Graphene oxide and low-density polyethylene based highly sensitive biomimetic soft actuators powered by multiple clean energies of humidity and light

Abstract

Soft actuators based on smart materials can utilize external stimuli, especially clean energy sources such as light and humidity in nature, to achieve controllable actuation and perception, which has attracted much attention in the development of smart robots. However, most existing soft actuators based on light or humidity stimulation may suffer from several shortcomings, such as low response sensitivity, a single response mode, and an inability to achieve a multi-stimulus cooperative response. Hence, inspired by the biological structure of plants, we have fabricated soft double-layer actuators with ultrahigh sensitivity by casting a graphene oxide (GO) solution on a low-density polyethylene (LDPE) film. With just 40 mW cm⁻² of NIR light, the actuator can quickly change from the curled state to the flat state, achieving an angle change of 500°, which is less than the natural light intensity (80 mW cm⁻²). Moreover, the actuator also showed a rapid response (∼2.6 s) and large deformation (500°) under humidity stimulation. As an application concept demonstration, the actuator can be assembled into a crawling robot that mimics inchworms crawling on a leaf, an adaptive soft gripper that grabs different shapes of cargo, and a rotating robot driving a boat forward. The soft actuator will have great potential in smart bionics, energy conversion, and other emerging fields in the future.