Nick Melosh, Stanford Univ
Woo Soo Kim, Simon Fraser Univ
Rebecca Kramer, Purdue University
George Malliaras, ENSM Saint-Etienne
MilliporeSigma (Sigma-Aldrich Materials Science)
BM4.1: Wearable Sensors and Devices I
Monday AM, November 28, 2016
Hynes, Level 2, Room 207
9:45 AM - *BM4.1.01
Wearable Sweat Sensors
Ali Javey 1
1 University of California, Berkeley Berkeley United StatesShow Abstract
Wearable sensor technologies play a significant role in realizing personalized medicine through continuously monitoring an individual’s health state. To this end, human sweat is an excellent candidate for non-invasive monitoring as it contains physiologically rich information. In this talk, I will present our recent advancement on fully-integrated perspiration analysis system that can simultaneously measure sweat metabolites, electrolytes and heavy metals, as well as the skin temperature to calibrate the sensors' response. Our work bridges the technological gap in wearable biosensors by merging plastic-based sensors that interface with the skin, and silicon integrated circuits consolidated on a flexible circuit board for complex signal processing. This wearable system is used to measure the detailed sweat profile of human subjects engaged in prolonged physical activities, and infer real-time assessment of physiological state of the subjects.
10:15 AM - BM4.1.02
Highly Stretchable Graphene-Based Electrochemical Sweat Sensors
Yunzhi Hua 1 , Matthew Yuen 1 , Yi-Kuen Lee 1
1 Hong Kong University of Science and Technology Hong Kong Hong KongShow Abstract
Wearable electrochemical sensors have attracted tremendous attention and are experiencing rapid growth in recent years. Non-invasive wearable sensors solve the potential issue in invasive sensors which may cause infection and painful feeling in the sensing area. Stretchable property also provides a comfortable wearable healthcare monitoring to users which is essential for the next generation of wearable sensors. Sweat, one of the most suitable biological fluids for non-invasive monitoring, contains multiple chemical elements relevant to abundant message about people’s health condition. Since the plasma ammonia is the main source of ammonia in human perspiration, the level of ammonium salt concentration in sweat is directly related to ammonia in plasma which is an excellent indicator of body health, for example, liver problem. In this work, a new type of non-invasive and stretchable potentiometric sweat sensor is developed by using all-solid-state ion-selective electrodes (ISEs) coupled with poly(dimethylsiloxane) (PDMS). The novel fabrication employs screen printing for both working and reference electrodes, incorporating graphene as ion-to-electron transducer with ammonium-selective membrane as the top layer. The advantages of PDMS-based substrate include simple fabrication with high flexibility of design and components. Stretchable PDMS-based substrate provides comfortability and ensures intimate contact with skin. Our stretchable electrochemical ammonium sensor also has the capability of maintaining its function under the intricate stress of bending and stretching on body while users perform daily activities. The tensile test results of our sensors showed stable potentiometric performance with negligible effect by mechanical deformation. Due to the unique nanostructure of graphene, the resulting potentiometric sensor displays a wide range of EMF response from 10-6 M to 1 M with high stability and sensitivity. Furthermore, the hydrophobic graphene layer contributes an excellent chemical sensing reversibility by preventing aqueous layer formation between the ISEs and conductive electrode surface. Such new stretchable electrochemical PDMS-based sweat sensor architecture will provide a revolutionary shift from hospital-centric healthcare monitoring to daily wearable-based personal healthcare management.
10:30 AM - BM4.1.03
Highly Stretchable, Transparent Ionic Touch Panel
Hyun-Hee Lee 1 , Chong-Chan Kim 1 , Jeong-Yun Sun 1 , KyuHwan Oh 1
1 Material Science and Engineering Seoul National University Seoul Korea (the Republic of)Show Abstract
The touch panel was developed decades ago and has become a popular input device in daily life. Because human-computer interaction is becoming more important, the next generation of touch panels require stretchability and bio-compatibility to allow integration with the human body. However, because most touch panels were developed based on stiff, brittle electrodes, electronic touch panels face difficulties to achieve such requirements. In this paper, for the first time, we demonstrate an ionic touch panel based on polyacrylamide hydrogel containing LiCl ions. The panel is soft and stretchable and thus, can sustain a large deformation. The panel can freely transmit light information through it because the hydrogel is transparent, with 99 % transmittance for visible light. A 1-dimensional touch strip was investigated to reveal the basic mechanism of sensing, and a 2-dimensional touch panel was developed to demonstrate its functionalities. The ionic touch panel was operated under high deformation with more than 1000% areal strain without sacrificing its functionalities. Furthermore, an epidermal touch panel on the skin was developed to demonstrate the mechanical and optical invisibility of the ionic touch panel through writing a word, playing piano, and playing a game.
10:45 AM - BM4.1.04
Enhancing the Interface between ZnO and Biomarkers through Room Temperature Ionic Liquids for Wearable Sweat Based Biosensing
Rujuta Munje 1 , Sriram Muthukumar 1 , Shalini Prasad 1
1 University of Texas at Dallas Richardson United StatesShow Abstract
Wearable biosensors using sweat based detection is a propeller for technological leap towards lancet-free health monitoring. Non-faradaic electrochemical sensors, which are label-free, cost-effective and are low-power applications, are desirable in the development of wearable biosensors. Nanomaterials such as Zinc oxide (ZnO) can be used to build non-faradaic electrochemical biosensors for enhanced sensitivity and specificity. The surface states of ZnO can be leveraged for immobilizing various linker molecules for ultra-specific detection of biomolecules. Also, the electrochemical modulation of ZnO due to linker binding can be optimized to achieve amplified sensor response. However, sweat based detection has unresolved challenges such as, stability of sensor element in human sweat pH range of pH 4.5 to pH 7 and multiple biomarker detection. In order to address the challenges related to stability, we studied the interactions of Room Temperature Ionic Liquid (RTIL) and ZnO thin film and its effective utilization for leveraging the stability of bio-immunoassay for sweat based detection. RTILs are being studied widely due to their desirable properties such as low volatility, wide electrochemical window and high thermal and chemical stability. We have used RTIL 1-Butyl-3-methylimidazolium tetrafluoroborate, which has been previously utilized for the detection of breast cancer gene and prostate specific antigen. We have used thiol based molecule Dithiobis succinimidyl propionate (DSP) for binding to zinc terminations of pulsed laser deposited ZnO thin film. In order to understand the RTIL interface between ZnO surface, linker and antibody , surface analysis was applied after performing Fourier Transform Infrared measurements on the layered structure of RTIL, DSP and Interleukin-6 (IL-6) antibody arranged in three different combinations on ZO surface. The optimized combination was recognized after identifying and correlating the absorption energy of different binding interactions on ZnO surface to the respective wavelengths. This analysis was also done for time-based stability study, where the same functionalized substrates were measured using FTIR for five weeks. We also performed electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measurements on the optimized stack to capture the electrochemical interactions. The capacitive component due to electrical double layer of RTIL and attached bio-immunoassay and resistive component due to charge transfer between DSP linker molecule and ZnO thin film was observed using Zview (Scribner Associates, Inc) software after fitting the data to equivalent circuit diagram. Hysteresis for time based variation in the sensor performance was compared by CV. Further, the optimized stack was used to detect the cytokine Interleukin-6 (IL-6) in sweat in range of 2 pg/mL to 20 pg/mL. It is capable of sensitively detecting 2 pg/mL IL-6 in synthetic sweat and shows stable performance over 5 week period.
