Passive, Electromagnetic‐Responsive Hydrogel Immunosensor for Exercise Intensity Monitoring Based on Sweat C‐Reactive Protein

ABSTRACT Although moderate exercise benefits health, excessive amounts of prolonged, high‐intensity exercise may damage tissues and cause inflammation‐related diseases. There is a growing interest in exercise‐related health monitoring and tracking; however, a handy, noninvasive, and accurate method for wearable detection of exercise‐induced inflammation still lacks. Here, this work reports a wireless and passive immunosensor for the noninvasive, low‐cost, and simple monitoring of C‐reactive protein (CRP) in sweat as an inflammatory marker to evaluate exercise‐induced inflammation. The sensor has a sandwich structure, in which the middle layer is an immuno‐sensitive hydrogel whose internal network structure cracks with the entry of CRP. A pair of coils converts the change of hydrogel into a shift of radio frequency (RF). The limit of detection (LoD) is as low as pg mL −1 , covering the concentration range of human sweat CRP. The sensor can be used in direct detection for sweat samples from subjects, demonstrating a correlation between exercise‐induced inflammation and exercise intensity. By tracking daily sweat CRP, the wearable passive immunosensor provides a methodology to quantify exercise intensity in terms of inflammation and has potential in customizing personal exercise protocols.