A proposal of a light-weight walking assist wear using PVC gel artificial muscles

We have developed a contraction and expansion-type artificial muscle by using the plasticized polyvinyl chloride (PVC) gel and mesh electrodes. The PVC gel artificial muscle exhibits a fast response in air, large deformation, variable stiffness, high output force and low power consumption under an electrical field, so it has a great potential to use as a new type of artificial muscles. In a previous study, we designed variable stiffness spats for walking assistance by incorporating the variable stiffness PVC gel artificial muscles with the generally used spats. The spats can assist walking by the generation force of the variation of stiffness with the on and off switching of an electric field. It was found that both the integrated electromyogram (IEMG) and maximal voluntary contraction (%MVC) of the rectus femoris muscle decreased during the walking when wearing the variable stiffness gel spats which showed that it was possible to use the PVC gel artificial muscles for walking assistance. However, the variable stiffness spats has small generation force and lower robustness to external forces. In this study, we propose a novel approach to make a high-performance light-weight walking assist wear using the PVC gel artificial muscles. We use the contraction-expansion output force for motion assist to get a bigger generation force. An expansion type structure unit is introduced to make the assist wear more robust to external forces. Insole force sensors are used to detect the gait changes during walking. The proposed walking assist wear has the characteristics of a simple structure, light weight, easy to put on and take off and with a high flexibility. In this paper, the framework involving the proposed walking assist wear is described in detail.