High‐Performance Internal Ion‐Gated Organic Electrochemical Transistors for High‐Frequency Bioimpedance Analysis

Abstract

Internal ion‐gated organic electrochemical transistor (IGT) demonstrates volume‐dependent transconductance with the unprecedented advantages of high speed and self‐(de)doping capability among ion‐based transistors. The novel characteristics have albeit rendered IGT a promising platform for integrated bioelectronics, its potential in high‐frequency applications has yet been fully harnessed. Moreover, a study from a material's point of view is especially needed for this recently emerged platform as the necessity of maintaining the internal ion reservoir has posed difficulties in processing hydrated poly(3,4‐ethylenedioxythiophene) doped with poly(styrene sulphonate) (PEDOT:PSS) with electronically favorable morphologies. Herein, a comprehensive investigation of the structural and functional properties of ion‐embedded PEDOT:PSS modified by different annealing temperatures is performed and correlated to the IGT performance. A short‐time high‐temperature annealing treatment is found effective in facilitating the formation of compact microstructures without significantly influencing film hydration. The structural improvement enhances the film's conductivity and hole mobility, with the corresponding IGTs exhibiting higher gain, higher conductance, and high cut‐off frequency consistently in a batch. This study also successfully demonstrates the first use of electrochemical transistors like IGTs in high‐frequency applications through proof‐of‐concept experiments simulating fluid estimation in 50 kHz bioimpedance analysis. This work contributes to the development of high‐performance IGTs for extensive biological applications.

Device design principles and bioelectronic applications for flexible organic electrochemical transistors

“…And table 2 summarizes the characteristics of the abovementioned four kinds of OECT geometries. In addition to these structures, a biocompatible, adaptable, stable, high-speed, and highly conductive internal ion-gated organic electrochemical transistor (IGTs) structure has also been proposed for integrated bioelectronics applications [96,97]. IGTs embedded electrolytes ions into the conducting polymer of the transistor channel, creating a self-(de)doping process that eliminates the need to exchange ions from a shared external electrolyte.…”

“…As described above in the section on working mechanism, a gate electrode with efficient gating ability is crucial for realizing excellent transconductance performance. In general, PEDOT: PSS-modified gold and non-polarized Ag/AgCl are commonly used as gates [96]. In addition, conductive polymer (PEDOT: PSS) and carbon material (graphene and carbon nanotubes) have also been explored as gate materials in flexible OECTs [100,101], and the OECT electrochemical performance based on traditional and novel gate materials depends on the specific application requirements and the specific material used.…”

A photo-responsive organic electrochemical transistor

“…16,17 During the past decade, the bioelectronics endeavor has mainly been focused on the figures of merit of OECTs, such as transconductance, 18 reaching performances that make such devices suitable for functional applications. 19 Molecular doping strategies in organic materials have been continuously improved towards the development of reliable electronics. 20 Yet, device stability needs further optimisation, 21 due to the special environment of living systems, and more testing both in bioelectronic circuits 22 and for in vivo applications is required.…”

“…devices suitable for functional applications. 19 Molecular doping strategies in organic materials have been continuously improved towards the development of reliable electronics. 20 Yet, device stability needs further optimisation, 21 due to the special environment of living systems, and more testing both in bioelectronic circuits 22 and for in vivo applications is required.…”

Laser‐Induced Graphene Electrodes for Organic Electrochemical Transistors (OECTs)

“…However, it has drawbacks such as the price of indium, its difficulty to be printed on flexible substrates, and its brittleness which leads to a sharp decrease in the electrical conductivity with bending. [16] The noble metals gold [17][18][19] palladium [20] and platinum [21] have long been considered among the best metals for source and drain electrodes due to their high conductivity, stability, and well-matched work function, but a major drawback is their high cost.…”