BM4.2: Flexible and Stretchable Electronic Materials I
Woo Soo Kim
Monday AM, November 28, 2016
Hynes, Level 2, Room 207
11:30 AM - *BM4.2.01
Self-Powered Flexible Inorganic Electronic Systems
Keon Jae Lee 1
1 Department of Materials Science and Engineering King Abdullah University of Science and Technology Daejeon Korea (the Republic of)Show Abstract
This seminar introduces three recent progresses that can extend the application of self-powered flexible inorganic electronics. The first part will introduce self-powered flexible piezoelectric energy harvesting technology. Energy harvesting technologies converting external sources (such as vibration and bio-mechanical energy) into electrical energy is recently a highly demanding issue. The high performance flexible thin film nanogenerator was fabricated by transferring the perovskite thin film from bulk substrates for self-powered biomedical devices such as pacemaker and brain stimulation. The second part will introduce flexible electronics including large scale integration (LSI) and high density memory. Flexible memory is an essential part of electronics for data processing, storage, and radio frequency (RF) communication. To fabricate flexible large scale integration and fully functional memory, we integrated flexible single crystal silicon transistors with 0.18 CMOS process and memristor devices. The third part will discuss the flexible GaN/GaAs LED for implantable biomedical applications. Inorganic III-V light emitting diodes (LEDs) have superior characteristics, such as long-term stability, high efficiency, and strong brightness. Our flexible GaN/GaAs thin film LED enable the dramatic extension of not only consumer electronic applications but also the biomedical devices such as biosensor or optogenetics. Finally, we will discuss laser material interaction for flexible and nanomaterial applications. Laser technology is extremely important for future flexible electronics since it can adopt high temperature process on plastics, which is essential for high performance electronics, due to ultra-short pulse duration. (e.g. LTPS process over 1000 °C) We will explore our new exciting results of this field from both material and device perspective.
Related References (from Keon’s group as corresponding authors)
 Nano Letters 11, 5438, 2011.  Nano Letters 10, 4939, 2010.  Nano Letters 12, 4810, 2012.  Nano Letters 14, 7031, 2014.  Adv. Mater, 26, 2514, 2014.  Adv. Mater. 26, 4880, 2014.  Adv. Mater, 26, 7480, 2014.  Adv. Mater. 24, 2999, 2012.  Adv. Mater. 27, 3982, 2015.  Adv. Mater. 27, 2866, 2015.  Adv. Mater. 10.1002/adma201602339.  Energy Environ. Sci. 8, 2677, 2015.  Energy Environ. Sci., 7, 4035, 2014.  ACS Nano 7, 11016, 2013.  ACS Nano 9, 4120, 2015.  ACS Nano, 10, 3435, 2016.  ACS Nano 7, 4545, 2013.  ACS Nano 7, 2651, 2013.  ACS Nano 8, 9492, 2014.  ACS Nano 8, 7671, 2014.  ACS Nano, 9, 6587, 2015.  Adv. Energy Mater. 3, 1539, 2013.  Adv. Energy Mater. 5, 1500051, 2015.  Adv. Func. Mater. 24, 2620, 2014.  Adv. Energy Mater. 6, 1600237, 2016.  Adv. Func. Mater. 24, 6914, 2014.  Adv. Func. Mater. 10.1002/adfm.201601296.  Nano Energy, 1, 145, 2012
 Nano Energy, 14, 111, 2015.  IEDM, 19.3, 1, 2015
12:00 PM - BM4.2.02
Metallic Nanoislands on Graphene for Cellular Electrophysiology and Wireless, Wearable Sensors
Darren Lipomi 1
1 University of California, San Diego La Jolla United StatesShow Abstract
This paper describes a new class of thin-film mechanical sensor based on metallic nanoislands on graphene. These films are formed by exploiting the characteristic of graphene known as wetting transparency. That is, a thin film formed by an evaporated flux of metal atoms impinging on a graphene surface will adopt a morphology that is largely determined (at nominal thicknesses below approximately 20 nm) by the identity and surface energy of the material supporting the graphene. This control permits the formation of several technologically useful morphologies, among them are disconnected highly crystalline nanoislands that are separated from each other by gaps smaller than 10 nm. The electrical current through these films can be modulated by mechanical strain, which through mechanisms ranging from quantum tunneling at low applied strains to fracture of the graphene at higher strains can exhibit gauge factors over 1000. This sensitivity permits detection of strains ≤0.001%. This talk will describe our efforts to understand the mechanism of formation of these nanoisland-graphene sensors using atomistic dynamics simulations, and the detailed mechanism by which strain modulates the electrical resistance over a large dynamic range, from 0.001% to 10% strain. These sensors can be used to detect the pulse pressure waveform in the radial artery and contractions of stem-cell derived human cardiomyocytes. In another application, strips of these sensors can be bonded to gloves and used to detect the letters of American Sign Language.
12:15 PM - BM4.2.03
Epitaxially Printed Stretchable Sensor with Silver Nanowire Composites
Taeil Kim 1 , Woo Soo Kim 1
1 Simon Fraser University Surrey CanadaShow Abstract
Recent spotlight on wearable electronics generates huge attention on resilient electrodes as stretchable rubber-type electronics. And especially silver nanowire (AgNW)-based composites have been effectively utilized to achieve reliable stretchability as well as qualified conductivity for the stretchable conductor applications. Here we introduce a novel 3D printing technology with capability of electrical property control depending on extruder nozzle’s shape difference, which enables us to print electrically conductive and dielectric parts with the same composition of AgNW in rubber composite. Additionally, the computational simulation for the optimization of 3D conductor depending on highly anisotropic filler’s alignment and distribution has been investigated. The extrusion of rubber composite has been analyzed theoretically by consideration of fluid-mechanical behavior of AgNW fillers in the rubber composites. Computational simulation is also matched well with the experimental result, where AgNWs’ aligned behavior with a round nozzle, and AgNWs’ random distribution with a flat nozzle. Composites with aligned and randomly distributed AgNWs show dielectric and 3D conductive characteristic respectively. Finally, the epitaxially printed stretchable sensors using silicone rubber composite with same concentration of AgNWs have been demonstrated. The fabricated stretchable wireless sensor shows a reliable response to the mechanical strain change by linear change in resonant frequency.
