain induced piezopotential. The objective of this talk is to introduce the fundamentals of piezotronics and piezo-phototronics and to give an updated progress about their applications in energy science (LED, solar) and sensors (photon detector and human-CMOS interfacing).
.Z. Wu, X.N. Wen, Z.L. Wang “Pixel-addressable matrix of vertical-nanowire piezotronic transistors for active/adaptive tactile imaging”, Science, 340 (2013) 952-957.
.F. Pan, L. Dong, G. Zhu, S. Niu, R.M. Yu, Q. Yang, Y. Liu, Z.L. Wang* “Micrometer-resolution electroluminescence parallel-imaging of pressure distribution using piezoelectric nanowire-LED array”, Nature Photonics, 7 (2013) 752-758.
Z.L. Wang “Piezopotential Gated Nanowire Devices: Piezotronics and Piezo-phototronics”, Nano Today, 5 (2010) 540-552.
 Q. Yang, W.H. Wang, S. Xu and Z.L. Wang* “Enhancing light emission of ZnO microwire-based diodes by piezo-phototronic effect”, Nano Letters, 11 (2011) 4012–4017.
 W.Z. Wu, L. Wang, Y.L. Li, F. Zhang, L. Lin, S. Niu, D. Chenet, X. Zhang, Y. Hao, T.F. Heinz, J. Hone, and Z.L. Wang “Piezoelectricity of single-atomic-layer MoS2 for energy conversion and piezotronics", Nature, 514 (2014) 470-474.
 W.Z. Wu and Z.L. Wang “Piezotronics and piezo-phototronics for smart adaptive electronics and optoelectronics”, Nature Review Materials, 1 (2016) 16031 doi:10.1038/natrevmats.2016.31.
11:00 AM - *ES21.01.02
Sustainable Power Generation from Multifunctional Triboelectric Nanogenerators
Sungkyunkwan University1Show Abstract
Energy harvesting systems based on triboelectric nanomaterials are in great demand, as they can provide routes for the development of self-powered devices which are highly flexible, stretchable, mechanically durable, and can be used in a wide range of applications. Our recent research interest mainly focuses on the fabrication of high-performance triboelectric nanogenerators (TENGs) based on various kinds of nanomaterials. Flexible TENGs exhibit good performances and are easy to integrate which make it the perfect candidate for many applications, and therefore crucial to develop. In this presentation, I firstly introduce the fundamentals and possible device applications of TENGs, including their basic operation modes. Then the different improvement parameters will be discussed. As main topics, I will present a couple of recent achievements regarding highly stretchable transparent flexible TENGs, textile-based wearable TENGs, highly robust and efficient TENGs with multifunctional materials, etc. The recent research and design efforts for enhancing power generation performance of TENGs to realize self powering of portable and wearable sensors and electronics will also be discussed in this talk. Finally I am going to introduce a graphene tribotronic touch sensor which is based on coplanar coupling of a single electrode mode TENG (S-TENG) and a graphene FET. When any object (e.g. human finger) comes into contact with friction layer of the S-TENG, the charges are produced due to well-known triboelectric effect. The triboelectric charges act as a gate bias to the graphene FET and modulates its current transport. The tribotronic sensors have displayed a sensitivity of ~2% kPa-1, a limit of detection <1 kPa, and a response time of ~30 ms. Furthermore, the devices can effectively detect touch stimuli from both bare and gloved fingers which can be a limitation with capacitive touch screens.
11:30 AM - *ES21.01.03
Theoretical Potential for Low Energy Consumption Phase Change Memory Utilizing Electrostatically-Induced Structural Phase Transitions in 2D Materials
Evan Reed1,Daniel Rehn1,Yao Li1,Eric Pop1
Stanford University1Show Abstract
Structural phase-change materials are of great importance for applications in information storage devices. Thermally driven structural phase transitions are employed in phase-change memory to achieve lower programming voltages and potentially lower energy consumption than mainstream nonvolatile memory technologies. However, the waste heat generated by such thermal mechanisms is often not optimized and could present a limiting factor to widespread use. The potential for electrostatically driven structural phase transitions has recently been predicted and subsequently reported in some two-dimensional materials, providing an athermal mechanism to dynamically control properties of these materials in a nonvolatile fashion while achieving potentially lower energy consumption. In this work, we employ DFT-based calculations to make theoretical comparisons of the energy required to drive electrostatically-induced and thermally-induced phase transitions. Determining theoretical limits in monolayer MoTe2 and thin films of Ge2Sb2Te5, we find that the energy consumption per unit volume of the electrostatically driven phase transition in monolayer MoTe2 at room temperature is 9% of the adiabatic lower limit of the thermally driven phase transition in Ge2Sb2Te5. Furthermore, experimentally reported phase change energy consumption of Ge2Sb2Te5 is 100–10,000 times larger than the adiabatic lower limit due to waste heat flow out of the material, leaving the possibility for energy consumption in monolayer MoTe2-based devices to be orders of magnitude smaller than Ge2Sb2Te5-based devices.
ES21.02: Piezotronics I
Tuesday PM, April 23, 2019
PCC North, 100 Level, Room 132 C
1:30 PM - *ES21.02.01
Controlling Polar Domains on Oxide Surfaces to Optimize Photochemical Reactivity
Gregory Rohrer1,Paul Salvador1,Wenjia Song1,Ajay Pisat1,Mingyi Zhang1
Carnegie Mellon University1Show Abstract
For many years, researchers have sought metal oxide catalysts that efficiently split water in sunlight to produce hydrogen fuel. On the surfaces of oxide semiconductors with polar domains, electrons are attracted to positively terminated domains where they promote reduction reactions and holes are attracted to negatively charged domains where they promote oxidation. The separation of charge carriers reduces charge carrier recombination and the back reaction of the reduced and oxidized products. Charged domains can arise at the surfaces because of piezoelectricity, flexoelectricity, or differences in the chemical termination of the surface. Here, we report results showing that it is possible to optimize the overall photochemical reactivity of SrTiO3 and BaTiO3 by controlling relative areas of the polar surface regions and the surface charge through solution pH. For SrTiO3, the fraction of the surface terminated by positive or negative charges is controlled through thermochemical treatments. For BaTiO3, domain orientations are altered by controlling the cooling rate. The solution pH can then be used to 'tune' the surface potential to a point where the photoanodic and photocathodic reactions occur at maximum and equal rates, which is the point of optimized reactivity.
2:00 PM - ES21.02.02
Impedance Tomography Mapping and Data Analytics Based Characterization of Non-Thermal Plasma Assisted Surface Modification of Piezoelectric and Multifunctional ZnO and BaTiO3 Based Electro-Active Thin Films
Yuanyuan Xie1,Walker Tuff1,Saquib Ahmed2,Sankha Banerjee1
California State University, Fresno1,Buffalo State College2Show Abstract
Electrical impedance spectroscopy (EIS) has been recognized as a powerful diagnostic tool for its extraordinary sensitivity. It has been widely used in evaluating electrical properties of materials and their interfaces with surface-modified techniques. Typically, EIS test applies a harmonic voltage perturbation to the target, then measures the response current, which can yield invaluable information of material electrical properties and structures as so-called Impedance spectroscopy. In practical, impedance spectroscopy measurement on a multiphasic / multifunctional electro-active composite material is conducted through probing two electrodes at specified point or surface, while the specification of probing sites is generally arbitrary. The following work deals with the impedance tomography based characterization of ZnO/ZnO naowire-Epoxy-BaTiO3 thin films with a variation in ZnO volume fraction from 1-10%. Impedance tomography data will also be used for generating dependent and independent data sets towards data analytics based optimization of surface properties and development of fabrication-processing-property relationships. The surface micro-structure and topography will analyzed using scanning electron microscopy and profilometry. The piezoelectric and dielectric properties of these composites will also be characterized.
2:15 PM - *ES21.02.03
Piezotronic/Piezophototronic Based Sensors and Applications
Beijing Institute of Nanoenergy and Nanosystems, CAS1,Guangxi University2Show Abstract
Multifunctional micro/nano devices and systems are of important applications in smart electronics for health care, human-machine interfacing, infrastructure monitoring and security. In recent years, piezophototronic effect is developed fast since it offers a new method to improve/tune the optoelectronic properties dramatically. The key characteristic of the piezotronic/piezo-phototronic effect is that the carrier generation, transport, separation and/or recombination at the heterojunction/interface can be tuned by modulating the piezopotential which created and further tuned by externally applied strain.
