Hydrogen Bonding-Driven Poly(vinyl alcohol)/Cellulose Nanofibril Hydrogels with AgNPs for Sensitive Motion Monitoring

The development of conductive hydrogels for flexible strain sensors is frequently limited by the trade-off between mechanical strength and the uniform dispersion of conductive fillers. This study reports the fabrication of a high-performance, biodegradable poly(vinyl alcohol) (PVA)/cellulose nanofibril (CNF) hydrogel via a cyclic freeze–thaw process, coupled with the in situ reduction of silver nanoparticles (AgNPs). Beyond their role as a mechanical reinforcing phase, TEMPO-oxidized CNFs establish a robust hydrogen-bonded dual network with the PVA matrix and simultaneously serve as active nucleation templates, promoting the preferentially uniform distribution of AgNPs along the CNF scaffold and substantially reducing interparticle agglomeration tendencies. The resulting PVA-CNF-Ag hydrogel demonstrates outstanding mechanical properties, including a tensile strength of 158.6 kPa and superior compressive fatigue resistance. Electromechanically, the optimized hydrogel achieves a high gauge factor of 3.36, maintaining stable and repeatable signal outputs over 300 stretch–release cycles. Furthermore, the sustained release of silver ions provides excellent broad-spectrum antibacterial efficacy against Escherichia coli and Staphylococcus aureus . Epidermal sensing demonstrations confirm the sensor’s capacity to precisely monitor multiscale human motions, ranging from large-joint movements to subtle physiological signals such as phonation and swallowing. This work establishes a sustainable, robust, and durable material platform for next-generation wearable electronics.