Soft actuator with large volumetric change using vapor-liquid phase transition

Soft robotics has become an attractive research topic with the recent development of soft actuators. Herein, we propose a deformable soft actuator with large volumetric changes. The proposed elastomer contains liquid droplets; their transition from the liquid phase to the vapor phase can be controlled by heat. We chose silicone and urethane rubbers as the matrix materials; droplets of water and fluorine were dispersed homogeneously in the rubber matrix as micelles or solutes. After curing the rubber, bubbles appeared owing to microwave heating. We succeeded in generating a fine bubble structure using the proposed method, and we could reduce the leakage of the droplet material using urethane as the matrix material. Finally, we attempted to fabricate a small actuator to work in the channels. The proposed method can be useful for miniaturized soft robots.