Biocompatible Solid‐State Ion‐Sensitive Organic Electrochemical Transistor for Physiological Multi‐Ions Sensing

Abstract

Wearable bioelectronic sensors have gained tremendous prominence and applicability in healthcare technologies as they offer an alternative to traditional clinical testing and health monitoring. However, many challenges must be overcome for off‐site and point‐of‐care commercial applications, including sensitivity, selectivity, multiple analyte detection, sample procurement technique, invasiveness, biocompatibility, and accurate real‐time sensing. Specifically, a wearable sweat‐based diagnostic biosensing platform offers a noninvasive way for rapid and real‐time monitoring of various physiological biomarkers. This work develops a flexible solid‐state organic electrochemical transistor with an extended sensing node for multi‐ions sensing in the physiological range with high selectivity, fast response, and superior sensitivity. The solid‐contact architecture is implemented for easy sample handling, processability, device miniaturization, and flexibility. For the first time, multiplexed ions (sodium (Na+), potassium (K+), and calcium (Ca2+)) sensing with the integration of ion‐selective membranes and biocompatible semiconducting channel in an extended gate‐solid‐state organic electrochemical transistor (ExG‐SSOECT) is presented. The integrated ExG‐SSOECT device platform exhibits improved performance among the available wearable sensors and offers great potential to be a suitable biochemical sensor in wearable bioelectronics.

Guidelines on Measuring Volumetric Capacitance in Organic Electrochemical Transistors

“…As shown in Figure a at V G = +0.6 V, an off current on the order of 1 × 10 –6 A was recorded, resulting in an on/off ratio of approximately 10 2 . This is consistent with the state-of-the-art performance of PEDOT:PSS-based OECTs with aqueous electrolytes. − The maximum transconductance, as depicted in the red-dashed curve in Figure b, was measured at 2.3 ± 0.8 mS for V D = −0.4 V and V G = −0.075 V. Given that g m = Wd / L μ C *­( V T – V G ), the calculated μ C * was 118.7 F cm –1 V –1 s –1 , in line with the typical performances of PEDOT:PSS-based OECTs reported in the early literature. ,,,, …”

“…18−21 The maximum transconductance, as depicted in the red-dashed curve in Figure 2b, was measured at 2.3 ± 0.8 mS for V D = −0.4 V and V G = −0.075 V. Given that g m = Wd/LμC*(V T − V G ), 11 the calculated μC* was 118.7 F cm −1 V −1 s −1 , in line with the typical performances of PEDOT:PSS-based OECTs reported in the early literature. 7,11,13,20,22 Note that the figure of merit provides a straightforward method for obtaining the electronic mobility of the OECTs, avoiding the need for complex measurements and experimental setup. Once μC* is directly derived from the transconductance, knowledge of the device's capacitance allows for the calculation of the electronic mobility.…”

“…Organic electrochemical transistors were first introduced in 1984 by White et al However, it was not until the late 2000s that the potential of these devices started gaining recognition by the scientific community for their useful range of applications, including biosensors, neuromorphic devices, and logical computing, − to name a few. Indeed, significant progress has been made over the years, starting in the mid-2000s, especially regarding their basic and fundamental operation mechanisms.…”

Materials aspects of PEDOT:PSS for neuromorphic organic electrochemical transistors

“…All of these applications exploit ion diffusion in the PEDOT:PSS layer. For instance, some biomolecular sensing devices are based on the perturbation of ion injection in the presence of target molecules [30][31][32]. As mentioned below, neuromorphic applications also control ion diffusion via ion trapping or ion diffusivity tuning [33][34][35][36][37][38].…”

Development of Screen-Printed Biodegradable Flexible Organic Electrochemical Transistors Enabled by Poly(3,4-ethylenedioxythiophene) Polystyrene Sulfonate and a Solid-State Chitosan Polymer Electrolyte

“…6 In OECTs, a small input gate voltage (V G ) can be converted into substantial variations in the drain current (I D ) with very high transconductance (g), 7 which characterizes OECTs with low voltage operation, 8 high amplification, 9 and biological environment compatibility. 10 Thus, OECTs are being prospected for numerous applications, including biological neural interfaces, 11 biological and chemical sensors such as electrophysiology, 12,13 biomolecule sensing, 14 barrier tissues sensing, 15 and recently COVID-19 detection. 16 However, the use of aqueous electrolytes in OECTs introduces challenges like fluidity, requiring a robust protective layer to prevent swelling in the channel.…”