Untethered Pneumatic Rubber Actuators for Soft Robots

Actuators that utilize the deformation of rubber by air pressure are called pneumatic rubber actuators. They are one of the most typical soft actuators due to their simple structure, large force and displacement, and structural softness, but pneumatic source, control valves, and pneumatic hoses are required for their driving, which is the biggest drawback of pneumatic rubber actuators. This is not a big problem when the actuators are applied to tethered system like endoscope, but it is a fatal drawback to be applied to untethered systems.<br/>Even in the case of electric actuators, they require a power supply, transistors, and electric wires. This is the same as pneumatic rubber actuators, but in the case of pneumatic actuators, each element is much larger and bulkier. In my talk, I will introduce two types of untethered pneumatic rubber actuators and their applications to soft robots in my laboratory.<br/><br/>One is a method using reversible gas/liquid phase change chemical reaction; electrolysis and synthesis of water. A proton exchange membrane PEM is used for the reaction which is controlled by electrical current. While applying current generates oxygen gas and hydrogen gas from water, increasing the volume and the pressure, shortening the electrodes or connecting them to an empty capacitor makes the gasses return to water. An important point is that this works as a fuel cell during the gas absorption process. This means that the chemical energy is recovered to electrical energy, resulting in efficient driving. We will introduce Basic experiments, applications to McKibben artificial muscles, and application to untethered robots will be shown.<br/><br/>The other is a pneumatic rubber actuator consisting of thin rubber film on which multiple DEAs (dielectric actuators) are formed. The actuator is initially filled with compressed air and activating each DEA sequentially causes travelling waves of rubber deformation. The point is that after initially applying the air pressure the actuator can be separated from the air source. Basic experiments and a demonstration in which an object is conveyed by a traveling waves.