Piezophototronic effect can enhance the sensitivity of photodetector dramatically. Here, we show a self-powered GaN flexible film-based metal-semiconductor-metal (MSM) UV photoswitch. The asymmetric MSM structure was designed to suppress carrier recombination and enhance carrier transport. At self-powered condition (no external bias voltage), its UV on/off ratio reaches up to 4.67*105 with high reliability of on/off switching response. Also its UV detection shows an excellent sensitivity (1.78*1012 cmHz0.5W-1). In particular, strain modulation can improve the UV on/off ratio (~154%) by piezo-phototronic effect.
Besides photoelectric conversion and electroluminescence, photoluminescence can be tuned by piezoelectric charge as well. Here have developed a new method of pressure sensing by using pressure/strain induced piezoelectric charge to tune PL intensity of InGaN/GaN MQW under small strain (0~0.15 %). Such modulation effect is distinct, linear and ultrafast. Based upon it, an all optical pressure sensor array by the piezo-phototronic effect has been developed to measure dynamic pressure distribution without the need of electricity. Beyond the limitations of electrical connection, our all-optical device offers a novel and suitable way for large-area, high-uniform, high resolution, ultrahigh speed pressure/strain distribution sensing.
When combine piezotronic effect with magnetostriction, multi-field couplings can be realized. For example, magneto-optics and electro-optics, magneto-electrics and magneto-mechanics, piezotronics and piezophototronics, which could be of interest for fabricating functional devices in the fields of energy conversion, magnetic/optical imaging, high-density optical communication and information storage, smart sensing, and so on.
2:45 PM - ES21.02.04
Piezo-Phototronic Effect in GaN Based Optoelectronic Devices
Beijing Institute of Nanoenergy and Nanosystems1Show Abstract
As the third-generation semiconductors, III-Nitrides exhibits great potentials in the solid-state lighting, display, power device, photovoltaics and so on. The piezoelectric property is the great difference between III-Nitrides and previous semiconductors (Silicon, Germanium, etc.). Prof. Wang pointed it out that the piezo-potential can be used as a gate to tune/control the carrier generation, transport, separation and/or recombination via external strain, and thus tuning the device performances .
This report focuses on piezo-phototronic effects in III-nitrides. Firstly, in the framework of the quantum perturbation theory and constitutive equations, we proposed a self-consistent model to study the piezo-phototronic effects in quantum structure [2,3]. This model matches well with the optical excitation in InGaN/GaN quantum well under the various external stress field. Furthermore, we studied the carrier dynamic process in piezo-phototronic effects with the transit piezo-phototronic model and the time-resolved photoluminescence for the first time. The piezoelectric field was partly “canceled”, which increased the overlap of wavefunctions to decrease the carrier decay time. Thus, the maximum speed of a single chip was increased from 54 MHz up to 117 MHz in a blue LED chip under 0.14% compressive strain. Finally, the piezo-phototronic effect was used to effectively improve the conversion efficiency of InGaN/GaN quantum well and compensated the thermal degradation in high power InGaN/GaN micro-strip LED arrays [4,5]. These researches deepen our understanding on carrier’s excitation and transportation under external strain filed, and exhibits important applications in communication, lighting and energy collections.
1.X. Wang, J. Song, J. Liu, Z. L. Wang, Science 2007, 316 ,102
2.Xin Huang, Chunhua Du, Yongli Zhou, Chunyan Jiang, Xiong Pu, Wei Liu, Weiguo Hu*, Hong Chen*, and Zhong Lin Wang*, ACS Nano 2016 10 (5), 5145-5152
3.Xin Huang, Chunyan Jiang, Chunhua Du, Liang Jing, Mengmeng Liu, Weiguo Hu*, and Zhong Lin Wang*, ACS Nano 10 (12), 11420-11427, 2016
4.Chunyan Jiang, Liang Jing, Xin Huang, Mengmeng Liu, Chunhua Du, Ting Liu, Xiong Pu, Weiguo Hu* and Zhong Lin Wang*, ACS Nano 11 (9), 9405–9412, (2017)
5.Chunhua Du, Liang Jing, Chunyan Jiang, Ting Liu, Xiong Pu, Jiangman Sun, Dabing Li* and Weiguo Hu*, Materials Horizons, DOI 10.1039/C7MH00876G
ES21.03: Piezoelectric and Triboelectric Nanogenerators II
Tuesday PM, April 23, 2019
PCC North, 100 Level, Room 132 C
3:30 PM - *ES21.03.01
Rational Materials Design for High-Output Triboelectric Nanogenerator
Jeong Min Baik1
Ulsan National Institute of Science and Technology1Show Abstract
Dielectric materials, commonly referred to as electrical insulators, have received much attention owing to their strong electron bonding, good support of electric fields, and low energy loss. In particular, polarization and depolarization that occur in dielectrics as a result of an external electric field has been investigated as a means to efficiently charge and discharge electricity, which are very useful when applied to capacitors. Dielectrics have also been widely used as charge accepting materials in triboelectric nanogenerator (TENG). So far, various dielectric materials such as polydimethylsiloxane (PDMS), poly(methyl methacrylate) (PMMA), polyimide (PI), polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE) have been used without any modifications and the electrical signals were not enough. Very recently, the modification of properties such as compressibility surface potential, and hydrophobicity in a few TENGs has been reported, however, most of them have focused on partial reports on the effects of the output performance. Here, we present rational design of effective polymer dielectrics for high-output triboelectric nanogenerator based on PDMS, PI, and PVDF. The stretchable materials as positive charged materials were also presented. This will make the TENG generate higher output power, compared with the PTFE-based TENG.
4:00 PM - ES21.03.02
Exceptional Piezoresponse of Zinc-Oxide Nanosheets Grown via Ionic Layer Epitaxy for Next-Generation Piezotronics
Carlos Corey1,Xin Yin1,Xudong Wang1
University of Wisconsin–Madison1Show Abstract
Piezotronics is a promising new class of semiconductor-devices that offer important implications for the realization of flexible nano-electronic, nano-sensor, and microelectromechanical (MEMS) applications. However, reproducibility in both synthesis and sensitivity has been a materials challenge for achieving wide-scale adaptation of these applications. We present a novel method for the synthesis and study of the piezoelectric effect of single-crystalline zinc oxide (ZnO) nanosheets (NS). Here we show reliable synthesis of free-standing two-dimensional (2D) nanometer thick ZnO achieved using Ionic Layer Epitaxy (ILE). In this method, a highly-packed surfactant monolayer guides crystal evolution underneath the ionized headgroups at the air-water interface. Using dynamic contact electrostatic force microscopy (DC-EFM) we measure the piezo response coefficient (d33) of our as-synthesized NSs in the nanometer scale from 1 to 3 nm. The d33 was found in the range of 10-60 pm/V. The thickness-related piezoelectric responses were studied as well. Comparing to reported piezo response values of bulk ZnO, the piezo response of our ZnO NSs offer significant implications for next-generation nanomaterials as building blocks for piezotronics.
4:15 PM - *ES21.03.03
Stretchable and Wearable Triboelectric Nanogenerators for Human Machine Interface
Pooi See Lee1
Nanyang Technological University1Show Abstract
Harvesting energy from our environment or biomechanical motion requires the development of mechanical energy harvesting devices that are compliant to curvilinear surfaces or wearable on human body. Triboelectric nanogenerators (TENGs) generate electricity by triboelectrification and electrostatic induction from ambient energy that are ubiquitous and constantly available. Wearable TENGs based on textiles are attractive options as it can be incorporated onto garments and versatile for high portability. We developed two kinds of textile-TENGs, one for harvesting energy from water flow and another for harvesting biomechanical energy from human motion. A wearable all-fabric-based TENGs with self-cleaning and antifouling properties can be realized with the use of hydrophobic cellulose oleoyl ester nanoparticles (HCOENPs), a low-cost and nontoxic coating material to achieve superhydrophobic coating. An all-fabric-based dual-mode device harvests both the electrostatic energy and mechanical energy of water, achieving the maximum instantaneous output power density of 0.30 W m-2. To generate energy from subtle biomechanical motion, an all-textile nanogenerator utilizing HCOENPs encapsulated black phosphorus was presented with considerably high output (~250–880 V, ~0.48–1.1 μA cm−2) with a small force (~5 N) and low frequency (~4 Hz), which can power small electronic gadgets. On the other hand, ionic based materials can be utilized to generate signal from touch and decode environmental changes. Based on the ionic conductive material, a stretchable, transparent and self-healable nanogenerator has been developed. To realize an extremely stretchable and self-healable device, we designed a thermoplastic elastomer that is 3D printable and it can serve as the triboelectric active layer and simultaneously as the matrix for current collector. This optimized elasmomer leads to enhanced interface compatibility that harnesses the outstanding output performance.
