High specificity real-time ascorbic acid detection in human sweat using a flexible PEDOT:PSS-based organic electrochemical transistor

Human sweat offers critical physiological insights, fueling the development of wearable sweat sensors. Ascorbic acid (AA), a vital nutrient, requires precise monitoring in sweat to assess dietary and health status. Organic electrochemical transistors (OECTs) are promising for detecting redox-active molecules like AA due to their high sensitivity, low operating voltage, and aqueous compatibility. However, conventional OECTs, such as those with gold gate electrodes, struggle to selectively distinguish AA from molecules with similar redox potentials (e.g., dopamine, uric acid). To address this, we developed a novel, fully PEDOT:PSS-based flexible OECT with a polypyrrole-based molecularly imprinted polymer (PPy-MIP) on the gate electrode, electropolymerized with AA as the template to create highly selective AA-specific cavities. The PPy-MIP not only ensures selective AA capture but also catalyzes its oxidation, modulating channel current with a wide linear range (10–1000 μM), high sensitivity (46 % channel current change per decade), and an ultralow detection limit (50 nM). The sensor exhibits superior specificity, resisting interference from 100 μM uric acid, urea, glucose, and dopamine. Its flexible design, with minimal performance deviation (<0.85 % at 3 cm bending radius), enables reliable, non-invasive, real-time AA monitoring in sweat, surpassing clinical requirements and advancing personalized healthcare with a cost-effective, skin-conformable platform.