Nafion/polyimide based programmable moisture-driven actuators for functional structures and robots

Sustainable and environmentally friendly actuators powered by humidity, light and magnetic field are of great significance to facilitate application of microrobots. Among them, moisture-driven actuators have attracted a growing interest as a result of the widespread presence and ease of use of humidity. Nevertheless, the rapid acquisition and large-scale application of the moisture-driven actuators is still difficult since synthesis process of humidity-sensitive materials is time-consuming and complex. In this paper, we proposed a facile and rapid method to prepare double-layer moisture-driven actuators by integrating commercial humidity-sensitive Nafion ™ membrane and polyimide (PI) tape with good stability. Compared with other double-layer moisture-driven actuators, the so-obtained actuator has excellent performance in both the bending curvature (from −0.98 cm⁻¹ to 5.34 cm⁻¹) and the response speed (0.29 cm⁻¹/s). Through programmable structure design, a series of functional structures with complex deformation modes, i.e. torsion and bending, were realized. By imitating organisms like birds, vines, inchworms and ants, a series of soft robots have been developed based on the programmable structures to achieve behaviors including grasping, crawling and weight-bearing. The proposed programmable moisture-driven actuators have shed light on the fast development of environmental-friendly functional microrobots making use of ambient humidity.