Jianhua Hao, The Hong Kong Polytechnic University
Sohini Kar-Narayan, University of Cambridge
Caofeng Pan, Chinese Academy of Sciences
Xudong Wang, University of Wisconsin--Madison
JPhys Energy | IOP Publishing
ES21.04: Piezoelectric and Triboelectric Nanogenerators III
Wednesday AM, April 24, 2019
PCC North, 100 Level, Room 132 C
8:00 AM - ES21.04.01
Large-Area Solution-Grown Two-Dimensional Tellurene for Smart, Ubiquitous Electronics
Yixiu Wang1,Gang Qiu1,Ruoxing Wang1,Peide Ye1,Wenzhuo Wu1
Purdue University1Show Abstract
The reliable production of two-dimensional (2D) crystals are essential for exploring new science and implementing novel technologies in the 2D limit. However, ongoing efforts are limited by the vague potential in scaling-up, restrictions in growth substrates and conditions, small sizes and/or instability of synthesized materials. Here we report the fabrication of large-area, high-quality 2D tellurene by a substrate-free solution process. The crystals exhibit process-tunable thicknesses from a monolayer to tens of nanometers, and lateral sizes up to 100 um. The chiral structure of tellurene gives rise to strong in-plane anisotropic properties and giant thickness-dependent shifts in Raman vibrational modes, unseen in 2D layered materials. The tellurene transistors can exhibit air-stable performance at room temperature for over two months, with on/off ratios on the order of 106 and field-effect mobility ~700 cm2/Vs. More strikingly, with scaled channel length and integration with high-k dielectrics, the record-high on-state current density of 1.06 A/mm is demonstrated, surpassing all state-of-the-art 2D-based transistors. Our versatile solution process allows access to a broad range of characterization and application of tellurene as a new 2D semiconductor for high-performance, energy-efficient electronics in future ubiquitous applications.
1. Wang, Y. X., Qiu, G., Wang, R. X., Huang, S. Y., Wang, Q. X., Liu, Y. Y., Du, Y. C., Goddard, W. A., Kim, M. J., Xu, X. F., Ye, P. D., Wu, W. Z., “Field-effect transistors made from solution-grown two-dimensional tellurene”, Nature Electronics, 2018, 1, 228-236.
2. Wu, W. Z., Qiu, G., Wang, Y. X., Wang, R. X., Ye, P. D., “Tellurene: its physical properties, scalable nanomanufacturing, and device applications”, Chem. Soc. Rev., 2018, 47, 7203-7212.
3. Qiu, G., Wang, Y. X., Nie, Y. F., Zheng, Y. P., Cho, K., Wu, W. Z., Ye, P. D., “Quantum transport and band structure evolution high magnetic field in few-layer tellurene”, Nano Letters, 2018, 18, 5760-5767.
4. Jin S. Y., Wang, Y. X., Motlag, M., Gao, S. J., Xu, J., Nian, Q., Wu, W. Z., Cheng, G. J., “Large area direct laser shock imprinting of 3D biomimic hierarchical metal surface for triboelectric nanogenerator”, Adv. Mater., 2018, 30 (11), 1705840.
5. Gao, S. J., Wang, Y. X., Wang, R. X., Wu, W. Z., “Piezotronic effect in 1D van der Waals solid of elemental tellurium nanobelt for smart adaptive electronics", Semicond. Sci. Technol., 2017, 32, 104004.
6. Du, Y., Qiu, G., Wang, Y. X., Si, M., Xu, X., Wu, W. Z., Ye, P. D., “One-dimensional van der Waals material tellurium: Raman spectroscopy under strain and magneto-transport”, Nano Lett., 2017, 17 (6), 3965-3973.
8:15 AM - *ES21.04.02
Conformal Piezoelectric Energy Harvesting and Storage from Motions of Internal Organs
Massachusetts Institute of Technology1Show Abstract
Implantable medical devices have made a major impact in improving healthcare. In recent years, these devices have increasingly become active rather than passive – for example, cardiac pacemakers are those of the active type. A key challenge for these active systems is their need for an internal electrical power source. A downside of present active systems is the limitation of their internal batteries, which are rigid, bulky and must be changed frequently, thus requiring recurring surgical procedures, with associated complication risks and additional healthcare costs. One compelling solution would be to employ energy harvesting as a means of recharging or completely replacing batteries for active implantable medical devices. Energy harvesting — through chemical reactions, heat extraction, blood flow, and natural mechanical movements of organs — could help address energy depletion issues in implantable devices. However, most energy harvesting units being considered today are like conventional batteries, in that they also rely on rigid electronics and subcomponents, and therefore, are incapable of providing intimate mechanical contact with soft tissue.
We have developed a new class of biocompatible piezoelectric mechanical energy harvesters (PZT MEHs) that are soft and flexible, with extremely low bending stiffness, allowing them to conform to and laminate on the heart as well as on other soft tissues. These devices are the first-of-its-kind flexible generators that convert mechanical energy from internal organ movements into electric energy to power medical devices. We designed and fabricated the entire device, and performed in vitro and in vivo tests, and analyzed the data to show that it is a feasible new invention. The co-integrated collection of such energy-harvesting elements with rectifiers and microbatteries provides an entire flexible system, capable of viable integration with the beating heart via medical sutures and operation with efficiencies of ∼2%.
This conformal mechanical energy harvesters can yield significant amounts of electrical power from motions of internal organs, up to and exceeding levels relevant for practical use in implants. Under the rhythmic contraction of the heart muscle, the device bends and relaxes, enabling to supply enough trickle charge — a steady stream of charging current at low rate — to satisfy the needs of a pacemaker. Thus, this technology could extend the battery life of implanted medical devices or even eliminate the need of battery replacement that altogether would spare patients from repeated operations and the risk of surgical complications. Another potential application of this technology is in powering health monitors/sensors worn epidermally on skin.
8:45 AM - ES21.04.03
Fibre-Based Triboelectric Generators for Smart Textiles Using Surface-Modified Electrospun Polymer Fibres
Tommaso Busolo1,Daniel Ura1,Sung Kyun Kim2,Piotr Szewczyk1,Mateusz Marzec1,Andrzej Bernasik1,Urszula Stachewicz1,Sohini Kar-Narayan2
AGH University of Science and Technology1,University of Cambridge2Show Abstract
Wearable healthcare devices and point-of-care diagnostics are essential tools to provide affordable healthcare globally and to deliver personalised medicine. These devices are able to remotely monitor patient health in real time, thus improving diseases management and reducing medical cost. Furthermore, the physiological data collected can be used by a machine learning software to provide personalised treatments.
One of the biggest challenges that wearable technology faces is power supply. In this context, triboelectric generators are promising as they rely on motion-generated surface charge transfer between materials with different electron affinities to convert mechanical energy, for example from body movements, into useful electricity. Fibre-based triboelectric generators are therefore particularly promising for wearable applications as they can harvest the kinetic energy from body motion and be seamlessly integrated into “smart” textiles at the same time. Current fibre-based triboelectric generators are limited by low power output. Two of the most effective methods to improve this are increasing surface area and altering the surface chemistry of the material. Higher surface area allows for higher charge transfer density, while tailored surface charge properties improve the charge transfer mechanisms.
Electrospinning can be used to effectively tailor the surface chemistry of fibres by alternating voltage polarities in a single-step manufacturing process. In our work, we have enhanced the triboelectric performance of poly(methyl methacrylate) and polyvinylidene fluoride by engineering both its surface area (due to the fibre geometry) as well as the surface chemistry (by controlling the polarity of applied voltage during electrospinning). Scanning electron microscopy and electrical measurements were used to study the effect of surface area enhancement. X-ray photoelectron spectroscopy and Kelvin probe force microscopy have demonstrated that the improvement in triboelectric output is correlated to molecular reorientation on the fibre surface caused by the applied voltage during electrospinning. The suitability of surface-modified electrospun fibres as high-performance materials for fibre-based triboelectric generators is demonstrated in this work, including applications in smart textiles.
 A. Tricoli, N. Nasiri, S. De, Wearable and Miniaturized Sensor Technologies for Personalized and Preventive Medicine, Adv. Funct. Mater. 27 (2017) 1–19. doi:10.1002/adfm.201605271.
 U. Stachewicz, C.A. Stone, C.R. Willis, A.H. Barber, Charge assisted tailoring of chemical functionality at electrospun nanofiber surfaces, J. Mater. Chem. 22 (2012) 22935–22941. doi:10.1039/c2jm33807f.
9:00 AM - *ES21.04.04
Triboelectric Technology Based Sensors for Human-Machine Interaction
Chongqing University1Show Abstract
A sensing system is the core in human machine interaction (HMI), which connects the human being and machine with understanding the human instruction or senses. In this presentation, I will introduce the sensors based on triboelectric nanogenerator (TENG) technology, including an eye motion triggered self-powered mechnosensational communication system (1), a self-powered auditory sensor for social robotics and hearing aids (2), a quantization rotation sensing and gesture control of a robot joint (3), and a self-powered 2D barcode recognition system for personal identification. This work expresses notable advantages of using TENG technology to build a new generation of sensing systems for meeting the challenges in HMI.
