The state of understanding of ionic polymer metal composite architecture: a review

Ionic polymer metal composites (IPMCs) are electroactive polymers (EAPs) that are used as soft actuators and sensors. Various mechanical or chemical manufacturing techniques, used for manufacturing IPMC, impart a layered structure that plays a significant role in transduction. These layers comprise of the polymer that constitutes the bulk of the IPMC (polymer layer), the metal used for electroding (electrode layer) and the composite consisting of dispersed metal particles in the polymer matrix (intermediate layer). While ionic pendent chains in the polymer layer are responsible for the charge transport in IPMCs, the metal particles in the intermediate and electrode layers act as conductive pathways for current transmission. At the same time the layered structure imparts a capacitive nature to the IPMC, which positively affects the ionic transduction in the IPMC. The role of each layer and the coupling between them is important for improving IPMC properties and, hence, transduction. The aim of this article is to review the research conducted on IPMC fabrication and layered architecture and study their role in IPMC transduction.