Wearable organic-electrochemical-transistor-based lithium sensor for precision mental health

Mental health disorders, including bipolar disorder, pose significant challenges worldwide, necessitating precise monitoring of lithium, a gold-standard medication for this condition. We introduce a fully-printed, wearable Organic-Electrochemical-Transistor (OECT)-based sensor for non-invasive and continuous monitoring of lithium levels in sweat. This sensor integrates inkjet and 3D printing to fabricate multilayer OECTs with an ion-selective membrane, alongside iontophoretic sweat induction and microfluidic guidance for real-time sensing. Our sensor demonstrates sensitivity of ΔI _ds /I ₀ = 0.5/decade, a 0.1 mM detection limit in artificial sweat and selectivity for lithium over common interfering ions. A complete wearable system with wireless readout enables real-time data transmission to a smartphone interface. Validation in both healthy individuals and bipolar patients confirms the device's ability to detect therapeutically significant lithium levels. This report provides a promising path for precision mental health management, presenting a first-of-its-kind wearable real-time monitoring solution for lithium-a vital medication in treating bipolar disorder.