High-strength cellulose nanofiber/graphene oxide films with brick-mortar structure as rapid humidity/light dual-responsive actuators

Cellulose nanofibers have attracted significant attention in the burgeoning field of humidity actuators. However, traditional cellulose nanofiber actuators were hydrophilic, which exhibited low water resistance and poor stability in practical applications. To address these issues, herein, we report a facile vacuum-assisted filtration strategy for fabricating rapid humidity/light dual-responsive actuators composed of 2D hydrophilic graphene oxide (GO) and 1D hydrophobic cellulose nanofibers (HCNF). Benefiting from the unique self-assembled “brick-mortar” lamellar structure and strong hydrogen bonding interactions between HCNF and GO, the resultant HCNF/GO films exhibited good mechanical performances in both dry and wet states, whose tensile strengths were 257.5 MPa and 144.8 MPa, respectively. By combining the water absorption and barrier effects of GO with the water desorption of HCNFs, the bending angles of HCNF/GO actuators achieved 180.0° (hydration process) and 262.3° (dehydration process) within 1.7 s and 24 s, respectively. These actuators with remarkable mechanical properties and rapid humidity/light dual-responsive performance could be used in various soft robotics, such as swallow wings, bandages, mechanical arms, and smart curtains. Our HCNF/GO actuators could convert natural humidity fluctuations and solar irradiation into mechanical energy, which has great potential in low-carbon, energy-efficient applications in the field of soft robotics.