Nacre-inspired moisture-responsive graphene actuators with robustness and self-healing properties

Moisture-responsive actuators based on graphene oxide (GO) have attracted intensive research interests in recent years. However, current GO actuators suffer from the low mechanical strength. Inspired by the robustness of nacre structure, moisture-responsive actuators with high mechanical strength and self-healing properties were successfully developed based on the GO and cellulose fiber (CF) hybrids. The hybrid paper demonstrated significantly improved tensile strength, ~20 times higher than that of pure GO paper, and self-healing property. A broken paper can be well cured under moisture treatment, and the mechanical properties of the self-healed hybrid paper can still maintain similar tensile strength with the pristine one. After controllable ultraviolet light photoreduction treatment, the hybrids paper with a photoreduction gradient along the normal direction was prepared, which can act as moisture-responsive actuators. The max bending curvature can reach ~1.48 cm-1 under relative high humidity (RH=97%). As a proof-of-concept, a butterfly-like actuator that can deform itself under moisture actuation was demonstrated. Our approach may pave a new way for designing robust and self-healable graphene actuators.