12:30 PM - BM4.2.04
Enabling Highly Stretchable Polymer Semiconductor Films through Nanoconfinement Effect
Jie Xu 1 , Sihong Wang 1 , Jong Won Chung 2 , Zhenan Bao 1
1 Stanford University Stanford United States, 2 Samsung Advanced Institute of Technology Suwon-si Korea (the Republic of)Show Abstract
The lack of stretchable semiconductors has limited the development of stretchable and wearable electronics. All the existing approaches typically sacrifices charge-transport mobility. Here, we present a concept based on nanoconfinement effect of polymers to significantly improve the stretchability of polymer semiconductors, without affecting its charge transport mobility. Our fabricated semiconducting film can be stretched up to 100% strain without affecting its mobility, through which a record-high mobility of 1.32 cm2/Vs has been achieved at 100% strain. Consequently, our fabricated fully stretchable transistor device also has very high stretchability in both directions to the charge transport channel, again measured at a record high mobility value of 0.55 cm2/Vs at 100% strain. We proceed to demonstrate this transistor device as a finger-wearable driver circuit for a LED. Furthermore, this versatile methodology was extended to four other semiconducting conjugated polymers with significant improvement in stretchabilility, which brings the mobilities of three resulting films over 1 cm2/Vs at 100% strain. Because of high versatility on different semiconducting polymers, our nanoconfinement concept could be utilized to impart high stretchability onto any molecular-engineered high-performance conjugated polymers that are developed in the future.
12:45 PM - BM4.2.05
Using Magnetic Fields to Design and Build Transparent, Conducting and Flexible Graphene-Based Composites
Hortense Le Ferrand 1 , Sreenath Bolisetty 1 , Ahmet Demirors 1 , Rafael Libanori 1 , Andre Studart 1 , Raffaele Mezzenga 1
1 ETH Zurich Zurich SwitzerlandShow Abstract
Innovative methods to produce transparent and flexible electrodes are highly demanded in modern optoelectronic and bioelectronic applications, but available solutions suffer from drawbacks such as excessive compliance, prohibitive costs and difficult processability. We propose a simple and highly compatible strategy to produce hierarchically-structured composites of functionalized graphene in polymeric matrices that exhibit high transparency, electron conductivity, and flexibility . Our approach relies on the magnetically-directed assembly of colloidal particles in a fluid that is later converted into a solid composite [2,3]. To this end, we functionalized graphene sheets with protein-assisted attachment of superparamagnetic nanoparticles, to magnetically assemble them directly within matrices undergoing sol-gel transitions. By applying rotating magnetic fields or using specific magnetic virtual moulds, both orientation and local distribution of graphene flakes can be controlled within the composite’s microstructure. Such unique architectural control was confirmed with optical imaging and X-ray scattering techniques. Interestingly, the use of magnetic virtual moulds of predefined meshes allows us to assemble graphene flakes into two independent percolating networks. This results in a significant reduction of the percolation threshold from 1.2 vol% to 0.6 vol% only and enables a combination of optical transparency, electrical conductivity, and flexibility that is not accessible in homogeneously dispersed materials. Indeed, with such optimization of the microstructure, gelatine films of hundreds of micrometer in thickness with 90% transparency and 0.01 S.cm-1 electrical conductivity could be produced. The resulting composites may open new possibilities on the quest of biocompatible transparent electrodes and stretchable optoelectronic sensors: strain resolutions as small as 0.005 % were demonstrated for double percolated composite films under unidirectional compression.
 H. Le Ferrand, S. Bolisetty, A.F. Demirörs, R. Libanori, A.R. Studart, R. Mezzenga, Magnetic assembly of transparent and conducting graphene-based functional composites, Nature Communications. (2016)
 R.M. Erb, R. Libanori, N. Rothfuchs, A.R. Studart, Composites Reinforced in Three Dimensions by Using Low Magnetic Fields, Science. 335 (2012)
 A.F. Demirörs, P.P. Pillai, B. Kowalczyk, B.A Grzybowski, Colloidal assembly directed by virtual magnetic moulds., Nature. 503 (2013)
BM4.3: Neural Interfaces I
Monday PM, November 28, 2016
Hynes, Level 2, Room 207
2:30 PM - *BM4.3.01
Soft Optical Nerve Interfaces for the Peripheral Nervous System
Frederic Michoud 1 , Loic Sottas 1 , Liam Browne 2 , Leonie Asboth 1 , Gregoire Courtine 1 , Clifford Woolf 2 , Stephanie Lacour 1
1 École Polytechnique Fédérale de Lausanne Lausanne Switzerland, 2 Boston Children's Hospital Boston United StatesShow Abstract
Optical stimulation is an alternative to electrical stimulation that promises more selective activation of neurons populations.
We designed and validated a soft opto-cuff, a device that allows for optical stimulation of a peripheral nerve in freely moving mice. The nerve interface is composed of a soft implantable nerve cuff and a tethered ultra-compliant optic fiber further connected to a headstage fixed on the skull.
The opto-cuff is prepared with a 100kPa silicone membrane wrapped around the nerve and coated with a metallic light reflective film to minimize optical losses in the surrounding tissue. The implant was typically 2.5mm long and adjusted to the mouse sciatic nerve diameter.
We demonstrate the soft opto-cuff enables epineural optical modulation of the mouse sciatic nerve without disrupting the animal behavior. We found the compliant cuffs to be well tolerated by the animals and suitable for chronic experiments.
The soft opto-cuff technology offers exciting opportunities to study sensory pathways such as pain.
3:00 PM - BM4.3.02
Subcellular, Ultra-Flexible Nanoelectronic Probes Form Reliable, Glial Scar Free Neural Integration
Lan Luan 1 2 , Xiaoling Wei 1 , Zhengtuo Zhao 1 , Chong Xie 1
1 Department of Biomedical Engineering University of Texas at Austin Austin United States, 2 Department of Physics University of Texas at Austin Austin United StatesShow Abstract
Implanted electrodes provide one of the most important neurotechniques by allowing for acquisition of individual neuron electrical activities in the living brain. However, their recording stability and efficacy in both the short and long term pose limitations on their scientific and clinical applications. Conventional brain probes suffer from substantial recording condition changes in time scales as short as hours due to the micro-movements of the implanted electrodes relative to the brain tissue. Over a period of weeks to months, their recording performance often deteriorates due to sustained foreign body reactions. Here we show that ultra-flexible, subcellular sized brain probe architecture, the nano-electronic thread (NET), forms reliable, glial scar free neural-probe interface, as verified by chronic neural recordings and tissue-probe interface characterizations. We observed that the electrode impedance, the noise level, the single-unit recording yield, and the signal amplitude remain stable during long-term implantation. We demonstrate that individual units can be reliably detected and tracked for months. In vivo two-photon imaging and postmortem histological analysis revealed seamless, subcellular integration of NET probes with the local cellular and vasculature networks. Significantly, we observed fully recovered capillaries with intact blood brain barrier, and complete absence of chronic neuronal degradation and glial scar. The unprecedented chronic reliability and stability is expected to fundamentally advance both basic and applied neuroscience, as well as lead to substantial improvement in brain-machine interface that can be applied to neuroprosthetics. Further, the subcellular dimension probes provide new opportunities for high density electrical recording by overcoming current physical limitations.
