Time evolution of current and displacement of ion-exchange polymer/metal composite actuators

Abstract

This dissertation describes the development of a coupled model for the analysis of a novel polymer/metal composite (IPMC) actuator under large external voltage. A general continuum model describing the transport and deformation processes of solid polymer electrolyte is proposed. The formulation is based on global integral postulates for the mass conservation, charge conservation, momentum equilibrium, the first law of thermodynamics, and the second law of thermodynamics. The global equations are localized in the volume and on the material surfaces bounding the polymer. The model is simplified to a three-component system comprised of a fixed negatively charged polymeric matrix, protons, and free water molecules within the polymer matrix. Among these species, water molecules are considered as the dominant specie responsible for the deformation of the IPMC actuators. In this work, the electrochemical process occurring at both electrodes is analyzed as boundary conditions during the deformation of actuator in the regime of large voltage (over 1.2 V). These are used in the framework of overpotential theory to develop boundary conditions for the water transport in the bulk of polymer. The proposed coupled model successfully captures the stress relaxation phenomenon due to water redistribution governed by diffusion. The fabrication process are described, and experiments including the role of initial water content on the electro-mechanical response of the actuator are also discussed. Comparison of simulations and experimental data showed good agreement.