Development of Pneumatic Artificial Rubber Muscle Using Segmented Shape-Memory Polymer Sheets

We have developed a pneumatic artificial rubber muscle using two shape-memory polymer (SMP) sheets. We attached the SMP sheets to a linear pneumatic artificial rubber muscle. Utilizing the large difference in the elastic modulus below and above the glass transition temperature, the shape fixity and shape recovery of SMPs, the bending direction and the initial shape can be changed. In this study, in order to increase the bending motion range, we developed a segmented SMP sheet with embedded electrical heating wires, and evaluated its mechanical properties using bending and tensile tests. Moreover, we attached such sheets to an artificial muscle and evaluated the bending motion. Bending tests showed that segmenting the SMP sheets greatly reduced their bending stiffness. In tensile tests at temperatures below the glass transition temperature, it was found that the artificial muscle with the attached sheet withstood high elongating loads without failure. Attachment of such segmented SMP sheets to an artificial muscle resulted in an increased bending angle. Through isotonic and isometric tests, we showed that the prototype actuator could bend in two directions.