3:15 PM - BM4.3.03
Ultra-Thin, Nanoelectronic Coating Devices for Versatile Multimodal Neural Probes
Zhengtuo Zhao 1 , Lan Luan 1 2 , Xiaoling Wei 1 , Chong Xie 1
1 Biomedical Engineering University of Texas at Austin Austin United States, 2 Physics University of Texas at Austin Austin United StatesShow Abstract
In order to develop system-level understanding and control of the highly complex brain activities, extensive efforts have been made to integrate multiple functionalities in neural probes, including simultaneous optical stimulation, drug delivery and high-capacity electrical recording. However, most of demonstrated multimodal neural devices involve highly specialized, high cost fabrication processes and often compromise on overall performance. Here, we present a novel multimodal neural probe platform realised by applying ultra-thin nanoelectronic coating (NEC) on the surface of conventional devices such as optical fibers and micro-pipettes. We fabricated the NEC devices by planar photolithography techniques using a substrate-less and multi-layer design to achieve a total thickness below 1µm and multiple individually addressed electrodes. Guided by an analytic model and taking advantage of surface tension, we attach the NEC device onto and wrap them around the surface of these conventional devices. We demonstrated in mouse model optical stimulation and controlled drug infusion with concurrent electrical recording using the resulted multimodal probes. We also demonstrated great functional versatility enabled by different application-specific electrode patterns on the NEC devices. This study provides a low-cost, versatile and efficient approach to multimodal neural probes that can be useful in both fundamental and applied neuroscience.
3:30 PM - BM4.3.04
Implantable Neural Probes with Ion Pumps for Targeted Drug Delivery#xD;
Christopher Proctor 1 , Adam Williamson 2 , Ilke Uguz 1 , Vincenzo Curto 1 , Sahika Inal 1 , Christophe Bernard 2 , George Malliaras 1
1 Ecole des Mines St Etienne Gardanne France, 2 Aix-Marseille University Marseille FranceShow Abstract
Significant advances have been made in the last two decades in interfacing electronic devices with the nervous system. Organic electronic materials in particular have emerged as ideal materials for interfacing with neurological systems due to their flexibility, biocompatibility and moreover their electronic and ionic conductivity. The ability to conduct ions confers a significant advantage over other electronic materials as organic electronics can in essence communicate in the native language of neurons via ionic currents. To that end, significant research efforts are being pursued to develop minimally invasive, implantable organic electronic devices integrating recording, stimulating, and drug delivery features.
Here we demonstrate multimodal probes with the ability to record and stimulate neurons using low impedance PEDOT:PSS coated electrodes. Furthermore, we show that such devices can also incorporate organic electronic ion pumps for electrophoretic delivery of neurotransmitters with high spatial and temporal resolution. By using a novel vertical ion pump design with a fluidic reservoir along the length of the probe, the voltage needed to pump ions is reduced by more than 10 fold compared to previously reported ion pump platforms. The efficacy of the ion pumps is demonstrated in an epileptic neural network by delivering GABA to stop epileptic behavior. Due to the probes unique biocompatibility and being equipped with high-fidelity organic electronic devices, we anticipate this work to be the starting point for new stimulation, recording and drug delivery paradigms in chronic neural implantation.
3:45 PM - BM4.3.05
Design and Improve Performances on Deep Brain Stimulation (DBS) Electrodes Based on Conducting Polymers
Gaia Tomasello 1 , Prajwal Kumar 1 , Zhang Shiming 1 , Florin Amzica 2 , Fabio Cicoira 1
1 Polytechnique Montreal Montreal Canada, 2 Université de Montréal Montreal CanadaShow Abstract
Neurological degenerative diseases and obsessive-compulsive disorders represent one of the major problems in the public’s health. The development of novel tools devoted to early diagnosis and treatment of these neurological diseases are an important and urgent medical need. In particular, deep brain stimulation (DBS) via implanted intracerebral electrodes that stimulate neurons at different frequencies, is a key technology in neuroprosthetic applications. However, although their adoption for therapeutic treatment is well established, the efficiency and biocompatibility of the probes are far from being ideal . Organic bioelectronics  offers unprecedented opportunities for a novel design of neural electrodes, able to both record and stimulate neurons. Conductive polymers (CP) have emerged as ideal candidates for neurological electrodes, particularly suitable for being interfaced with the nervous tissue. Indeed π-conjugated polymers, besides being mechanically soft, are able to sustain mixed electronic/ionic transport, particularly suitable for interfacing the ionic current in cell membranes. CP-coating on metals  have been already proved to drastically decrease the impedance, required to ensure and maintain an efficient charge injection during stimulation and to improve signal to noise ratio. CP-coated microelectrodes have been further proved to lower the stimulation voltage threshold, resulting beneficial for electrode quality and tissue safety. In our work we have coated DBS microelectrodes made of W and Pt/Ir. We have performed PEDOT:PSS and PEDOT:PF6 electropolymerization exploring different deposition conditions and achieving improved electrical and mechanical performances. The porous morphology of the film have been characterized and measured through Scanning Electron Microscopy (SEM). The electrical performances and stability have been studied using cyclic voltammetry (CV) in aqueous media (Ringer’s solution). Measurements of the temporal frequency-dependent complex impedance have been conducted via Electrochemical Impedance Spectroscopy on conducting polymer coated and bare DBS electrodes within a frequency window of 1.0-105 Hz, according with the range of most interesting neurological processes. In particular, via CP-coating we were able to minimize the magnitude impedance │Z │of the PEDOT-coated electrodes compared with the bare DBS electrodes, thus providing an optimal charge injection achieved with a lower voltage stimulation and more friendly tissue-electrode interface.
 J. Groothuis et al., 2014, Brain Stimulation, 7, 1-6.
 E. Leuthardt et al., 2006, Neurosurgery, 59, 1-16.
 M. Berggren, A. Richter-Dahlfors, 2007, Adv. Mater., 19, 3201-3213.
 D.Martin and G. Malliaras, 2016, ChemElectroChem, 3, 1-4.
BM4.4: Organic Electronic Devices and Applications I
Monday PM, November 28, 2016
Hynes, Level 2, Room 207
4:30 PM - *BM4.4.01
Organic Bioelectronic Networks to Record and Regulate Functions in Animal Models and Plants
Magnus Berggren 1
1 ITN Norrkoping SwedenShow Abstract
Organic bioelectronics is an emerging field of science and technology that promise for novel system tools to record and regulate physiology and functions of biological systems in a highly automated fashion. Here, we report advances in combining organic electronic materials and devices to achieve integrated and distributed circuit systems applied to, implanted into and also manufactured in living systems, in vivo, that sense and deliver relevant biological signals aiming for autoregulation. The nature and characteristics of signalling in biology includes a vast array of ions and chemicals, frequency components ranging from 1 μHz to 10 kHz and a spatial resolution spanning from meters down to sub-micron scales. Our effort aims at establishing a signalling translation technology that bridges the biology-technology signalling gap by developing distributed chemical circuits that perform at the specifications of biological systems and the addressing protocols of traditional electronics. Our goal is to derive a technology for future prosthesis, medical therapy and plant biology applications that also take use of the electrolytic medium of the actual biological system as the communication network.
5:00 PM - BM4.4.02
N-Type Organic Electrochemical Transistors with Stability in Water
Alexander Giovannitti 1 , Christian Nielsen 2 , George Malliaras 3 , Jonathan Rivnay 4 , Iain McCulloch 1
1 Imperial College London London United Kingdom, 2 Queen Mary University of London London United Kingdom, 3 Ecole National Superieure des Mines de Saint-Etienne Gardanne France, 4 PARC Palo Alto United StatesShow 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 the active material, which can be modified by electrochemical redox reactions in aqueous solution (doping/de-doping reactions). OECTs can either be operated in accumulation or depletion mode; operation in accumulation mode has the advantage of lowering the operational voltage. To date, only p-type OECTs, working in both depletion and accumulation mode, have been reported.
