Development of curved type pneumatic artificial rubber muscle using shape-memory polymer

A conventional curved type pneumatic rubber artificial muscle is composed of an internal bladder covered with a bellows sleeve extending axially. By inhibiting the extension of one side with a fiber reinforcement, bending motion occurs when air is supplied to the bladder. In this study, we developed a new actuator by replacing the fiber reinforcement with a shape-memory polymer (SMP). The SMP can be deformed above its glass transition temperature (T_g) and maintains a rigid shape after it is cooled below T_g. When next heated above T_g, it returns to its initial shape. When only part of our actuator is warmed above T_g, only that portion of the SMP is soft and can actuate. Therefore, the direction of the motion can be controlled by heating. Moreover, our actuator can be deformed by an external force above T_g and fixed when its initial shape is below T_g.