Rapid water-responsive shape memory films for smart resistive bending sensors.

• We first develop a simple film with good wet strength, rapid water response and water-induced shape memory. • The mechanical robustness of MCP films is improved in low pH solutions, and the films show a rapid pH stimulus response. • MCP films exhibit excellent water-induced shape memory and a rapid pH stimulus response. • After rapid bend-release repetitions (0°–90°–0°) for 500 cycles, the resistive bending sensor deliver stable electrical signals. [Display omitted] Development of multi-functional water-sensitive shape memory material is crucial for applications in smart textiles, artificial intelligence, and biomedical areas. However, it remains a great challenge to achieve good biocompatibility, rapid water response, and robust mechanical strength in one single material. In this respect, we report a green approach to produce a series of multi-functional water-sensitive memory films (named MCP films) from sisal cellulose microcrystals (MSF-g-COOH), peach gum polysaccharide (PGP), citric acid (CA), and graphene nanosheets (GN). After crosslinking with CA, MCP films exhibit excellent water-induced shape memory and rapid pH stimulus response. More importantly, MCP films can effectively amplify different external motion stimuli by converting them into independent electrical signals to achieve accurate and continuous perception of bending. A high-performance resistive bending sensor was further fabricated from the MCP films to mimic natural human skin. The resistive bending sensor exhibited excellent water-responsive shape memory, self-adhesion, and bending sensitivity, which can be used in electronic skin, human-machine interactions, intelligent wearable devices, personalized health monitoring and other applications. Our work successfully demonstrates the application of the water-sensitive shape memory films in electronic skin and health-monitoring components, and fills the gap between material design and high-performance devices. [ABSTRACT FROM AUTHOR]