Low-Voltage-Driven Large-Amplitude Soft Actuators Based on Phase Transition

Soft actuators producing large motion in a short time are mostly based on stretchable polymers actuated by pneumatic pressure; they consist of bulky components, including a motor, pump/compressor, tubes, and valves. In this study, we develop a fast-responding large-amplitude soft actuator, based on a liquid-gas phase transition, which produces a compact system. The required pressure is generated solely by the electrically induced phase transition of a fluid in a cavity, mimicking the thigmonastic movements found in plants. We discuss the critical design variables to improve the performance and propose a new design for the electrodes, which are the most critical components. Our bending actuator produces large motion in <7 s, using a low-voltage source (<50 V) that allows a much faster response than the soft actuators based on phase transition currently available.