A highly resilient and large-strain wearable hydrogel sensor based on acrylamide/gelatin/Zr4+ and its application in human motion monitoring and information transmission

The application potential of flexible electronic technologies across diverse interdisciplinary domains has become increasingly evident. Owing to their unique combination of flexibility, biocompatibility, and skin-mimetic mechanical properties, hydrogels have emerged as a central material for wearable flexible sensors. Nevertheless, conventional hydrogel-based sensors often suffer from inadequate mechanical performance under high stress and large strain conditions, along with limited toughness. Gelatin, a natural protein, possesses a molecular structure abundant in hydroxyl and amino functional groups, enabling the formation of a highly extensible, hydrogen-bonded flexible network and exhibiting excellent biocompatibility. In this study, a thermally induced free-radical polymerization approach was employed to construct a covalently cross-linked rigid framework using polyacrylamide (PAM), while incorporating gelatin to establish a hydrogen-bond-reinforced flexible network. Concurrently, Zr 4+ were introduced to coordinate with anionic functional groups on both gelatin and PAM chains, resulting in the fabrication of a polyacrylamide/gelatin/zirconium ion composite hydrogel sensor (PMG x Z y ). The PMG x Z y hydrogel sensor demonstrates exceptional toughness, rapid response dynamics, high sensitivity, and a broad sensing range. It achieves a strain of up to 924 % under a stress of 0.26 MPa, with a fracture energy of 1.12 MJ m −3 . The sensor not only enables real-time monitoring of large-amplitude human motions but also facilitates sound recognition, handwritten pattern detection, and information transmission via integration with Morse code encoding. This work effectively overcomes the mechanical limitations of traditional hydrogel sensors, offering a promising new material platform for wearable sensing applications in fields such as outdoor sports monitoring and rehabilitation training.