Adhesive Cutaneous Conducting Polymer Electrodes

Conducting polymers are widely used as electrode coatings in electrophysiology to lower impedance and achieve higher quality recordings and more efficient stimulation. Their availability as dispersions that can be processed directly from solution makes them particularly attractive for applications where low cost and compatibility with mechanically flexible substrates are important. In this work we demonstrate that poly(3,4-ethylenedioxythiophene)-based conducting polymer films can be made adhesive to skin and polyimide by adding acrylic ester copolymer microparticles to the solution. The resultant films remained highly conducting despite incorporating at most 2.5% conducting polymer. We show that adhesive cutaneous electrodes fabricated using these coatings show comparable performance to commercial electrodes in forearm electromyography

Microfabricated Ion-Selective Transistors with Fast and Super-Nernstian Response

Transistor-based ion sensors have evolved significantly, but the best-performing ones rely on a liquid electrolyte as an internal ion reservoir between the ion-selective membrane (ISM) and the channel. This liquid reservoir makes sensor miniaturization difficult and leads to devices that are bulky and have limited mechanical flexibility, which is holding back the development of high-performance wearable/implantable ion sensors. This work demonstrates microfabricated ion-selective organic electrochemical transistors (OECTs) with a transconductance of 4 mS, in which a thin polyelectrolyte film with mobile sodium ions replaces the liquid reservoir. These devices are capable of selective detection of various ions with a fast response time (~1 s), a super-Nernstian sensitivity (85 mV dec-1) and a high current sensitivity (224 µA dec-1), comparing favorably to other ion sensors based on traditional and emerging materials. Furthermore, the ion-selective OECTs are stable with highly reproducible sensitivity even after 5 months. These characteristics pave the way for new applications in implantable and wearable electronics

Organic electronics for neuromorphic computing

Neuromorphic computing could address the inherent limitations of conventional silicon technology in dedicated machine learning applications. Recent work on silicon-based asynchronous spiking neural networks and large crossbar-arrays of two-terminal memristive devices has led to the development of promising neuromorphic systems. However, delivering a compact and efficient parallel computing technology, such as artificial neural networks embedded in hardware, remains a significant challenge. Organic electronic materials offer an attractive alternative for such systems and could provide biocompatible and relatively inexpensive neuromorphic devices with low-energy switching and excellent tunability. Here, we review the development of organic neuromorphic devices. We consider different resistance switching mechanisms, which typically rely on electrochemical doping or charge trapping, and discuss the challenges the field faces in implementing low power neuromorphic computing, which include device downscaling, improving device speed, state retention and array compatibility. We highlight early demonstrations of device integration into arrays and finally consider future directions and potential applications of this technology

Energetic disorder at the metal/organic semiconductor interface

The physics of organic semiconductors is dominated by the effects of energetic disorder. We show that image forces reduce the electrostatic component of the total energetic disorder near an interface with a metal electrode. Typically, the variance of energetic disorder is dramatically reduced at the first few layers of organic semiconductor molecules adjacent to the metal electrode. Implications for charge injection into organic semiconductors are discussed.Comment: 9 pages, 2 figure

Transient behavior of photorefractive gratings in a polymer

The transient behavior of photorefractive gratings in the polymer composite poly(N-vinyl carbazole) (PVK), 2,4,7-trinitro-9-fluorenone (TNF), and N,N-diethyl-para-nitroaniline (EPNA) doped with various amounts of 4-(diethylamino)benzaldehyde diphenylhydrazone (DEH) is presented. The influence on the hole drift mobility due to the change in the trap density induced by DEH, was directly measured. (C) 1995 American Institute of Physics

Conducting Polymer Scaffolds based on PEDOT and Xanthan Gum for Live-Cell Monitoring

Conducting polymer scaffolds can promote cell growth by electrical stimulation, which is advantageous for some specific type of cells such as neurons, muscle or cardiac cells. As an additional feature, the measure of their impedance has been demonstrated as a tool to monitor cell-growth within the scaffold. In this work, we present an innovative conducting polymer porous scaffolds based on poly(3,4-ethylenedioxythiophene) (PEDOT):xanthan gum instead of the well-known PEDOT:polystyrene sulfonate scaffolds. These novel scaffolds combine the conductivity of PEDOT, and the mechanical support and biocompatibity provided by a polysaccharide, xanthan gum. For this purpose, first the oxidative chemical polymerization of EDOT was carried out in the presence of polysaccharides leading to stable PEDOT/xanthan gum aqueous dispersions. Then by a simple freeze drying process porous scaffolds were prepared from these dispersions. Our results indicated that the porosity of the scaffolds and mechanical properties are tuned by the solids content and formulation of the initial PEDOT:polysaccharide dispersion. Scaffolds showed interconnected pore structure with tunable sizes ranging between 10 to 150 μm and Young’s moduli between 10 to 45 kPa. These scaffolds successfully support 3D cell cultures of MDCK II eGFP and MDCK II LifeAct epithelial cells, observing good cell attachment with very high degree of pore coverage. Interestingly, by measuring the impedance of the synthesized PEDOT scaffolds, the growth of the cells could be monitored

Roughness-induced energetic disorder at the metal/organic interface

The amplitude of the roughness-induced energetic disorder at the metal/organic interface is calculated. It was found that for moderately rough electrodes, the correction to the electrostatic image potential at the charge location is small. For this reason, roughness-induced energetic disorder cannot noticeably affect charge carrier injection, contrary to the recent reports.This work was supported by the ISTC Grant No. 2207 and RFBR grants 05-03-33206 and 03-03-33067. The research described in this publication was made possible in part by Award No. RE2-2524-MO-03 of the U.S. Civilian Research & Development Foundation for the Independent States of the Former Soviet Union (CRDF)

Stability of PEDOT:PSS-Coated Gold Electrodes in Cell Culture Conditions

Poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS) is widely used as a coating on microelectrode arrays in order to reduce impedance for both in vitro and in vivo electrophysiology. In many applications, electrode performance of months to years is desired; yet, there are few studies to date that examine the long-term stability of conducting polymers and their devices. Here, the stability of PEDOT:PSS microelectrodes is examined over a period of four months in cell culture media enriched with fetal bovine serum. The electrochemical impedance remains constant for most electrodes throughout the study, and only small changes in the structure of functional electrodes are observed at the end of the test. The results demonstrate that PEDOT:PSS electrodes show adequate stability for a variety of in vitro electrophysiology applications in toxicology, drug development, tissue engineering, and fundamental studies of electrically active cells and tissues.A.L.R. acknowledges support from the Whitaker International Scholars Program and the European Commission’s Horizon 2020 Marie Sklodowska-Curie Individual Fellowship BRAIN CAMO (No. 797506). G.D. acknowledges support from the European Commission through the project of OrgBIO-ITN 607896

Performance of a polymer light-emitting diode with enhanced charge carrier mobility

The device characteristics of a polymer light-emitting diode (PLED) based on a poly(p-phenylene vinylene) (PPV) derivative with an enhanced charge carrier mobility have been investigated. Improvement of the mobility, which has been obtained by a decrease of the energetic disorder in the polymer, is expected to increase the power efficiency of a PLED. However, it is demonstrated that an increased mobility leads to a decrease as well as to a slower rise of the quantum efficiency with voltage. This performance reduction is explained in terms of an increased quenching of the electroluminescence (EL) at the cathode.