Conductive and Self‐Adhesive Polyelectrolyte Hydrogel Sensor for Flexible Wearable Devices and Reusable Physiological Electrode

Hydrogel-based flexible wearable devices and physiological electrodes have garnered increasing attention owing to their biocompatibility and comfort. However, accurate sensitivity for tiny deformation and low electrical conductivity are still limitations for ideal hydrogel sensors and electrodes. In this work, a multifunctional conductive polyelectrolyte hydrogel was prepared with cationic monomer 3- (methacryloylamino) propyl-trimethylammonium chloride, at the same time, polyphenolic compound tannic acid and glycerol were introduced to the hydrogel network to enhance the adhesion performance and environmental tolerance. The polyelectrolyte hydrogel showed low hysteresis (below 10%), good self-adhesion (∼50 kPa), excellent biocompatibility and antibacterial activity, satisfactory conductivity (8.5 mS m^-1), long-term stability (∼10 000 repeated cycles), wide strain sensing range (0.1%-100%), and accurate sensitivity even for human pulse monitoring. A flexible wearable device was designed for real-time monitoring of multiple movements and outdoor sports. In addition, a reusable self-adhesive electrode was designed based on the polyelectrolyte hydrogel for physiological signal monitoring, including electroencephalogram (EEG), electrocardiogram (ECG), and electromyogram (EMG). The electrode exhibited a superior signal-to-noise ratio, long-term stability, and sensitivity compared to traditional commercial electrodes. This study provides a promising material platform for long-term stable and accurate signal monitoring in flexible wearable electronics.