Battery‐Free and Wireless Epidermal Electrochemical System with All‐Printed Stretchable Electrode Array for Multiplexed In Situ Sweat Analysis

Abstract Skin‐interfaced electrochemical sensing devices are widely developed for biochemical sensing at molecular levels. However, the sensing electrodes fabricated with photolithography or printing technique are hard to achieve high stretchability without special designs like serpentine shape. Also, most of them require wired connections with external electrochemical workstations for data acquisition or on‐board batteries to power the circuits, which largely restrain the flexibility, simplification, and miniaturization of the devices. Here, a battery‐free, wireless, and epidermal electrochemical system is presented for in situ biochemical sensing. The sensing component of the system is a stretchable electrode array all‐printed with soft polymer and conductive silver nanowires. The electrodes show stable electrical properties within strain range of 0–50%, without serpentine designs. The electronic component of the system is a fully integrated flexible circuit board with near field communication module, which enables wireless energy harvesting and data transmission with smartphones. The system demonstrates good performance in real‐time on‐body sweat analysis for simultaneous quantitative detections of glucose, hydrogen, sodium, and potassium. This battery‐free and wireless epidermal electrochemical system provides a simplified, miniaturized, and flexible solution for a wide range of biochemical platforms, including wearable and implanted bioelectronics.