 Sci. Adv. 2017; 3: e1700694.
 Sci. Robot. 2018, 3: eaat2516.
 Nano Energy, doi.org/10.1016/j.nanoen.2018.10.044
 Nano Energy 43 (2018) 253–258
ES21.05: Piezotronics II
Wednesday AM, April 24, 2019
PCC North, 100 Level, Room 132 C
10:15 AM - *ES21.05.01
Scalably-Nanomanufactured 2D Tellurene for Ubiquitous Electronics and Smart Sensors
Purdue University1Show Abstract
The reliable production of atomically-thin crystals is essential for exploring new science and implementing novel technologies in the 2D limit. In this talk, I will discuss our recent discovery of a new 2-D material, tellurene, synthesized by a substrate-free solution process. The tellurene crystals exhibit process-tunable thicknesses from a monolayer to tens of nanometers, and lateral sizes ~ 100 um. Our prototypical tellurene transistor device, which is air-stable, shows an excellent all-around figure of merits compared to existing 2D materials. We further carry out the first experimental exploration of piezotronic effect in tellurene and systematically investigate the piezotronic transport properties. The fundamental understanding of piezotronic coupling in tellurene is expected to provide insights for the development of 2-D material piezotronics, leading to the realization of “smarter” electronics for a multitude of emerging technologies, e.g., wearable electronics, soft robotics, medical prosthetics, and human-machine interface.
1. Wu, W. Z., Qiu, G., Wang, Y. X., Wang, R. X., Ye, P. D., “Tellurene: its physical properties, scalable nanomanufacturing, and device applications”, Chem. Soc. Rev., 2018, 47, 7203-7212.
2. Wang, Y. X., Qiu, G., Wang, R. X., Huang, S. Y., Wang, Q. X., Liu, Y. Y., Du, Y. C., Goddard, W. A., Kim, M. J., Xu, X. F., Ye, P. D., Wu, W. Z., “Field-effect transistors made from solution-grown two-dimensional tellurene”, Nature Electronics, 2018, 1, 228-236.
10:45 AM - *ES21.05.02
Printing Two-Dimensional Piezoelectric Layers Using Liquid Metal Reaction Media
Kourosh Kalantar-zadeh2,Nitu Syed1,Torben Daeneke1,Ali Zavabeti1
RMIT University1,University of New South Wales2Show Abstract
The recent exploration of two dimensional (2D) planes as piezoelectric structures has accelerated. Mechanical displacements, such as vibration, bending and stretching, are ubiquitously present in the ambient environment and 2D structures may facilitate their sensing and the harvesting of their kinetic energy to power miniaturised devices based on such piezoelectric materials. Peculiar qualities by 2D materials, including their lateral strength and high crystallinity along the planes, large surface area to mass ratios and compatibility with surface fabrication processes, provide the concept of 2D piezoelectric with great prospect for future industries.
Field of 2D piezoelectric materials can benefit from the emergence of crystals featuring high piezoelectric coefficients such as gallium phosphate (GaPO4). This 2D material is an archetypal piezoelectric with wide-ranging industrial applications. However, it does not naturally crystallise in a stratified structure and hence cannot be exfoliated using any of the conventional methods. Here we present a low temperature liquid metal 2D printing and synthesis strategy. Interfacial oxide layer of liquid gallium is exfoliated and surface-printed, followed by the vapour phase reaction between the gallium oxide sheet and phosphoric acid. The method gives access to large-area, uniform 2D GaPO4 nanosheets of unit cell thickness (~1.1 nm), while featuring wafer scale lateral dimensions. The unit cell thick nanosheet presents a large effective out-of-plane piezoelectric coefficient of nearly 8 pm/V. The developed liquid metal based process is also suitable for the synthesis of free-standing 2D GaPO4 nanosheets over micron sized cavities. The presented low temperature process is compatible with a variety of electronic device fabrication procedures, providing a facile route for the development of 2D piezoelectric devices for sensing and energy harvesting.
1- Zavabeti, A. et al. A liquid metal reaction environment for the room-temperature synthesis of atomically thin metal oxides. Science 358, 332, (2017).
2- Carey, B. J. et al. Wafer-scale two-dimensional semiconductors from printed oxide skin of liquid metals. Nat. Commun. 8, 14482, (2017).
3- Daeneke, T. et al. Liquid metals: fundamentals and applications in chemistry. Chem. Soc. Rev., 47, 4073, (2018).
4- Syet, N. et al. Printing two-dimensional gallium phosphate out of liquid metal. Nat. Commun. 3618, (2018).
11:15 AM - *ES21.05.03
Piezoelectric Nanotransducers: Unique Advantages, Challenges and Possible Solutions
University of Tor Vergata1Show Abstract
The properties of systems and, in particular, of transducers are greatly affected by their dimensions due to both classic scaling laws and, at nanoscale, quantum effects. For this reason, nanoscale piezoelectric transducers can help to overcome the limits of conventional piezoelectrics.
In particular, nanoscale materials can withstand larger deformations (which translate into higher piezopotentials, more robust and flexible devices and extended dynamic ranges), have higher piezoelectric coefficients, offer superior mechanical force-to-displacement sensitivities and operate at higher speed. Moreover, several materials which are not piezoelectric in their bulk form due to the opposite orientations of adjacent atomic layers, are piezoelectric as single layer. Besides, the working mechanisms of some devices are only possible at nanoscale; for instance, it has been suggested  that floating ghost gates can be created by tunneling triboelectrification  for tuning piezotronic devices with the extraordinary spatial resolution of AFM tips. Additionally, at nanoscale there are many more degrees of freedom for designing piezoelectric transducers  and, in comparison with conventional piezoelectrics, there can be more choices for the types of mechanical input, the positions of the contacts, the dimensionalities, and the shapes [3,4]. Downscaling also uniquely offers the opportunity to fabricate piezoelectric transducers which can be used in vivo for a variety of tasks [5,6].
Piezoelectric nanotransducers may offer outstanding advantages in comparison with conventional piezoelectrics, but practical applications can be complicated by many difficulties, with special reference to synthesis, characterization, modeling and device implementation. We will discuss some of the most important open challenges and also some general strategies to address them, namely, with reference to piezoelectric quasi-1D nanostructures (e.g. ZnO nanowires), rational design of solution-growth synthesis procedures , real time growth monitoring , dynamic synthesis procedures  and 3D geometrical characterizations from conventional SEM images .
 R. Hinchet, U. Khan, C. Falconi, S.W. Kim, Piezoelectric properties in two-dimensional materials: Simulations and experiments, Mater. Today. 21 (2018) 611–630. doi:10.1016/j.mattod.2018.01.031.
 S. Kim, T.Y. Kim, K.H. Lee, T.H. Kim, F.A. Cimini, S.K. Kim, R. Hinchet, S.W. Kim, C. Falconi, Rewritable ghost floating gates by tunnelling triboelectrification for two-dimensional electronics, Nat. Commun. 8 (2017) 1–7. doi:10.1038/ncomms15891.
 C. Falconi, G. Mantini, A. D’Amico, Z.L. Wang, Studying piezoelectric nanowires and nanowalls for energy harvesting, Sensors Actuators, B Chem. 139 (2009) 511–519. doi:10.1016/j.snb.2009.02.071.
 R. Araneo, G. Lovat, P. Burghignoli, C. Falconi, Piezo-semiconductive quasi-1D nanodevices with or without anti-symmetry, Adv. Mater. 24 (2012) 4719–4724. doi:10.1002/adma.201104588.
 C. Falconi, A. D’Amico, Z.L. Wang, Wireless nanosensors and nanoactuators for in-vivo biomedical applications, in: Eurosensors, Göteborg, 2006.
 C. Falconi, A. D’Amico, Z.L. Wang, Wireless Joule nanoheaters, Sensors Actuators, B Chem. 127 (2007) 54–62. doi:10.1016/j.snb.2007.07.002.
 G. Arrabito, V. Errico, Z. Zhang, W. Han, C. Falconi, Nanotransducers on printed circuit boards by rational design of high-density, long, thin and untapered ZnO nanowires, Nano Energy. 46 (2018) 54–62. doi:10.1016/j.nanoen.2018.01.029.
 A. Orsini, C. Falconi, Real-time monitoring of the solution growth of ZnO nanorods arrays by quartz microbalances and in-situ temperature sensors, Sci. Rep. 4 (2014) 1–7. doi:10.1038/srep06285.
