Bioinspired untethered soft robot with pumpless phase change soft actuators by bidirectional thermoelectrics

Soft pneumatic actuators play an important role in the technological advancement of soft robotics, but they face intrinsic limitations due to the presence of complex and bulky air compressors and tubes, that make it difficult to design completely soft robotic systems. In this study, we develop a first demonstration of the soft thermo-pneumatic actuating module that operates based on the thermally controlled gas-liquid phase transition with the soft thermoelectric device. The bi-directional thermal managing ability (heating and cooling) of the thermoelectric device is capable of controlling the inflation and deflation of the pneumatic chamber with the aid of the thermally conductive silicone rubber that enhances the heat transfer. For the first time to the authors’ best knowledge, we demonstrate the active cooling of the thermoelectric device that accelerates the deflation rate by the active cooling functionality that significantly reduces the whole operating time. Additionally, to validate its practical usage in soft robotics, the soft actuating module shows different motions, such as bending and rectilinear stretching, based on the assembly design that is employed to develop the soft gripper and the entirely untethered soft earthworm robot without a complicated and bulky compressor system.