Zr⁴⁺-Coordinated Highly Stretchable and Conductive Silk Fibroin/PPy Hydrogel for Flexible Wearable Sensing

Conductive hydrogels are promising materials for fabricating flexible wearable strain sensors. However, their practical application remains limited by several challenges, including poor mechanical strength, unstable sensitivity, restricted stretchability, and poor structural durability. In this study, a zirconium-reinforced conductive hydrogel (PSPZr) with a dual chemical-physical cross-linked network was designed and developed. In the structural framework, polypyrrole-decorated silk fibroin (SF/PPy) functioned as a conductive reinforcing component, acrylamide and sulfobetaine methacrylate constituted the flexible polymer basis, and zirconium ions (Zr⁴⁺) acted as ionic cross-linkers to construct a dual cross-linked structure and improve mechanical stability. Due to the synergistic contributions of hydrogen bonding, ionic coordination interactions, and SF/PPy, the optimized PSPZr hydrogel exhibited a tensile strength of 166 kPa and a maximum strain 559%. Additionally, it achieved improved elasticity and reliable shape recovery. Furthermore, the optimized PSPZr hydrogel exhibited a broad working range, sensitivity with a gauge factor of 2.8, rapid response, recovery kinetics, and exceptional cycling stability over 1000 stretching-releasing cycles as wearable strain sensors. This performance enabled real-time and accurate monitoring of diverse human motions. Therefore, this study presents a feasible and versatile strategy for developing mechanically robust and electrically stable conductive hydrogel, providing a new pattern for advanced applications in wearable sensors.