Au/Pt Double-Layer Electrodes and Expanding Internal Chamber for Improving Air-Hose-Free Thin McKibben Muscles

Abstract

Air-hose-free thin McKibben muscles with a soft polymer electrolyte fuel cell (PEFC) tube can realize electrically controlled actuation with a soft body. However, they experience the following problems: low response speed, fast deterioration of PEFC tube electrodes, and the requirement for high driving voltage. In this paper, we propose two breakthrough technologies that improve the performance of air-hose-free McKibben muscles. One is an Au/Pt double-layer electrode, and the other is an expanding internal chamber. We use these technologies to successfully increase the expansion rate and decrease the excessive pressure rise inside a PEFC tube. The resistance of the PEFC tube with the Au/Pt double-layer electrodes increases only slightly after it is bent eight times. Theoretical calculations show that the installation of the expanding internal chamber can increase the pressure for contracting the muscle by up to 300%. The improved air-hose-free thin McKibben muscle achieves a maximum contraction ratio of 22% and a contraction time of 35 s. The contraction ratio is approximately four times larger than that obtained in previous research. The newly proposed air-hose-free thin McKibben muscle is applied to an antagonistic drive robot arm to demonstrate its applicability in robotic systems. The prototype of the antagonistic drive robot arm is successfully operated with a rotation speed of 2.4 deg/s and a maximum displacement angle of 83 deg.