Zn-PAA-C hydrogel for integrated energy storage and self-diagnostic health monitoring in wearable biomedical devices

Wearable biomedical devices require materials that simultaneously integrate energy storage and sensing, function under extreme conditions, and enable battery self-diagnosis. To address this, we developed a novel ZnCl₂-loaded poly(acrylic acid)-based composite hydrogel (Zn-PAA-C) serving as both a flexible Zn-ion battery electrolyte and a high-performance strain sensor. Engineered with poly(acrylic acid) N-hydroxysuccinimide ester (PAA-NHS), gelatin, and ethylene glycol, Zn-PAA-C exhibits exceptional ionic conductivity, mechanical resilience, and freeze-resistance (down to -80 °C). As a strain sensor, it achieves a broad sensing range (0–180 % strain), reliable operation (1–7 Hz), and rapid response (57 ms). As a battery electrolyte, it uniquely incorporates self-diagnostic capability, enabling real-time monitoring of battery expansion and dendrite formation for enhanced safety and longevity, and supports stable operation over 12,000 charge-discharge cycles. Zn-PAA-C thus transcends traditional gel electrolyte limitations, establishing a new standard for multifunctional materials in wearable biomedical devices capable of robust, continuous health monitoring under extreme conditions.