Battery-free wireless stretchable wearable sweat sensor with ion-driven optical signal transduction and chip-level discrete components

Continuous wearable monitoring of sweat electrolytes can provide valuable insights into human metabolic dynamics. Existing strategies usually rely on integrated chips and complicated signal transductions, which is power consuming and limits wearable applications. Herein, we developed a wireless and battery-free stretchable sensor for the detection of multiple electrolytes in sweat simultaneously. Ion-selective electrodes and junction field-effect transistors (JFETs) were integrated for the converting of electrode potential changes triggered by sweat ion concentration variations into JFET channel current changes, of which the signal could be read out through the brightness changes of light-emitting diodes (LEDs). This sensor exhibits high sensitivity and linear responses in the ranges of 1–32 mM for K⁺, 5–160 mM for Na⁺, and 4–8 for pH. Leveraging a self-designed fast image processing algorithm, the detection accuracy is comparable to that of traditional standard instruments, ensuring the practicality of wearable applications. Notably, the sensor is ultra-low-power consumption, with a peak power of only 24.5–31.5 mW. By integrating microfluidic chips and fully elastic near field communication (NFC) power supply antenna, the full-process wearable detection strategy is achieved. Based on the correlation between sweat electrolytes and human health, this sensor presents an on-site detection platform with high accuracy and ultra-low-power consumption, providing a solution for health management accessible to families.