Conductive silk fibroin hydrogel with semi-interpenetrating network with high toughness and fast self-recovery for strain sensors.

Regenerated silk fibroin (RSF) hydrogels have been extensively studied in the fields of biomedicine and wearable devices in recent years due to their outstanding biocompatibility. However, the pure RSF hydrogels usually exhibited frangibility and low ductility, limiting their application in many aspects severely. Herein, we demonstrate a tough RSF/poly (N, N-dimethylallylamine) hydrogel with semi-interpenetrating network, which possesses good mechanical properties with high stretchability (ε = 900%), tensile strength (σ = 101.7 kPa), toughness (W = 516.7 kJ/m) and tearing fracture energy (T = 407.3 J/m). Besides, the gels show low residual strain in the cyclic tests and rapid self-recovery (80% toughness recovery within 5 min with the maximum strain of 400%). Moreover, the gels also show high ionic conductivity due to the incorporation of the NaCl and the hydrogel can act as an ideal candidate for strain sensor with high sensitivity (GF = 1.84), admirable linearity, and good durability (1000 cycles with the strain of 100%). When used as a wearable strain sensor for monitoring human movements, it also can detect small and large deformations with high sensitivity. It is expected that this work can provide a new strategy for the fabrication of smart RSF-based hydrogels and expand their application in multiple scenarios.