Searching for Clues about Maxwell Stress in the Back-Relaxation of Ionic Polymer-Metal Composites

The phenomenon of back-relaxation in ionic polymer-metal composites (IPMCs) has attracted the interest of the scienti fi c community for two decades, yet a conclusive explanation of why and when it occurs is presently lacking. Recent studies have suggested that the interplay between osmotic pressure and Maxwell stress could be the key mechanism underlying back-relaxation, but experimental proof is missing to substantiate this hypothesis. Here, we seek to bring forward new evidence from the technical literature in favor of this explanation by analyzing existing experiments on contactless actuation of ionomer strips in an electrolyte solution. We demonstrate that Maxwell stress dominates osmotic pressure in the contactless actuation of ionomers, thereby supporting the claim that Maxwell stress could help understand back-relaxation in IPMCs.