We have developed an ambipolar OECT with balanced ambipolar charge transport characteristics. To realize the requirements for stable p- and n-type doping of the active material in aqueous solution, we have prepared conjugated polymers with high electron affinities and low ionisation potentials to allow for efficient doping of the semiconductor at relatively low voltages (vs Ag/AgCl). The electrochemical redox reactions of the polymers were analysed by spectroelectrochemical measurements as well as electric impedance spectroscopy where a capacitance per volume unit (C*) of 397 F/cm3 was measured demonstrating the potential of these materials for bioelectronic applications. Stability measurements were carried out in aqueous solution and a remarkably stable OECT, in operation for over two hours, was achieved without degradation of the active material.
1. Khodagholy, D. et al. High transconductance organic electrochemical transistors. Nat. Commun. 4, 2133 (2013).
2. Inal, S. et al. A High Transconductance Accumulation Mode Electrochemical Transistor. Adv. Mater. 26, 7450–7455 (2014).
5:15 PM - BM4.4.03
Electrolyte-Gated Ferroelectric Biointerfaces
Josefin Nissa 1 , Henrik Toss 1 , Negar Sani 1 , Anurak Sawatdee 2 , David Nilsson 2 , Simone Fabiano 1 , Daniel Simon 1 , Magnus Berggren 1
1 Department of Science and Technology Linköping University Norrköping Sweden, 2 Acreo Swedish ICT Norrköping SwedenShow Abstract
Because of their electrochemical and mechanical properties, conjugated polymers have been identified as a possible bridge between the chemical signalling in our cells and electronic communication used in technology. Organic bioelectronic surfaces can be used to influence cell growth and behaviour by forming gradients and patterns of biomolecules and to induce detachment of cells. Recently, we have added organic ferroelectrics to our collection of organic electronic materials to be used together with biological systems. Ferroelectric materials display a stable polarization, for which the direction can be controlled by the application of an electric field. Once the material has been polarized the polarization is stable. We have shown that the ferroelectric polymer poly(vinylidene-trifluoroethylene) can be polarized through an aqueous electrolyte, offering the possibility to change the surface energy of the polymer while in contact with a biological sample. This makes the ferroelectric materials good candidates for selective adsorption of charged molecules and chemical patterning of surfaces.
5:30 PM - BM4.4.04
Integration of Functional Lipid Bilayers Containing Membrane Proteins on PEDOT:PSS Films and Transistors
Yi Zhang 2 , Sahika Inal 1 , Chih-Hyun Hsia 2 , Magali Ferro 1 , Susan Daniel 2 , Roisin Owens 2
2 Chemical and Biological Engineering Cornell University Ithaca United States, 1 Ecole des Mines-St. Etienne Gardanne FranceShow Abstract
A significant challenge in bioelectronics is an improved understanding of the biotic/abiotic interface. It has been postulated by Fromherz and co-workers that tuning of the gap (or cleft) between a cell and a transducer would allow increased signal transduction of electrical activity of the cell. As a fundamental structure of all biological membranes, lipid bilayers with are widely employed as a model system to investigate interactions between cells and their environment. Interfacing biomimetic lipid bilayers with materials is a much studied problem, and one which can benefit from introduction of novel functional materials, particularly to improve readout of the functionality of the biological systems. The conducting polymer PEDOT:PSS, in particular in its embodiment in the organic electrochemical transistor (OECT), has shown great potential in biosensing applications as it efficiently transduces ionic currents into electronic signals. Mixed ionic/ electronic conduction, along with an ideal biocompatible surface and soft tissue-like mechanical properties, have contributed to the successful use of this material for integration with biological components. We show, for the first time, the assembly of supported lipid bilayers (SLB) on both free-standing PEDOT:PSS films, and OECTs, by vesicle fusion. We further show fusion of blebbed (lipid and protein containing) vesicles from live cells and demonstrate membrane protein functionality. Characterization of lipid bilayers and embedded proteins was carried out using the OECT (electrically), QCM (quartz crystal microbalance) and also via optical techniques (FRAP (fluorescence recovery after photobleaching) and TIRF spectroscopy (total internal reflection fluorescence) thanks to the optical transparency of the conducting polymer films. This work not only shows potential for development of a platform to monitor cellular ion channel activity, but also contributes to our understanding of the interaction of transducers with the outermost surface of cells for future optimization of brain machine interfaces.
 P. Fromherz, Chemphyschem 2002, 3, 276.
 Zhang, Yi, Inal, Sahika, Hsia, chih-hyun, Ferro, Magali, Ferro, Marc, Daniel, Susan, in review. 2016.
5:45 PM - BM4.4.05
Noise and Limit of Detection in Organic Electrochemical Transistors for Biosensing Applications
Ralph Stoop 1 , Michele Sessolo 3 , Kishan Thodkar 1 , Christian Schoenenberger 1 2 , Henk Bolink 3 , Michel Calame 1 2
1 Department of Physics University of Basel Basel Switzerland, 3 Institute of Molecular Science Valencia Spain, 2 Swiss Nanoscience Institute, University of Basel Basel SwitzerlandShow Abstract
Organic electrochemical transistors (OECTs) make use of hydrated conducting polymers which can change their conductivity by reversibly exchanging ions with an electrolyte. Because this working mechanism is favorable for a wide variety of sensing principles in aqueous media, OECTs have been intensively studied in applications such as environmental and physiological monitoring. While much emphasis has been placed on analyzing and maximizing the OECTs signal, a key factor determinant for the sensors performance has been mostly overlooked to date: noise. The major noise source in sensing devices is 1/f noise, which is dominant at low frequencies. Since the binding kinetics of many species of interest in biosensing (e.g. proteins) typically require timescales up to minutes, the 1/f noise becomes a key parameter limiting the performance of the sensor. Low-frequency noise has therefore been studied in depth for several transistor biosensors such as Si nanowires, liquid-gated graphene and single-walled carbon nanotube (SWCNT) transistors. We discuss here the low-frequency noise of OECTs based on the conducting polymer poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonic acid) (PEDOT:PSS). We present the noise scaling behavior with gate voltage, channel dimensions and polymer thickness. We demonstrate that the noise in OECTs scales only inversely with the area of the channel rather than with its volume. These results suggest the use of large area PEDOT:PSS in order to maximize the signal-to-noise ratio (SNR) for biochemical and electrostatic sensing applications. We estimate the characteristic limit of detection (LOD) and SNR of an OECT in a typical ion-sensing measurement, as well as the magnitude of the noise. Comparison with literature shows that the magnitude of the noise in PEDOT:PSS- based OECTs is only slightly larger than that in SWCNTs and Si nanowires devices whereas it is similar to that observed in graphene transistors.