 A. Mencattini, A. Orsini, C. Falconi, 3D Reconstruction of Quasi-1D Single-Crystal Nanostructures, Adv. Mater. 27 (2015) 6271–6276. doi:10.1002/adma.201503522.
11:45 AM - ES21.05.04
Wearable Multiphasic PVDF-Based Energy Harvesting Fabrics—Enhancement of the Piezoelectric and Dielectric Properties of Electrospun PVDF Fibers Through Incorporation of Barium Titanate Nanoparticles and Graphene
Walker Tuff1,Joshua Lor1,Saquib Ahmed2,Sankha Banerjee1
California State University, Fresno1,Buffalo State College2Show Abstract
Piezoelectric composites have been extensively studied for their energy harvesting applications, but there has been limited research into noninvasive wearable piezoelectric energy harvesters of human motion. Therefore, lead-free wearable polyvinylidene fluoride (PVDF)-based energy harvesting fabrics are investigated in this work. An electrospinning method was used to fabricate PVDF, PVDF-barium titanate (PVDF-BT), PVDF-graphene, and PVDF-BT-graphene fibers. The volume fractions of BT and graphene were varied from 0.01 to 0.10, and a loom was used to weave the fibers into a fabric for testing. The properties of the textiles were measured before and after exposure to a contactless corona-discharge plasma to determine if additional pooling enhanced the performance of the fabrics. The piezoelectric strain coefficient, d33, of the fabrics was measured using a piezometer at a frequency of 110 Hz. The impedance, resistance, conductance, and capacitance were measured using an impedance analyzer over frequency ranges of 20 Hz to 200 Hz and 20 Hz to 10 MHz. The geometric parameters of the textiles were also measured to calculate the resistivity, conductivity, and dielectric constant. The surface morphology of the textiles was analyzed with the aid of a scanning electron microscope.
ES21.06: Nanogenerators and Piezotronics I
Wednesday PM, April 24, 2019
PCC North, 100 Level, Room 132 C
1:30 PM - ES21.06.01
Piezo-Phototronic Effect Enhanced Photoelectrocatalysis
Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences1Show Abstract
TiO2 is a well-known photocatalyst used for water splitting, pollutant removal, antibacterial application, etc. How to increase the efficiency by overcoming their limitation including fast recombination of photoexcited carriers, limited light utilization are still great challenge.
In this talk, I will introduce our recent research progresses in piezo-phototronic effect enhanced photodynamic bacteria killing wound healing, and photoelectrocatalysis. For increase of the photodynamic induced bacteria killing based on TiO2, an internal piezoelectric field was built by inserting a ferroelectric semiconductor barium titanate (BaTiO3) nanolayer between TiO2 and plasmonic gold nanoparticles (Au NPs). Plasmonic Au NPs broadened the light absorbance to visible region and generated hot electrons. BaTiO3 with piezo-phototronic effect created a favorable band bending for facilitating electron transportation, thus enhancing the separation of electron-hole pairs and photoinduced bacteria killing. With the enhancement of photoelectrochemical performance, it was used as a skin antibacterial coating for photodynamic bacterial killing and promotion of skin wound healing in vitro and in vivo. We also used the piezoelectric effect enhanced full-spectrum Photoelectrochemical photoelectrocatalysis with multilayered coaxial titanium dioxide/barium titanate/silver oxide (TiO2/BTO/Ag2O) nanorod array as the photoanode. The vertically grown nanorods ensured the good electron conductivity, which enabled the fast transport of the photogenerated electrons for photoelectrocatalysis. The polar charge-created field induced by the polarized BaTiO3 nanolayer can effectively promote the separation and suppress the recombination of the photocarriers generated by TiO2 and Ag2O. The solarcatalytic performance of the heterostructure was evaluated via the PEC performance under full solar spectrum from UV, visible, to NIR light. The ternay hetero-nanorod array exhibited highly improved PEC activity and high stability. These works open new avenue for developing heterojunction for improving photocatalysis with piezoelectric effect.
1. Xin Yu, Zhenhuan Zhao, Jian Zhang, Weibo Guo,Jichuan Qiu, Deshuai Li, Xiaoning Mou, Linlin Li*, Aixue Li*, Hong Liu*. Small. 2016, 12, 2759.
2. Xin Yu, Zhenhuan Zhao, Jian Zhang, Weibo Guo, Linlin Li*, Hong Liu*, Zhong Lin Wang*. CrystEngComm 2017, 19, 129.
3. Jichuan Qiu, Kun Zhao, Linlin Li, Xin Yu, Weibo Guo, Shu Wang, Xiaodi Zhang, Caofeng Pan*, Zhong Lin Wang*, HongLiu*. Nano Res. 2017, 10, 776.
4. Xin Yu, Shu Wang, Xiaodi Zhang, Anhui Qi, Xiran Qiao, Zhirong Liu, Mengqi Wu, Linlin Li*, Zhong Lin Wang*. Nano Energy, 2018, 46, 29
1:45 PM - ES21.06.02
Structure Design and Enhancing the Performance by Dielectric Modulation of TENG for Harvesting the Blue Energy
Chongqing University1Show Abstract
Triboeletric nanogenerator（TENG）has been considered to be a more effective technology to harvest various types of mechanic vibration energies such as wind energy, water energy in the blue energy and so on. Considering the vast energy from the blue oceans, harvesting of the water energy has attracted huge attention. There are two major types of “mechanical” water energy, water wave energy in random direction and water flow kinetic energy. Here, we successfully developed multifunctional TENGs that can be used to harvest the blue energy. Moreover, surface charge density of tribo-layer is the most key-point parameter for developing high performance TENG. Most of the previous works were focus on the surface structural/chemical modification, nevertheless the internal space of the tribo-layer and its mechanism exploration were less investigated. Herein, internal space charge zones are built through imbedding ravines and gullies criss-cross gold layers in near-surface of tribo-layer, which leads to the high output performance of TENG. At the same time, the tribo-laryer of TENGs have been fabricated via dispersing the lead-free piezoelectric materials to increase the output performances, the fundamental mechanism of the TENG has been discussed from the perspectives of dielectric modulation.
2:00 PM - ES21.06.03
Unidirectionally Polarized Diphenylalanine Nanotube Based Piezoelectric Energy Generator
Ju Hyuck Lee1,2
Daegu Gyeongbuk Institute of Science and Technology1,University of California, Berkeley2Show Abstract
Piezoelectricity is defined as the interconversion between mechanical and electrical energy induced by charge redistribution and separation when mechanical or electrical stimuli are applied to materials that do not have inversion symmetry. Although various conventional inorganic piezoelectric materials exhibit strong piezoelectric property, these materials often require substances that are harmful to the environment / human body or harmful to the environment during the fabrication process. Many natural biomaterials (eg, amino acid, peptide, protein, and virus) that can be synthesized in an environmentally friendly manner have been found to have piezoelectric properties and it is comparable to conventional piezoelectric materials. Recently, self-assembled diphenylalanine (FF) nanotubes have been reported to have strong piezoelectric properties comparable to conventional piezoelectric materials. However, the difficulty of fabricating unidirectionally polarized FF nanotubes that can convert mechanical forces into electrical energy has been a major impediment to the realization of high power bio-piezoelectric devices. Here, we develop a novel fabrication process to synthesize large-scale aligned and uni-polarized FF nanotubes. We use a meniscus-driven self-assembly process which is environmental friend process. By controlling the thermodynamic and kinetic parameters of fabrication process, we synthesized FF nanostructures ranging from vesicles to aligned peptide nanotubes. The resulting horizontally aligned FF nanotubes have unidirectional polarization. Furthermore, this synthesis process allows us to easily scale-up to form large-area coatings that we use to develop piezoelectric energy generator.
2:15 PM - ES21.06.04
Enhanced Triboelectric Effect in PVDF—Changing Its Surface Roughness, Polarizability and Hydrophobicity
Huidrom Hemojit Singh1,Neeraj Khare1
Indian Institute of Technology Delhi1Show Abstract
With the advancement in technology and the urgent need for clean energy sources, triboelectric nanogenerator also known in short as TENG starts gaining lots of attention in recent years. TENG works on the principle of contact electrification, in which when two different materials come into contact charges are generated on the surface of the materials.[1–3] The amount of charges generated depend on various parameters, like surface roughness, work function, polarizability and hydrophobicity of the materials. [4–6]
In the present work, we have modified surface roughness, hydrophobicity and polarizability of polyvinylidene fluoride (PVDF) by incorporating hydrothermally synthesized ZnO nanorods into PVDF. The changes in the above properties of PVDF lead to the enhanced triboelectric effect of PVDF. The films were prepared using a simple drop casting method, and no surface treatment or complex film synthesis techniques were not employed. TENGs fabricated by coupling ZnO-PVDF film with polytetrafluoroethylene (PTFE) showed a much enhanced triboelectric output of voltage of ~119 V and short circuit current of ~1.6 µA. The instantaneous output power is 65.6% more as compared to PVDF/PTFE based TENG. The enhancement in the performance of the TENG has been correlated with the changes in the properties of PVDF. We believe that this work will provide a simple yet effective way of enhancing the triboelectric effect of materials mainly ferroelectric polymers.
