Ionomeric Polymer-Metal Composites (IPMC) are attractive type of electroactive polymer actuation materials because of their characteristics of large electrically induced bending, mechanical flexibility, low excitation voltage, low density, and ease of fabrication. The diffusion of ions between the electrodes causes the material to bend. The unique features of the IPMC materials and their need for special operating environment require new approaches to measuring their characteristics. A macro model that relates the electric input and mechanical output is required for the material characterization and application. This paper addresses the macro models for the electric inputs and electromechanical actuation of IPMC. A distributed RC line model is developed to describe the varying capacitance of the electric input behavior and a four-parameter model to express the relaxation phenomena. The power capacities of the IPMCs are estimated according to the established models and the measured results. Results for several types of IPMCs, which present different behaviors, are presented.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.