Loïg Kergoat

A Water‐Gate Organic Field‐Effect Transistor

High-dielectric-constant insulators, organic monolayers, and electrolytes have been successfully used to generate organic field-effect transistors operating at low voltages. Here, we report on a de ...

Advances in organic transistor-based biosensors: from organic electrochemical transistors to electrolyte-gated organic field-effect transistors.

AbstractOrganic electronics have, over the past two decades, developed into an exciting area of research and technology to replace classic inorganic semiconductors. Organic photovoltaics, light-emitting diodes, and thin-film transistors are already well developed and are currently being commercialized for a variety of applications. More recently, organic transistors have found new applications in the field of biosensors. The progress made in this direction is the topic of this review. Various configurations are presented, with their detection principle, and illustrated by examples from the literature. FigureElectrolyte-Gated OFET (EGOFET) architecture. EGOFETs differ from OFETs, as in OECTs, in that the gate is separated from the semiconductor by an electrolyte. This allows low voltage operation compared with OFETs gated via solid dielectrics. The red circle indicates the interface involved in the detection of biomolecules, when water is used as electrolyte.

Detection of Glutamate and Acetylcholine with Organic Electrochemical Transistors Based on Conducting Polymer/Platinum Nanoparticle Composites

The aim of the study is to open a new scope for organic electrochemical transistors based on PEDOT:PSS, a material blend known for its stability and reliability. These devices can leverage molecular electrocatalysis by incorporating small amounts of nano-catalyst during the transistor manufacturing (spin coating). This methodology is very simple to implement using the know-how of nanochemistry and results in efficient enzymatic activity transduction, in this case utilizing choline oxidase and glutamate oxidase.

Controlling Epileptiform Activity with Organic Electronic Ion Pumps

In treating epilepsy, the ideal solution is to act at a seizures onset, but only in the affected regions of the brain. Here, an organic electronic ion pump is demonstrated, which directly delivers on-demand pure molecules to specific brain regions. State-of-the-art organic devices and classical pharmacology are combined to control pathological activity in vitro, and the results are verified with electrophysiological recordings.

Tuning the threshold voltage in electrolyte-gated organic field-effect transistors

Low-voltage organic field-effect transistors (OFETs) promise for low power consumption logic circuits. To enhance the efficiency of the logic circuits, the control of the threshold voltage of the transistors are based on is crucial. We report the systematic control of the threshold voltage of electrolyte-gated OFETs by using various gate metals. The influence of the work function of the metal is investigated in metal-electrolyte-organic semiconductor diodes and electrolyte-gated OFETs. A good correlation is found between the flat-band potential and the threshold voltage. The possibility to tune the threshold voltage over half the potential range applied and to obtain depletion-like (positive threshold voltage) and enhancement (negative threshold voltage) transistors is of great interest when integrating these transistors in logic circuits. The combination of a depletion-like and enhancement transistor leads to a clear improvement of the noise margins in depleted-load unipolar inverters.

Bioelectronic neural pixel: Chemical stimulation and electrical sensing at the same site

Significance Electronically and ionically conducting polymers provide a unique means to translate electronic addressing signals into chemically specific and spatiotemporally resolved delivery, without fluid flow. These materials have also been shown to provide high-fidelity electrophysiological recordings. Here, we demonstrate the combination of these qualities of organic electronics in multiple 20 × 20 µm delivery/sensing electrodes. The system is used to measure epileptic activity in a brain slice model, and to deliver inhibitory neurotransmitters to the same sites as the recordings. These results show that a single-cell-scale electrode has the ability to both record and chemically stimulate, demonstrating the local effects of therapeutic treatment, and opening a range of opportunities in basic neuroscience as well as medical technology development. Local control of neuronal activity is central to many therapeutic strategies aiming to treat neurological disorders. Arguably, the best solution would make use of endogenous highly localized and specialized regulatory mechanisms of neuronal activity, and an ideal therapeutic technology should sense activity and deliver endogenous molecules at the same site for the most efficient feedback regulation. Here, we address this challenge with an organic electronic multifunctional device that is capable of chemical stimulation and electrical sensing at the same site, at the single-cell scale. Conducting polymer electrodes recorded epileptiform discharges induced in mouse hippocampal preparation. The inhibitory neurotransmitter, γ-aminobutyric acid (GABA), was then actively delivered through the recording electrodes via organic electronic ion pump technology. GABA delivery stopped epileptiform activity, recorded simultaneously and colocally. This multifunctional “neural pixel” creates a range of opportunities, including implantable therapeutic devices with automated feedback, where locally recorded signals regulate local release of specific therapeutic agents.

A Static Model for Electrolyte-Gated Organic Field-Effect Transistors

We present a dc model to simulate the static performance of electrolyte-gated organic field-effect transistors. The channel current is expressed as charge drift transport under electric field. The charges accumulated in the channel are considered being contributed from voltage-dependent electric-double-layer capacitance. The voltage-dependent contact effect and short-channel effect are also taken into account in this model. A straightforward and efficient methodology is presented to extract the model parameters. The versatility of this model is discussed as well. The model is verified by the good agreement between simulation and experimental data.

Ferroelectric polarization induces electronic nonlinearity in ion-doped conducting polymers

Ferroelectric-coated counter electrodes control the electrochemistry of conducting polymers. Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is an organic mixed ion-electron conducting polymer. The PEDOT phase transports holes and is redox-active, whereas the PSS phase transports ions. When PEDOT is redox-switched between its semiconducting and conducting state, the electronic and optical properties of its bulk are controlled. Therefore, it is appealing to use this transition in electrochemical devices and to integrate those into large-scale circuits, such as display or memory matrices. Addressability and memory functionality of individual devices, within these matrices, are typically achieved by nonlinear current-voltage characteristics and bistability—functions that can potentially be offered by the semiconductor-conductor transition of redox polymers. However, low conductivity of the semiconducting state and poor bistability, due to self-discharge, make fast operation and memory retention impossible. We report that a ferroelectric polymer layer, coated along the counter electrode, can control the redox state of PEDOT. The polarization switching characteristics of the ferroelectric polymer, which take place as the coercive field is overcome, introduce desired nonlinearity and bistability in devices that maintain PEDOT in its highly conducting and fast-operating regime. Memory functionality and addressability are demonstrated in ferro-electrochromic display pixels and ferro-electrochemical transistors.

Solution processed liquid metal-conducting polymer hybrid thin films as electrochemical pH-threshold indicators

A global and accurate mapping of the environment could be achieved if sensors and indicators are mass-produced at low cost. Printed electronics using polymeric (semi)conductors offer a platform for such sensor/indicator based circuits. Herein, we present the material concept for an electrochemical pH-threshold indicator based on a printable hybrid electrode which comprises a liquid metal alloy (GaInSn) embedded in a conducting polymer matrix (PEDOT). This hybrid electrode displays a large variation in open circuit potential versus pH in an electrochemical cell, which when connected to the gate of an electrochemical transistor leads to a dramatic change in the drain current in a narrow range of pH.

Transient analysis of electrolyte-gated organic field-effect transistors

A terminal charge and capacitance model is developed for transient behavior simulation of electrolyte-gated organic field effect transistors (EGOFETs). Based on the Ward-Dutton partition scheme, the charge and capacitance model is derived from our drain current model reported previously. The transient drain current is expressed as the sum of the initial drain current and the charging current, which is written as the product of the partial differential of the terminal charges with respect to the terminal voltages and the differential of the terminal voltages upon time. The validity for this model is verified by experimental measurements.