1. L. Lin, S. Wang, S. Niu, C. Liu, Y. Xie, and Z. L. Wang, ACS Appl. Mater. Interfaces 6, 3031 (2014).
2. Q. Zhang, Q. Liang, Q. Liao, F. Yi, X. Zheng, M. Ma, F. Gao, and Y. Zhang, Adv. Mater. 29, (2017).
3. J. Qian, X. Wu, D.-S. Kima, and D.-W. Lee, Sensors Actuators A Phys. 263, 600 (2017).
4. P. Bai, G. Zhu, Z. H. Lin, Q. Jing, J. Chen, G. Zhang, J. Ma, and Z. L. Wang, ACS Nano 7, 3713 (2013).
5. S. G. Lee, J.-W. Ha, E.-H. Sohn, I. J. Park, and S.-B. Lee, Appl. Surf. Sci. 390, 339 (2016).
6. H. H. Singh and N. Khare, Nano Energy 51, 216 (2018).
3:30 PM - ES21.06.05
Additive Patterning of Multilayer Ferroelectric Oxide Devices by Inkjet Printing
Aleksander Matavz1,2,Andreja Bencan1,2,Susan Trolier-McKinstry3,Barbara Malic1,2,Vid Bobnar1,2
Jozef Stefan Institute1,Jozef Stefan International Postgraduate School2,The Pennsylvania State University3Show Abstract
The concepts such as Internet of Things—with an aim to equip the regular, everyday objects with intelligence and interconnect them into a network of smart devices—are thought to revolutionize the way of living. The widespread of these devices would require cost- and waste- efficient processing, which cannot be realized by a traditional photolithography-based processing. Inkjet printing—an additive patterning technique—is a powerful alternative to the traditional technology, and enables a direct deposition of micro-sized structures with digitally-defined geometry. Yet, due to strongly interdisciplinary nature of inkjet printing, it is still facing major problems when it comes to the realization of fully-printed devices.
To approach this challenge, we have systematically studied the inkjet printing process and developed a method for a reliable fabrication of all-oxide ferroelectric thin-film capacitors. The capacitors consist of lanthanum nickelate (LNO) electrodes and lead zirconium titanate (PZT) ferroelectric layer. To prepare the inks we first synthesized sol-gel precursor solutions and adjusted their physical properties by the addition of ethanolamine and ethylene glycol. The solvent composition was selected on the basis of our previous work to suppress the coffee stain formation of dried structures [A. Matavz et al., Appl. Phys. Lett. 113, 012904, 2018]. One of the most demanding issues in multilayer inkjet printing is the control over the wetting behavior throughout the fabrication process. To achieve this, we employed a few-nanometer-thick polymeric layer, which redefines the surface properties after each deposition step and ensures the repeatability during the fabrication of LNO/PZT/LNO stacks. The polymeric layer decomposes during annealing and does not influence the performance of capacitors.
The developed method proved to be extremely versatile: we printed LNO/PZT/LNO capacitors on silicon wafers, alumina substrates and nickel foils. The capacitors with 400 nm thick PZT layer show excellent electrical properties: the capacitance density of 30 nF/mm2 (corresponding to dielectric permittivity of 1350), typical ferroelectric hysteresis and piezoelectric coefficient of 80 pm/V. The printing method offers also the possibility of multilayer capacitor (MLC) processing. We successfully realized MLCs composed of three PZT layers on silicon wafers, which exhibit electromechanical properties superior to the single PZT layer capacitors. The results demonstrate the large potential of inkjet printing for the fabrication of high-quality ferroelectric devices and imply its role in a next-generation production of sensors, energy harvesters, and microelectromechanical systems.
3:45 PM - ES21.06.07
Conducting Polymer-Based Triboelectric Nanogenerators for Self-Powered, Transparent and Flexible System of Instantaneous Touch Visualization
Bo-Yeon Lee1,2,Keon Jae Lee1
Korea Advanced Institute of Science and Technology1,Seoul National University2Show Abstract
The development of the transparent and flexible power sources has attracted much interest for their potential in a broad range of applications from artificial skins to touch screen. Among them, a triboelectric nanogenerator (TENG), which is one of energy-harvesting devices, has been extensively investigated owing to several advantages such as cost-effectiveness, structural simplicity, wide material selection, and high conversion efficiency. Despite these attractive advantages, it remains a challenge to achieve a high output performance while preserving both the transparency and the flexibility because of the opaque and less flexible metal.
Here, we report a highly efficient, transparent and flexible TENG based on a transparent conducting polymer (TCP) and metallic nanowires. Metallic nanowire-embedded TCP layer, which played a role as a contact layer as well as an electrode, showed high tribonegativity as well as high transparency and flexibility. The output performance of the TENGs was optimized considering the triboelectric property of a counter contact layer and the physico-chemical properties of a TCP film. In our TCP-based TENG, the maximum power density was shown to be about 1.5 mW/cm2 for the external resistance of about 2 MΩ. This value is a quite large compared with the previous transparent and flexible TENGs. As a realistic application example of the TCP-based TENG, we demonstrated a user-interactive system for instantaneous touch visualization based on a transparent and flexible TENG and a voltage-driven display device. The electro-optic devices were operated by only one or a few gentle touch to our TCP-based TENGs. Our work will provide a viable framework to devise flexible and transparent power sources and sensors.
This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education(2018R1A6A3A01011608).
4:00 PM - ES21.06.08
Flexible and Controllable Piezo-Phototronic Pressure Mapping Sensor Matrix by ZnO NW/p-Polymer LED Array
Rongrong Bao1,Caofeng Pan1
Chinese Academy of Sciences1Show Abstract
Functional tactile sensing device is mandatory for next-generation robotics and human-machine interfaces since the emulation of touching requires large-scale pressure sensor arrays with high-spatial resolution, high-sensitivity, and fast-response. Some tactile sensors fabricated with organic transistors or micro-structured rubber layer pressure sensor arrays have been reported, whose working mechanism is based on changes in capacitance or resistance. Our group have demonstrated pressure sensor array base on piezotronic and piezo-phototronic effects. A spatial resolution of 120 μm was achieved for piezotronic pressure sensor array and an ultra-high resolution of 2.7 μm was derived from piezo-phototronic pressure sensor array using ZnO nanowire (NW)/p-GaN LEDs array. These devices provide stable, fast response, as well as parallel-reading detections of spatial pressure distributions. However, the lacking of flexibility with a rigid sapphire substrate prevents the NW-LEDs array device from applications as smart skin; and the pressure measuring range of the device is in a relatively high pressure region. Therefore, a flexible pressure mapping system with moderate spatial-resolution become necessary and may find numerous potential applications in human-machine interfaces.
Organic/inorganic hybridized LEDs are drawing tremendous attentions because of their high flexibility. Among them, n-ZnO and p-poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate (PEDOT:PSS) hybridized inorganic/organic LED has aroused great technological and scientific interests due to the excellent optoelectronic properties of ZnO and the high flexibility, low-cost, easy fabrication, potential for large area deposition and commercial availability of PEDOT:PSS. Here, we demonstrate a flexible LED array composed of PEDOT:PSS and patterned ZnO NWs for mapping spatial pressure distributions. By utilizing strain-induced negative piezoelectric polarization charges presented at local interface of the pn junction, piezo-phototronic effect has been applied to modify the band structure through reducing the barrier height for hole injections from PEDOT:PSS side, and thus facilitate the recombination between electrons and holes in ZnO side for enhancement of light emitting intensity. Therefore, the pressure distribution is obtained by parallel-reading the illumination intensities of LED pressure sensor array. The spatial resolution is achieved as high as 7 μm by fabricating ZnO nanowires on flexible substrate. By controlling the growth conditions of the ZnO nanowire array, a wide range of pressure measurements from 40 MPa to 100 MPa are derived under different ZnO morphologies. These devices may find prospective applications as electronic skins by taking advantage of their high spatial-resolution, flexibility and wide pressure mapping range.
 a) S. C. B. Mannsfeld, B. C. K. Tee, R. M. Stoltenberg, C. V. H. H. Chen, S. Barman, B. V. O. Muir, A. N. Sokolov, C. Reese, Z. Bao, Nature Materials 2010, 9, 859; b) J. J. Boland, Nature Materials 2010, 9, 790; c) K. Takei, T. Takahashi, J. C. Ho, H. Ko, A. G. Gillies, P. W. Leu, R. S. Fearing, A. Javey, Nature Materials 2010, 9, 821.
