The effect of surface-electrode resistance on the performance of ionic polymer-metal composite (IPMC) artificial muscles

TLDR

The study discusses how the IPMC’s equivalent circuit and electrophoretic cation transport influence its performance. The authors aim to reduce surface‑electrode resistance by electrochemically depositing a thin silver or copper layer on the platinum electrode. They fabricate IPMCs from a perfluorinated ion‑exchange membrane with platinum composite, optimize process parameters, deposit the metal layer, and test actuation under low voltage. Results show that the dense platinum layer increases surface resistance, but the added silver/copper layer lowers it, leading to higher actuation capability.

Abstract

Reported in this study are the effects of the surface-electrode resistance on the performance of ionic polymer-metal composite (IPMC) artificial muscles. The IPMC artificial muscles manufactured in this study is composed of a perfluorinated ion-exchange membrane, platinum composited by using a chemical processing technique that employs a platinum salt and appropriate reducing agents. Furthermore, the IPMC artificial muscles were optimized for producing improved forces by changing multiple process parameters including the time-dependent concentrations of the salt and reducing agents. However, the analytical results confirmed that the platinum electrode is successfully deposited on the surface of the material where platinum particles stay in a dense form that appears to introduce a significant level of surface-electrode resistance. In order to address this problem, a thin layer of silver (or copper) was electrochemically deposited on top of the platinum electrode to reduce the surface-electrode resistance. Actuation tests were performed for such IPMC artificial muscles under a low voltage. The test results show that the lower surface-electrode resistance generates higher actuation capability in the IPMC artificial muscles. This observation is briefly discussed based on the role that the equivalent circuit for the IPMC plays and a possible electrophoretic cation-transport phenomenon under the influence of an electric field.