Nick Melosh, Stanford Univ
Woo Soo Kim, Simon Fraser Univ
Rebecca Kramer, Purdue University
George Malliaras, ENSM Saint-Etienne
MilliporeSigma (Sigma-Aldrich Materials Science)
BM4.5: Wearable Sensors and Devices II
Woo Soo Kim
Tuesday AM, November 29, 2016
Hynes, Level 2, Room 207
9:30 AM - *BM4.5.01
E-Skin Apexcardiogram Sensor
Unyong Jeong 1 , Insang You 1
1 Pohang University of Science and Technology Pohang Korea (the Republic of)Show Abstract
Heart disease comes to us without clinical manifestation from time to time. Currently used instruments for cardiac diagnosis such as electrocardiogram (ECG), echocardiogram (ECHO) are limited to temporary check. With the needs of the real-time continuous monitoring, wearable ECG sensors are implemented in these days, but still have difficulty in detecting presymptom of coronary disease or myocardial ischaemia. Several mechanocardiogram have been presented as a promising complementary analysis to ECG. Apex cardiogram (ACG) is a one of representative mechanocardiogram, which monitors the temporal volume of and pressure changes in the heart and through the ACG, hemodynamics of heart can be indirectly monitored. However, ACG had not been commercialized due to its inconvenience and high cost. This study suggests convenient and inexpensive patch type ACG sensor based on emerging electronic skin technology, having possibility of utilization in daily life. The sensor is composed of micro-sized conductive particles. Via rubbing process, the particles could have two-dimensional pattern. The confined conduction paths of particles are varied considerably by applied strain and it induces the sensor to have high sensitivity and accuracy at low strain. Additionally, the sensitivity and measureable strain range can be modulated by changing particle density with modulus of substrate. Through high sensitivity at low strain and large stretchability, the sensor can recognize small palpation at precordium and also bear large strain from body motions. Although further investigation is needed for practical use, the new sensor is a promising tool for mechanocardiac diagnosis, which has limitations with current equipment.
10:00 AM - BM4.5.02
New-Class Strain Sensors for Stretchable Electronics—Novel Device Structures and Eco-Friendly Materials
Lingju Meng 1 , Shicheng Fan 1 , Seyed Milad Mahpeykar 1 , Xihua Wang 1
1 University of Alberta Edmonton CanadaShow Abstract
Flexible and stretchable electronics integrate functional electronic devices on plastic substrates and fill niches complementary to silicon electronics in applications where bending and stretching of devices are required or preferred. Strain sensing is one of the fundamental applications for flexible and stretchable electronics. Here we present our recent efforts to design novel device structure and employ eco-friendly bioplastics for electronic devices. Our devices with nano- and micro-materials and structures show high reproducibility and repeatability, and will enable potential applications in biomedical healthcare.
Nanomaterial-based resistive and capacitive strain sensors have attracted more and more attentions for their applications in artificial skins. Most of these devices provide persistent changes of signals upon human motions. Due to the complexity of materials and system integration, the reproducibility and repeatability are major concerns for further commercialization. For simplifying device design, we proposed a new concept, digital strain sensor, based on the insulating-to-conducting transition of devices through mechanical switching. We fabricated devices with various sensitivities and detection limits by engineering device structures. Further demonstrations of our digital strain sensors were achieved for gesture control and heart-beat monitoring. For the simple design and durable materials, our devices can be reproducibly fabricated and maintain the performance after 10,000 times’ bending.
Biocompatible and biodegradable electronic devices are of interest in biomedical healthcare. Cellulose nanocrystal (CNC) materials, eco-friendly bioplastics, recently attract a great attention in flexible and stretchable electronics. In addition to the unique property of dissolving in water, CNC materials could be applied for future flexible electronics for high tensile strength, low density, low thermal expansion, and non-toxicity. Here we report the first demonstration of using PDMS stencils to pattern metal electrodes on CNC substrates. PDMS stencil lithography prevents the potential damage to the cellulose based flexible substrate, which conventional photolithography process will lead to, without compromising the resolution in patterning. Our strain sensors have high sensitivity with a gauge-factor of over 50 in strain testing, which is the highest among reported strain sensors fabricated on water-soluble substrates.
Lai Y, Ye B, Lu C, Chen C, Jao M, Su W, Hung W, Lin T and Chen Y 2016 Extraordinarily Sensitive and Low-Voltage Operational Cloth-Based Electronic Skin for Wearable Sensing and Multifunctional Integration Uses : A Tactile-Induced Insulating-to-Conducting Transition Adv. Funct. Mater. 26 1286–95
10:15 AM - BM4.5.03
Highly Flexible, OCMFET-Based, Multimodal Tactile Sensors
Andrea Spanu 1 , Fabrizio Antonio Viola 1 , Luigi Pinna 2 , Lucia Seminara 2 , Maurizio Valle 2 , Annalisa Bonfiglio 1 , Piero Cosseddu 1
1 Dept. of Electrical and Electronic Engineering University of Cagliari Cagliari Italy, 2 Dept. of Naval, Electrical, Electronic, and Telecommunications Engineering University of Genova Genova ItalyShow Abstract
Reproducing the human sense of touch with an artificial system is a very challenging task in particular because it involves the capability of fabricating, possibly with the same fabrication technology, different kinds of sensing devices on the same substrate. Moreover, they also have to be fabricated on highly flexible and compliant substrates, as artificial skin patches generally require to be transferred onto complex, possibly 3D, surfaces. Low Voltage Charge Modulated OTFTs (OCMFETs) represents a versatile tool for the realization of a wide range of sensing applications. The architecture is based on a floating gate organic transistor, capable to be operated at low voltages thanks to an ultra-thin, hybrid dielectric. The sensitivity of the device is obtained by anchoring in a part of the floating gate a sensing layer directly exposed to the measurement environment; this sensing layer can be chosen according to the specific external stimulus to be sensed.
In this work we will show that Low Voltage OCMFETs can be fabricated on ultrathin and highly compliant plastic substrates, with a nominal thickness around 1 µm, and employed for the realization of multimodal tactile transducers. In order to achieve sensitivity to pressure, a piezoelectric thin film, namely PVDF, is deposited on the sensing area of the device. In this way, when pressure is applied on the PVDF, the charges induced in the piezoelectric film lead to a variation of transistor threshold voltage and a current variation can be detected as a result of the applied pressure. We will demonstrate that such devices can detect very small pressure, below 300 Pa and can detect forces within a range from 0.01 up to 5 N. A detailed dynamic electromechanical characterization have been carried out, showing that such devices are able to detect dynamic stimuli at a frequency up to 500 Hz. Moreover, being PVDF also a pyroelectric material, temperature variations ranging from 10° up to 45 °C could be also detected. Interestingly, since the responses of the device to the two different physical stimuli are characterized by marked differences in sensitivity and response time, it is possible to employ the same device for the fabrication of multimodal tactile sensing systems. The highly flexibility of the developed structure, and the easiness of the employed process, make this solution very interesting for the fabrication of multimodal, highly compliant artificial skin.