 a) B. C. K. Tee, A. Chortos, R. R. Dunn, G. Schwartz, E. Eason, Z. A. Bao, Advanced Functional Materials 2014, 24, 5427; b) Y. Wang, L. Wang, T. T. Yang, X. Li, X. B. Zang, M. Zhu, K. L. Wang, D. H. Wu, H. W. Zhu, Advanced Functional Materials 2014, 24, 4666; c) C. Y. Hou, H. Z. Wang, Q. H. Zhang, Y. G. Li, M. F. Zhu, Advanced Materials 2014, 26, 5018; d) S. Jung, J. H. Kim, J. Kim, S. Choi, J. Lee, I. Park, T. Hyeon, D. H. Kim, Advanced Materials 2014, 26, 4825; e) Q. Sun, D. H. Kim, S. S. Park, N. Y. Lee, Y. Zhang, J. H. Lee, K. Cho, J. H. Cho, Advanced Materials 2014, 26, 4735.
 a) W. Z. Wu, X. N. Wen, Z. L. Wang, Science 2013, 340, 952; b) C. F. Pan, L. Dong, G. Zhu, S. M. Niu, R. M. Yu, Q. Yang, Y. Liu, Z. L. Wang, Nat. Photonics 2013, 7, 752;
4:15 PM - ES21.06.09
Quantifying the Triboelectric Series
Haiyang Zou1,Ying Zhang1,Litong Guo1,Zhong Lin Wang1
Georgia Institute of Technology1Show Abstract
Triboelectrification is a well-known effect that occurs anywhere and anytime in nature and in our life. Although this effect has been known for over 2600 years and each and every material exhibits triboelectrification, as a key material’s genome, its quantification has not been standardized and quantified in material science. The only available tool is a triboelectric series that gives a qualitative ranking about the triboelectric polarization of some common materials. Here, for the first time, we introduce a universal standard method to quantify the triboelectric series for a wide range of polymers, establishing a fundamental materials property of quantitative triboelectrification. By measuring the tested materials with a liquid metal in an environment under well-defined and fixed conditions, the proposed method standardizes the experimental set up for uniformly quantifying the surface triboelectrification of general materials. The normalized triboelectric charge density (TECD) was defined and derived to reveal the intrinsic character of polymers for gaining or losing electrons. A table is given regarding the TECD of over 50 materials. This first quantitative triboelectric series will be a textbook standard for implementing the application of triboelectrification for energy harvesting and self-powered sensing.
ES21.07: Poster Session
Wednesday PM, April 24, 2019
PCC North, 300 Level, Exhibit Hall C-E
5:00 PM - ES21.07.01
Piezo-Phototronic Effect Enhanced Performance of the Flexible Microwire Photodetectors
Qianqian Du1,Shunming Zhu1,Jiandong Ye1,Kun Tang1,Youdou Zheng1,Shulin Gu1
Nanjing University1Show Abstract
Owing to the large surface to volume ratio and tunable surface morphologies, photodetectors based on low-dimensional nanostructures exhibit superior performance, thus many efforts have been made to optimize the photoelectric devices . Zinc oxygen(ZnO) with the advantages of being flexible and fast and having high resolution in stress/ pressure sensor applications, high chemical stability and outstanding optical properties in optoelectronics applications, has attracted significant attention in recent years. In this study, the ZnO microwires were fabricated. by a simple one-step chemical vapor deposition(CVD) method. We demonstrated photodetectors based ZnO microwires modified with NiO on a rigid SiO2/Si substrate and the other on flexible polyethylene terephthalate (PET), respectively. We also investigated the electronic property of the devices with stress and light in detail. The results indicated that The piezo-phototropic effect can effectively enhance the performance of ZnO photodetector.
This research was supported by the National Natural Science Foundation of China (Nos. 61504057, 61574075, 61674077) and the Natural Science Foundation of Jiangsu Province (Nos. BK20150585).
 Choi M, Murillo G, Hwang S, Kim J W, Jung J H, Chen C-Y and Lee M 2017 Nano Energy 33 462-8
 Thakur P, Kool A, Hoque N A, Bagchi B, Khatun F, Biswas P, Brahma D, Roy S, Banerjee S and Das S 2018 Nano Energy 44 456-67
5:00 PM - ES21.07.02
High-Performance Piezoelectric Nanogenerators Based on Composite Thin Films
Su Yeon Lee1,Eun Jung Lee1,Sunho Jeong1,Youngmin Choi1
Energy harvesting that can scavenge various kinds of mechanical energy from several different sources have attracted great attention. In particular, a flexible energy-harvesting device consisting of piezoelectric materials has been studied as a power source for flexible and wearable electronic devices because the piezoelectric materials can effectively convert to electrical energy from mechanical energy. Recently, many researchers have attempted to achieve highly efficient energy-harvesting devices using several fabrication methods. However, there are still the challenge problems with flexible piezoelectric nanogenerators. Here we report the flexible piezoelectric nanogenerators (PNGs) based on composite thin films comprising amine-functionalized lead zirconate titanate (PZT) nanoparticles (PZT-NH2 NPs) and a thermoplastic triblock copolymer. Without additional dispersants, the uniform distribution of PZT-NH2 NPs in the polymer composite improves the piezoelectric power generation compared to that of a PNG device using pristine PZT NPs. This unique composite behavior allows the PZT-NH2 NP-based flexible PNG to exhibit a high output voltage of 65 V and current of 1.6 μA without time-dependent degradation. This alternating energy from the PNG can be used to charge a capacitor and operate light-emitting diodes through a full bridge rectifier. Furthermore, the proposed PNG is demonstrated as a promising energy harvester for potential applications in self-powered systems.
5:00 PM - ES21.07.03
Enhanced Piezoelectric Nanogenerator Performance by Point Defect Control of MoS2
Sang A Han1,2,Ka-Young Park3,Jung Ho Kim1
University of Wollongong1,Sungkyunkwan University2,Sejong University3Show Abstract
The piezoelectric characteristics of two-dimensional materials are of great interest for high-performance piezoelectric potential applications. The CVD-based large-area monolayer MoS2 is essential for practical applications. However, the CVD-based MoS2 has the intrinsic defect of sulfur vacancies during the growth process, and these defects play an important role in screening the piezoelectric potential. So only small piezoelectric potential induced power output has been observed from the CVD-grown MoS2. Here we demonstrate a high performance piezoelectric nanogenerator using CVD-based monolayer MoS2 nanosheet by an additional sulfur treatment process during the MoS2 growth process. The measured piezoelectric coefficient (d11) of the CVD-grown large-area monolayer MoS2 nanosheet is 3.73 pm V-1 using lateral PFM methods, and it generates a peak power density of 0.73 pW, which is 10 times higher than that of the pristine monolalyer MoS2 nanosheet.
5:00 PM - ES21.07.04
Nylon 11-MoS2 Composite Layer with High Performance for Triboelectric Nanogenerator
Minje Kim1,Sol Lee1,Anh Cao Viet1,Daehoon Park1,Junghyo Nah1
Chungnam National University1Show Abstract
Triboelectric nanogenerators(TENGs) have gained much attention thanks to their relatively high output power generation by scavenging vibrating resources that exist in our living environment. To date, a number of approaches, such as surface patterning, dielectric permittivity modulation, chemical functionalization, have been introduced to enhance output performance of the TENGs. However, the TENG’s output performance has still been limited due to relatively low output current density on the triboelectric frictional surfaces. Therefore, simple and effective methods are necessary to boost the output current density of the TENG, which further extend the performance limit of the TENGs.
In this report, we adopted the composite structure consisting of MoS2 flakes and ferroelectric Nylon 11 polymer to improve output current density. Here, ferroelectric Nylon 11 provides a knob to adjust surface triboelectric charge density by surface polarization. In addition, MoS2 provides the trap states to further increase charge density in the composite structure. Using these two knobs, the output charge density was greatly improved in comparison to the TENG without the MoS2 particles. Specifically, 5-fold higher current density was obtained by using the polarized MoS2-Nylon 11 composite layer compared with the device fabricated only with non-polarized Nylon 11. Consequently, the maximum output power density of ~40 mW/cm2 was achieved in our work. The approach introduced here provides simple strategy to effectively extend the output performance limit of TENGs.
Acknowledgement: This subject is supported by Korea Ministry of Environment(MOE) as Advanced Technology Program for Environmental Industry Program.
