Microfabrication of Organic Electrochemical Transistors for High‐Performance Integrated Bioelectronics

Abstract In bioelectronics, organic electrochemical transistors (OECTs) are pivotal in bridging electronic devices and biological systems, especially in sensing, neuromorphic interfacing, and biological monitoring. Current OECT fabrication methods face challenges due to conductive polymers incompatibility with photoresist solvents and the complexity of multi‐step parylene‐C coatings. This work introduces a scalable photolithographic fabrication process for high‐performance OECTs using the prototypical conductive polymer poly(3,4‐ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS). The method employs a two‐layer photoresist approach with controlled cross‐linking, incorporating (3‐glycidyloxypropyl)trimethoxysilane to pattern polymeric channel and encapsulate electrodes. This process yields high‐performance OECTs with highly reproducible characteristics, typical ON/OFF current modulation of 5 10 3 , and transconductance normalized to channel thickness > 200 S cm −1 . To avoid cytotoxic Ag/AgCl pellets, the impact of scaling polarizable gates is analyzed on device performance, including bare Au, protein‐functionalized, and PEDOT:PSS gates. The analysis provides design rules to tailor OECT performance for diverse applications. The effectiveness of the approach is demonstrated by integrating OECTs with polarizable gates in current‐driven circuit configuration, allowing ion detection at a supply voltage as low as 0.4 V with a sensitivity of up to 2620 mV dec −1 , the highest ever reported. These advancements open opportunities for next‐generation integrated bioelectronics and neuromorphic biosensing.