Hofmeister Effect-Regulated Lightweight and High-Strength PVA/CMC Hydrogel for Durable Sensing

Traditional conductive hydrogels suffer from intrinsic mechanical brittleness (typically <1 MPa) and insufficient fatigue resistance, making them prone to structural failure during dynamic wearable applications and long-term use, which inevitably leads to signal drift. Herein, poly(vinyl alcohol) (PVA) was used as the matrix; sodium carboxymethyl cellulose (CMC) constructed a flexible double-network framework; tannic acid (TA) enabled energy dissipation via dynamic hydrogen bonding; and sodium sulfate (Na2SO4) triggered Hofmeister effect-driven crystallization, thereby yielding an ultratough and fatigue-resistant conductive hydrogel. Benefiting from the hierarchical structure, the hydrogel achieved integrated mechanical-electrical performance. After the optimized 16 h Na2SO4 treatment, it exhibited an ultralow density of 0.962 g/cm3, a tensile strength of 10.05 MPa (40 × conventional PVA), a toughness of 18.92 MJ/m3, and an ionic conductivity of 3.97 S/m (34.5 × conventional PVA). The fabricated sensor showed excellent fatigue-resistant sensing performance, maintaining >91% signal retention after 5000 stretching cycles at 100% strain, with a rapid response time of 167 ± 9 ms, enabling high-fidelity monitoring of joint motions and physiological pulses. When integrated with machine learning, the system enabled Morse-code communication and achieved a gesture-recognition accuracy exceeding 93%. This study provides a simple and feasible strategy for constructing ultratough, fatigue-resistant conductive hydrogels for next-generation durable bioelectronic devices.