5:00 PM - ES21.07.05
Role of Indium Zinc Oxide-Based Interfacial Layer for High Performance Triboelectric Nanogenerators
Daehoon Park1,Kyung Seok Han1,Sol Lee1,Junghyo Nah1
Chungnam National University1Show Abstract
Triboelectric nanogenerators (TENGs), which can effectively convert various mechanical stimuli to electricity by using a relatively simple device structure and cost-efficient, areconsidered as a promising candidate for coping with gradually increasing energy demands. To date, various research efforts have been reported to enhance the output performance of TENGs, which have greatly improved their output performance. However, triboelectric output performance enhancement is still hindered by its relatively low output current compared to its output voltage. Thus, further study is necessary to boost the output current density to further extend the performance limit of the TENG.
In this work, we report the output performance enhancement method by inserting an indium zinc oxide (IZO) layer under polydimethylsiloxane (PDMS). Specifically, the 0.5 M IZO solution was prepared by spin-coating on stainless steel sheet, followed by curing and annealing processes. Next, IZO layer is buried by spin-coated PDMS. The TENG with a buried layer is relatively uninfluenced by surface wear-out. Furthermore, its output enhancement is considerably enhanced. The role of IZO layer is two folds: electron discharge from interface states at the IZO-PDMS interface and electron supply from the IZO layer by energy band bending during contact-separation motion. Consequently, the output performance of the TENG with an IZO layer is remarkably improved by adopting the IZO layer, generating an output power density of ~25 mW/cm2. Especially, about 9-fold increase of output current was observed in TENG with an IZO layer due to additional electron supplying effect by n-type semiconductor IZO. The approach presented here is a simple method for boosting of the performance of TENGs and effectively alleviating their susceptibility to friction surface wear-out.
This research is supported by Korea Ministry of Environment(MOE) as Advanced Technology Program for Environmental Industry Program
5:00 PM - ES21.07.06
A Novel Multi-Functional Self-Powered Pressure Sensor with Hierarchical Wrinkle Structure
Liming Miao1,Hang Guo1,Ji Wan1,Haobing Wang1,Xiaoliang Cheng1,Haixia Zhang1
Peking University1Show Abstract
Novelty: This paper reports a novel multi-function self-powered pressure sensor with hierarchical wrinkle structure which is thin and flexible. Due to the sensitive hierarchical wrinkle structure, the sensor shows the sensitivity of 2.0 kPa-1 and the excellent response performance of 0.15 ms (risetime) and 0.7 ms (releasetime). In addition, the surface charges deriving from the contact of PDMS and ITO on the wrinkle structure enable the sensor to be a generator and differentiate various mechanical stimuli.
Background: With the development of electronic skins and wearable devices, flexible sensors based on capacitive effect due to its stability, are now concerned about by more and more people. But most of them require multi-step process and complicated fabrication because of complexly designed dielectric layer. PDMS wrinkle structure fabricated by C4F8 plasma treating has been applied to triboelectric nanogenerator (TENG) and have the advantage of simple fabrication. However, the sensor with monolayer wrinkle structure shows low sensitivity. Here, we introduce hierarchical PDMS wrinkle structure into the capacitive effect pressure sensor to improve the performance of the sensor and meanwhile integrate the feature of energy harvesting.
Fabrication Process: The vacuum degassed mixture of PDMS base and cross-linker is spin coated on the indium tin oxide (ITO) coated polyethylene terephthalate (PET) film. Then heat the thin PDMS/ITO/PET film at 100 degree celsius for 45 seconds. Next implement a C4F8 plasma treatment for 1000 seconds, after which heat the film till the curing of the thin PDMS layer. Finally, cover the wrinkle-structrued film with another ITO/PET film. The thickness and area of the sensor are about 260 μm and 6.25 cm2, respectively.
Working principle: As a capacitive effect sensor, the ITO layers work as two conductive electrodes and the dual-scale wrinkle structure, the thin PDMS layer and the air work as dielectric layer. While as a generator, the PDMS and ITO work as charges generation surface and the air between the wrinkle gap enables PDMS layer and ITO layer to contact and separate. The hierarchical wrinkle structure manages differentiating normal pressure and bending.
Experimental Results: Since extending C4F8 plasma treating time to 1000s can produce hierarchical wrinkle structure on the PDMS surface, the sensitivity in the relatively low pressure regime (0-500 Pa) can get an obvious promotion from 0.5 kPa-1 (50s plasma treating), 1.0 kPa-1 (500s plasma treating) to 2.0 kPa-1 (1000s plasma treating). Moreover, in the relatively high pressure regime (more than 1500 Pa), the sensitivity of the sensor gets a slight promotion from 0.1 kPa-1 (50s & 500s plasma treating time) to 0.2 kPa-1 (1000s plasma treating time). Moreover, the response performance is excellent with the release-time is 0.7 ms and the rise-time is even only 0.15 ms. When pressure is applied, the small wrinkle firstly works and then sense the pressure quickly and sensitively by forming deformation, thus the sensitivity of the pressure sensor in the relatively low pressure regime can be highly enhanced and the response time is extremely short. When the pressure is applied extremely high, the big wrinkle begins to work and shows a sensitivity of 0.2kPa-1 once bigger than that of a PDMS plat.
As a TENG, the output voltage of the sensor under bending stimuli is about 300 V, while that of the sensor under pressure stimuli is only about 75 V. The output current of the former is about 3μA, while the latter is about 17 μA. The wave pattern under pressure stimuli is more sharp than that under bending stimuli. The reason for the feature of mechanical stimuli differentiation of the device can be attributed to the hierarchical wrinkle structure. The two forces can make hierarchical wrinkles contact with the PET/ITO with different deformation which leads to different contact area thus results in output voltage and current.
5:00 PM - ES21.07.07
Joshua Seylar1,Ruel McKenzie1
University of Akron1Show Abstract
Helicenes are a unique group of helically conformed aromatic compounds which have been shown to possess potentially useful properties. Pertinent to this proposed research, helicenes have been shown both computationally and experimentally to be piezoelectric. It is the intent of this research to utilize functionalized helicenes as monomers in the backbone of existing polymer systems. In this way, a new multi-functional class of polymers will be developed which possess the inherent properties of helicenes. These molecules derive their piezoelectric properties from the inherent strain in the molecule originating from their helical shape. This is unlike existing piezoelectric polymers such as poly- (vinylidene fluoride) (PVDF) whose piezoelectric properties originate from interaction between dipoles in the polymer structure. This research will begin with the synthesis of a diol-functionalized, nine-ringed helicene for application in a proof-of-concept polyester system. Initial characterization of this polymer will provide insight the as-synthesized properties of this novel polymer, and later optimization of piezoelectric properties will show the presence and extent of the functional activity of the polymer. The capability of these molecules to be adapted for use in various polymer chemistries give this new class of polymers potential for use in applications where material properties have previously limited the versatility of piezoelectric polymers.
5:00 PM - ES21.07.08
Localized Plasmon-Stimulated Triboelectric Nanogenerator
Gi Hyeon Han1
We report for increase the surface charge density of the TENG using a surface plasma resonance. Resonant energy transfer (RET) generates electron–hole pairs in the semiconductor by the dipole–dipole interaction between the plasmonic metal and semiconductor. A wide range of enhancement phenomena have been observed from enhanced light trapping in semiconductor loaded with plasmonic nanoparticles to plasmonically assisted hot carrier generation for TENG.
5:00 PM - ES21.07.09
Tunable Tribotronic Dual-Gate Logic Devices Based on 2D MoS2 and Black Phosphorus
Beijing Institute of Nanoenergy and Nanosystems1,University of Chinese Academy of Science2Show Abstract
With the Moore’s law hitting the bottleneck of scaling-down in size (below 10nm), personalized and multifunctional electronics with an integration of two-dimensional (2D) materials and self-powering technology emerges as a new direction of scientific research. Triboelectric nanogenerators (TENGs) that efficiently convert mechanical energy into electric power have great potential in self-powered smart systems and modulating semiconductor devices. As the basic components in integrated circuit, logic circuits based on 2D materials transistors have a promising potential. Here, we report a tunable tribotronic dual-gate logic device based on MoS2 FET, black phosphorus FET and a sliding mode TENG. Triboelectric potential produced from the sliding mode TENG under an external displacement can efficiently drive the complementary transistors and logic devices without applying a gate voltage. The high-κ top gate dielectrics contributes to the increase of the effective capacitance of the device, leading to high performance tribotronic transistors with on/off ratio exceeding 106 and cutoff current below 1 pA/μm, which are the best ever obtained. Tunable electrical behaviors of the logic device are also achieved according to different displacements of TENG coupled to the bottom gate, including tunable gains (improved to be ~13.8) and power consumptions (~1 nW). This work offers a low-power-consuming, active and a general approach to modulate semiconductor devices and logic circuits based on 2D materials with TENG, which can be used in micro-electromechanical systems, human–machine interfacing, data processing and transmission.
5:00 PM - ES21.07.10
An Amphibious Triboelectri