Reliable and large curvature actuation from gradient-structured graphene oxide

By utilizing the density gradient and upward convection flow induced by solvent evaporation, the exfoliated graphene oxide (GO) nanosheets in aqueous solution were assembled into a hierarchically structured GO paper, by which a temperature-triggered actuator was then fabricated. When stimulated by temperature, the GO paper could bend to a large curvature. At 100 °C, the curvature could reach 0.36 mm^-1 within 60 s. The mechanical properties of as-prepared actuators have also been studied. The actuator exhibited a stress of 1.4 MPa when exposed to a temperature of 80 °C and showed almost identical actuating stresses in cyclic measurements. The actuation mechanism is directly related to the loss/acquisition of the interlamellar water during temperature change. Reliable and large curvature actuation could be attributed to the unique gradient structure of the pure GO papers.