10:30 AM - BM4.5.04
Ultra-Flexible Organic Pulse Oximetry
Tomoyuki Yokota 1 , Peter Zalar 1 , Martin Kaltenbrunner 1 2 , Hiroaki Jinno 1 , Naoji Matsuhisa 1 , Hiroaki Kitanosako 1 , Yutaro Tachibana 1 , Wakako Yukita 1 , Mari Koizumi 1 , Takao Someya 1
1 University of Tokyo Tokyo Japan, 2 Johannes Kepler University Linz AustriaShow Abstract
We have developed an ultra-flexible and conformable, three-color, highly efficient polymer light-emitting diodes (PLEDs) and organic photo detectors (OPDs) to realize pulse oximetry. Optoelectronic devices are especially important in medical field since these devices can non-invasively detect bio singnals and other clinical information. Recently, organic light-emitting diodes (OLEDs) and OPDs were manufactured on glass or bulky (less than 1 mm) plastic substrates and then combined to form a transmission-mode pulse oximeter  and muscle contraction sensor . In previous reports, organic LEDs and photovoltaics were fabricated on 1-µm-thick films, but were driven in nitrogen atmosphere [3, 4].
We report ultra-thin and high-performance PLEDs and OPDs with thin passivation layers. The total thickness of the PLEDs and OPDs, including the substrate and encapsulation layer, is only three micrometers. This value is one order of magnitude thinner than the epidermal layer of human skin. By integrating green and red PLEDs and OPDs, we fabricate an ultra-flexible reflective pulse oximeter.
Three-color PLEDs were manufactured on 1-µm-thick parylene films. The surface of the parylene substrate was planarized by 500-nm polyimide layer. For realizing these optical devices, indium-tin-oxide (ITO) was formed by sputter process. To reduce heat damage to the ultra-flexible substrate, the ITO was formed without substrate heating. Thanks to a reduction of the device thickness (3 µm) and placement of the active layer in the neutral strain position, our ultrathin PLESs and OPDs show the good mechanically flexibility. Our PLEDs wasn’t broken even when bent with a bending radius of 100 µm on the tip of a razor and crumpled.
By integrating ultra-flexible green and red PLEDs with an OPD, a flexible and conformable reflective pulse oximetry has been demonstrated. The pulse oximetry was laminated to skin using adhesive tape with a thickness of 6 mm. The total thickness was approximately 30 µm. In order to detect pulse waves and blood oxygen levels, the device was turned over and wrapped around a finger. While the driving voltage of the PLEDs was set at 5 V, the open-circuit voltage (Voc) of the OPD was monitored to measure the absorption of green and red light in the blood to the pulse.
This work was supported by the Someya Bio-Harmonized ERATO grant.
 C. M. Lochner, Y. Khan,, A. Pierre, and A. C. Arias, Nature Commun. 5 5745 (2014).
 A. K. Bansal, S. Hou, O. Kulyk, E. M. Bowman, and I. D. W. Samuel, Adv. Mater. 27,
 M. S. White, et al., Nature Photonics 7 811–816 (2013).
 M. Kaltenbrunner, et al., Nature Commun. 3 770 (2012).
10:45 AM - BM4.5.05
Template-Free Photoanchoring of Micro-Scale Objects for Manufacturing of Ultra-Miniature Electronic Devices
C. Ryan Oliver 1 , Lillian Chin 1 , David Dellal 1 , Nathan Spielberg 1 , John Lewandowski 1 , A. John Hart 1
1 Massachusetts Institute of Technology Cambridge United StatesShow Abstract
The availability of higher performance microprocessors, communication chips, and inertial sensors with ever smaller dimensions has driven the miniaturization of passive IC components as well as the development of high-throughput surface mount assembly technology. Currently, circuit boards using these components are assembled by mechanical pick and place operations. Further decreases in component size require mutual advances in pick-and-place machine dynamic, component mounting and placement on supply tapes, and micro-scale gripping. Fluidic assembly provides an alternative scalable route to placement of micro-scale objects; however, the requirement for complementary chemistry and/or shape-driven interaction establishes constraints on the process for assembling arbitrary patterns. For these reasons, a flexible process for high-throughput placement of components that overcomes the constraints of pick-and-place assembly is needed.
We present a hybrid manufacturing process for printed electronics, involving inkjet printing of thin-film conductors combined with template-free photo-anchoring of micro-components provided in a continuous flow. To enable template-free anchoring, it was necessary to build the hardware and software that enables real-time imaging of the flow of components over the substrate, image processing, and photopatterning via maskless projection. By this method, software-defined specifications can be used to specify the object placement locations, including for example, the relative positions of each object, dynamic reference points on the substrate (e.g., printed traces where the objects should be placed), selection rules (e.g., object size, orientation, color), and positional tolerances for anchoring. The rate and accuracy of the dynamic anchoring process are studied using polymer beads, and a model is developed to calculate the areal throughput versus the pattern design and image processing performance. Printing accuracies of three pixels (10 μm) on average are demonstrated for beads ranging from 5 to 90 μm. Last, we demonstrate the fabrication of flexible NFC sensing tags, by first inkjet printing Ag antennas on a flexible paper substrate, and subsequently photoanchoring micro-LEDs onto the antenna.
BM4.6: Flexible and Stretchable Electronic Materials II
Tuesday AM, November 29, 2016
Hynes, Level 2, Room 207
11:30 AM - *BM4.6.01
Intrinsically Stretchable Conductors and Thin-Film Transistors
Qibing Pei 1
1 Materials Science and Engineering University of California, Los Angeles Los Angeles United StatesShow Abstract
The development of stretchable electronics and optoelectronics poses fundamental challenges in developing new electronic materials that are mechanically compliant and solution processable. Thin-film field effect transistor (TFT) is a fundamental component behind modern electronic devices including displays, sensor arrays, microprocessers, and identification tags. We report the fabrication of transparent TFTs that behave like an elastomer film while retaining high electronic performance. The transistors are comprised of screen-printed silver nanowires-polyurethane acrylate composite as the gate, source, and drain electrodes, semiconducting single-walled carbon nanotube network channel, and a polyurethane-co-polyethylene oxide dielectric. All these materials are deformable like elastomers. The entire fabrication processes of the stretchable transistors, including the preparation of the source, drain and gate electrodes, semiconductor layer, dielectric layer, and substrate, are all carried out by solution-based techniques under ambient conditions.
12:00 PM - BM4.6.02
Novel Flexible Metal Nanoparticles-Graphene Nanocomposites as Gate Electrodes for Organic Electrochemical Transistor
Carlotta Peruzzi 1 , Giuseppe Tarabella 1 , Sara Pascale 2 , Francesca Rossi 1 , Pasquale D'Angelo 1 , Andrea Secchi 3 , Filippo Fabbri 1 2 , Salvatore Iannotta 1
1 Istituto Materiali per Electronica e Magnetismo Parma Italy, 2 KET Lab Rome Italy, 3 Department of Chemistry University of Parma Parma ItalyShow Abstract
Among the family of Organic Thin Film Transistors (OTFTs), the class of transistors made of electrochemically active polymers are currently of highly interest mainly because of their ability to interface ideally with aqueous environment , mimicking biological systems interfaces. Organic Electrochemical Transistors (OECTs) have been exploited with success as biosensors and transducers in a number of bio-applications, as logic elements and as electrodes for brain interface. With the aim to enhance the selectivity properties of the OECT towards specific bio-molecules, we manufactured a graphene electrode made on a plastic substrate, modified with nanoparticles and used as a gate electrode in an OECT device. As a first step we characterize the OECT response when equipped with the plastic graphene gate modified with different types of nanoparticles. Nanoparticles of Gold (Au) and Silver (Ag) were prepared using a dedicated protocol, with spherical and pyramidal shapes. Transfers characteristics were acquired with two physiological solutions at different molar concentrations. We found an obvious response of the OECT depending on the kind of electrolytes, and interestingly the OECT response depends on the shape of nanoparticle as well as the electrolyte concentration. The transfer curves show a plateaux at low gate voltages, in the range between ~0.2 and ~0.4 V, representing the fingerprint of nanoparticles on the gate surface. The gate voltage shift increases with the increasing of the dimension of nanoparticles. The plateaux of the drain current represents the range of the gate voltage that is not transferred to the electrolyte at the gate/electrolyte interface, representing therefore a special “blind space” where anchoring biomolecules to functionalized nanoparticles.
