Fully Solution-Processed Organic Electrochemical Transistors with Nafion/Chitosan-Coated Gates for Enhanced Cation Detection and Scalable Production

Abstract Organic electrochemical transistors (OECTs) represent a promising platform for ion sensing applications due to their unique volumetric doping mechanism and biocompatibility. However, achieving enhanced cation detection while maintaining scalable and cost-effective fabrication remains a significant challenge, limiting their practical deployment. Here, an all-solution approach that integrates ion-responsive polymer coatings on silver gate electrodes to address both sensitivity and manufacturability concerns is presented. Our fabrication strategy employs screen-printing techniques exclusively on flexible polyethylene terephthalate substrates, utilizing cross-linked poly(3-hexylthiophene) channels and strategically modified gate electrodes with Nafion or chitosan coatings. Nafion-coated devices demonstrate superior performance with twice transconductance enhancement from 3.2 to 6.6 mS and dramatically reduce charge-transfer resistance from 30 to 2.3 kΩ, enabling enhanced cation response across 10–5 to 1 M concentrations while maintaining excellent resistance to neutral organic interferents. Chitosan-modified electrodes achieve the fastest temporal response with 3 times faster recovery times. The devices exhibit robust reproducibility and stability, with negligible interference from common neutral organic solvents including ethanol, acetone, and hexane. This scalable platform opens possibilities for industrial-scale production of disposable biosensors, particularly for point-of-care medical diagnostics and environmental monitoring applications requiring cost-effective, high-performance ion detection.