Micro Elastic Pouch Motors: Elastically Deformable and Miniaturized Soft Actuators Using Liquid-to-Gas Phase Change

In the present study, we propose a largely deformable and miniaturized soft actuator that is made by an elastic rubber bladder (called a pouch) with a low-boiling-point liquid. When the temperature of the low-boiling-point liquid reaches 34 $^{\circ }$C, the liquid inside the pouch evaporates, and the whole structure inflates. Thanks to the proposed fabrication method, we can make a miniaturized pouch of approximately 5 mm in diameter with a thin rubber membrane, and the pouch can inflate to a volume of 86 times or more compared to its initial volume and can generate approximately 20 N at maximum. We calculated the deformation model and developed the fabrication process through investigation of the thickness and the inflation volume of the pouch with respect to the process parameters. We then experimentally characterized the actuator with respect to the generated force, time response, and repeatability of the inflation. We believe that micro elastic pouch motors will contribute to soft robotic systems as a new component as a result of having unique characteristics, such as millimeter size and large deformability.