Adaptive VOC detection with alcohol dehydrogenase-integrated gelatin transistors

Abstract

Accurate detection of ethanol vapor, a representative volatile organic compound (VOC), is of critical importance for environmental safety, industrial hygiene and healthcare diagnostics. In this study, we present an enzyme-doped gelatin-based organic electrochemical transistor (OECT) that enables real-time ethanol-responsive sensing through enzyme-mediated adaptive signal modulation. The sensor design features a bioinspired gelatin bilayer integrated onto the gate electrode of a PEDOT:PSS OECT. The top gelatin layer (Gelatin B) is functionalized with alcohol dehydrogenase (ADH), which catalyzes ethanol oxidation and drives localized NADH/NAD+ redox cycling. This enzymatic reaction alters the interfacial charge environment, influencing the ionic transport within the underlying KOH-modified gelatin layer (Gelatin A) and dynamically tuning the PEDOT:PSS channel conductivity. To further enhance charge redistribution, a PVDF:[BMIM][TFSI] ion gel is incorporated into the device structure. Surface morphology and optical properties were validated using atomic force microscopy (AFM) and UV-Vis spectroscopy, respectively. The sensor was fabricated on a flexible polyimide substrate via screen printing, enabling compatibility with wearable platforms. Ethanol vapor exposure elicited synaptic-like behavior, including cumulative response under prolonged exposure, reminiscent of olfactory adaptation. Paired-pulse facilitation (PPF) and long-term memory retention confirmed the device's neuromorphic characteristics. This platform offers a modular and scalable strategy for VOC detection, where enzyme selection can be tailored for specific analytes. The combination of biological recognition and electronic transduction establishes a promising route toward next-generation wearable gas sensors.