Fully flexible liquid-to-gas phase change actuators with integrated liquid metal heaters

Abstract In recent years, soft robots have been attracting interest because of their potential for new application fields. Among soft actuators for soft robots, liquid-to-gas phase change actuators have the advantage of structural simplicity. However, the actuators require an external heater to vaporize a low boiling point liquid inside the actuator. The heater typically consists of a solid electrode that often reduces the durability and flexibility of the heater. In this study, we propose a small liquid-to-gas phase change actuator with an integrated liquid metal heater. A low boiling point liquid and liquid metal heater were encapsulated in a nylon-polyethylene bladder using wire molding. The proposed soft actuator has high flexibility and durability against bending because of the material used. We experimentally characterized actuators of different sizes with respect to the generated force, displacement, and time response. We also confirmed that the soft actuator could work even after bending 1000 times.