Thermoplastic polyurethane/graphene oxide composite membrane actuatable by infrared irradiation or humidity change

A single stimulus of the intelligent actuator cannot cope with the complex environment, and the intelligent actuator with the synergistic effect of multiple stimuli will be better applied to the complex environment. Herein, the flexible composite membrane consisting of a graphene oxide (GO) layer and a thermoplastic polyurethane (TPU) layer has been fabricated through evaporation membrane formation and distributed spin-coating technique. The TPU/GO membrane demonstrates remarkable actuation response to humidity and infrared (IR) light stimuli. The maximum response bending Angle of 60 degrees was reached within 1.06 s under 150 W IR light, and the maximum reverse bending Angle of 108 degrees was reached within 3.8 s under 90 % RH humidity. The actuator also delivers good flexion recovery performance after undergoing 200 cycles of cyclic response tests. At the same time, due to the difference in water absorption or desorption between GO and TPU layers, the GO and TPU layers in the juxtaposition structure show different response rates to infrared light and humidity stimuli, and the actuator can utilize alternate conversion of contraction and expansion. Moreover, the difference in thermal expansion between the GO layer and the TPU layer also prompts the actuator to respond under infrared light. Under the co -stimulation of infrared light and humidity, the controllable and programmable "forward -stagnationreverse" cooperative driving response behavior is completed. Moreover, owing to the flexibility and maneuverability of the parallel GO/TPU membrane, it is best used in complex environments, which have a vast range of potential applications in biometrics and smart soft robots.