12:15 PM - BM4.6.03
Acoustophoretic Printing for Stretchable Device
Daniele Foresti 1 2 , Jennifer Lewis 1 2
1 Harvard University Cambridge United States, 2 Wyss Institute Cambridge United StatesShow Abstract
A major need and, at the same time, challenge in additive manufacturing is the ability to pattern materials over a wide range of physical properties. Existing printing techniques have severe limitations inherent to their physical mechanisms, such as narrow range of ink viscosities (e.g., inkjet printing), restrictive ink rheology (e.g. direct ink writing) or limited geometries (e.g., laser induced forward transfer LIFT). As a result, inks must be carefully engineered to match the narrow property range of existing printers. Here we present acoustophoretic printing, in which nonlinear acoustic forces are designed and employed to print drop on demand (DOD) wide range of materials. By controlling these forces, ejected droplet volume can be varied continuously by more than two orders of magnitude, from the nanoliter to microliter range. Specifically, we show that ink viscosities (µ) spanning more than five orders of magnitude (µ =0.5 – 25’000 mPas) can be printed by this method, ranging from food, polymer solutions, cell-laden inks, optical resins, and liquid metals. Such material versatility paves new way in the field of additive manufacturing of stretchable devices. As initial demonstration, we printed bulk eutectic Gallium Indium (eGaIn), patterning conductive lines in a contactless, drop-by-drop fashion. In such a way, simple electronics circuits could be manufactured on stretchable fabrics, without any modification of either the environment or the printed material.
12:30 PM - BM4.6.04
Reversible Elasticity in Ductile or Brittle Thin Films Supported by a Plastic Foil
Nicolas Vachicouras 1 , Christina Tringides 1 , Philippe Campiche 1 , Stephanie Lacour 1
1 Ecole Polytechnique Fédérale de Lausanne Lausanne SwitzerlandShow Abstract
Most electronic materials exhibit limited elasticity. Brittle films display fracture strains of less than about 5%. Ductile films plastically flow at strain larger than 5%. Here, we explore how to engineer reversible elasticity in thin film on plastic substrate using repeated cut patterns through the multilayer structure.
Inspired by the topography of stretchable film gold films on silicone that display dense distributions of Y-shaped cracks to favor out of-plane deformation, we cut Y-shaped motifs throughout the film(s). The motif is characterized by the length of the Y branch a, the distance between two motifs L, and the width of the cut w.
Using a 75µm thick polyimide foil, we prepared macroscopic dog-bone shaped structures with a range of designs: a/L varied from 0.5 to 0.8 and w from 0.7 to 1.5mm. We next recorded the tensile stress (strain) response of the structure to fracture and at 1mm/s strain rate. The structures were also modeled using Finite Element Modeling.
Upon stretching, the polyimide ligaments locally deflect out of plane around the openings, allowing the plastic foil to macroscopically stretch. The effective spring constant of the engineered polyimide can be reduced by two orders of magnitude compared to the plain foil using a/L = 0.8 and w = 1.1mm, nearly matching the spring constant of a silicone elastomer of equivalent thickness (75µm). Moreover, these Y-shaped patterns have no preferential direction of stretching.
Next we applied our design to ductile platinum film on polyimide (PI) foil and brittle ITO (Indium Tin Oxide) film on PET (Polyethylene Terephthalate) foil. We further optimized the Y motif dimensions against the resulting electrical conduction of the film. The conductor macroscopic geometry was 29mm in width, 45mm in length and 100nm in thickness.
The Pt/PI system displayed stable electrical conduction when stretched up to an engineered strain of up to 70%. Moreover, it withstood 100k stretch cycles to 10% applied strain without electromechanical fatigue. Similarly, the ITO/PET structure stretched up to a maximum 50% uniaxial strain, and withstood electrically and mechanically 10k stretch cycle to 10% applied strain.
The proposed design is versatile and compatible with thin-film processing. We anticipate the patterned motifs can be scaled down to offer a wider range of readily elastic electronic materials for applications in stretchable electronics and soft bioelectronics.
12:45 PM - BM4.6.05
Controlled Plastic Deformation as a Means to Achieve Highly Stretchable Polymer Semiconductors
Brendan O'Connor 1 , Tianlei Sun 1 , Joshua Scott 1
1 North Carolina State University Raleigh United StatesShow Abstract
Developing inherently stretchable materials will enable significant advancement in stretchable electronics allowing for seamless transition of traditional device including transistors and optoelectronics into a stretchable platform. Polymer semiconductors are inherently soft materials due to the weak van der Waal intermolecular bonding allowing for flexible devices. However, these materials are not typically stretchable and when large strains are applied they either crack or plastically deform. Here, we study the use of repeated plastic deformation as a means of achieving stretchable films.
In this talk, we will discuss the critical aspects of polymer semiconductor material selection, morphology and interface properties that enable this simple but highly successful approach of achieving stretchable electronic films. We demonstrate that plastic deformation can include both extension and contraction of the film allowing for large repeated deformations of over 75%. During this process we thoroughly characterize the morphology and show that the films follow a well controlled repeated deformation pattern for over 100 stretching cycles. In addition, we show that one can employ high performance donor-acceptor polymer semiconductors that are typically brittle through proper polymer blending. This allows for films that can be stretched over 75% while maintaining charge mobility above 0.1 cm2/Vs throughout the stretching process when applied in a transistor configuration.
BM4.7: Neural Interfaces II
Tuesday PM, November 29, 2016
Hynes, Level 2, Room 207
2:30 PM - *BM4.7.01
Nanoscale Suspended Electrode Arrays for
Scalable Electrophysiology in Small Organisms
Jacob Robinson 1
1 Department of Electrical and Computer Engineering Rice University Houston United StatesShow Abstract
Electrical measurements from cells and synapses in large populations of animals would help reveal fundamental properties of the nervous system and neurological diseases. Small model organisms like worms, hydra, and larvae are ideal for these large-scale studies because they can be manipulated in parallel using microfabricated devices; however, current methods to measure electrical activity in these tiny animals requires low-throughput and invasive dissections. To overcome these limitations we present nano-SPEARs: suspended electrodes that are smaller than a single cell, integrated into a microfluidic device, and able to record electrical activity from intact small animals. Using this technology we have made the first extracellular recordings of body-wall muscle action potentials inside an intact roundworm, Caenorhabditis elegans. By reconfiguring the microfluidic chamber we can use the same technology to record electrical activity from the freshwater cnidarian Hydra littoralis, demonstrating