A reusable, wireless, battery-free, non-invasive sweat cortisol sensor

The profound impact of stress on health underscores the need for precise and objective measurement techniques, as traditional self-report questionnaires often fall short in reliability. Molecular biosensors, especially those targeting cortisol—a critical stress hormone—offer a compelling alternative. This study presents an innovative wearable sensing system that utilizes a molecularly imprinted polymer-radiofrequency (MIP-RF) mechanism for non-invasive, real-time cortisol detection in sweat. The system is designed to be wireless, flexible, battery-free, reusable, and environmentally stable, ideal for long-term use with an inductance-capacitance transducer that translates cortisol levels into resonant frequency shifts with high sensitivity within a physiological range of 0-1μM. The device is further enhanced with NFC for seamless, battery-free operation and a 3D-printed microfluidic channel for direct sweat collection, facilitating continuous cortisol monitoring during daily activities. Validation through circadian rhythm tracking, which compares morning and evening cortisol levels, confirms its effectiveness for precise molecular stress biomarker detection.