Joint wrinkles in animals facilitate frequent bending and contribute to the duration of the joint. Inspired by the morphology and function of joint wrinkles, we developed a bionic hydration-induced polymeric actuator with constructed wrinkles at the selected area. Specifically, we adopt electrical writing to create defined single and double cross-linking regions on chitosan (CS) hydrogel. The covalent cross-linking network was constructed by electrical writing-induced covalent cross-linking between CS chains and epichlorohydrin. Subsequent treatment of sodium dodecyl sulfate allows electrostatic cross-linking at the unwritten area with the simultaneous formation of surface wrinkles. The resulting single and double cross-linking hydrogel demonstrates spontaneous deformation behaviors by the influx and efflux of H2O to the electrostatic cross-linking domain under different ion concentrations. Importantly, the wrinkle structure endows the hydrogel with extraordinary antifatigue bending performance. By regulating the surface morphology and spatial cross-linking, we can design novel biomimetic polysaccharide hydrogel actuators with fascinating functions.
Keywords: antifatigue; chitosan hydrogel; cross-linking; hydration-induced actuator; shape memory; surface wrinkle.