Recurrent Braiding of Thin McKibben Muscles to Overcome Their Limitation of Contraction

This study presents a novel idea of rebraiding thin McKibben muscles to overcome their limitation of contraction. The thin McKibben muscles, presented in the authors' previous work, have the flexibility that allows them to be braided. According to the experimental results of our previous research, the original single muscles have a contracting ratio of 28%, and the corresponding value for the muscles braided once is 37%. In this research, we achieved 41% contraction of thin McKibben muscles by braiding twice. The contraction ratio increases if the muscles are braided more. They will then overcome their limitation of contraction. In this report, several prototypes of muscles with different braiding times are designed, fabricated, modeled, and tested. As a result, the increase in the contraction ratio was confirmed from both a theoretical and an experimental point of view; the results were promising. We believe that recurrent-braided thin McKibben muscles will considerably help improve and develop various soft robotic applications in cases where a high contraction ratio is required.