Multi-layer graphene oxide coated shape memory polyurethane for adjustable smart switches

Multi-layer graphene oxide (MLGO) coated shape memory polyurethane (MLGO@SMPU) with different layers was fabricated by multiple dipping for adjustable shape memory switching devices. The MLGO, which stacked together in parallel, evenly covered the surface of the SMPU. Stress strain testing indicated that the coating of GO improved the mechanical strength of these MLGO@SMPU composites in the stretching stage below the strain of approximately 6%. Adhesive force testing suggested that the first GO layer could adhere well to the SMPU surface, but the interaction force between GO layers was weak. The angle recovery ratio and time, bending recovery force, and angle fixity ratio of these MLGO@SMPU composites were evaluated using homemade evaluation apparatus. Results indicated that with the increase of GO layers from one to five layers, the MLGO@ SMPU gave an angle recovery ratio reduced to 83.2%, recovery time decreased to 7.6 s, bending recovery force increased to 18.3 mN, and angle fixity ratio decreased to 83.3%. This novel and straightforward approach of dipping graphene oxide onto shape memory substrates for adjustable recovery ratio, time and force has the potential to be applied to smart switching devices including sensors and actuators.