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ABSTRACT--In this paper we describe the experimental analysis of a novel ion-exchange polymer metal composite (IPMC) actuator under large externa~ voltage. The experimental analysis is supplemented with a coupled thermodynamic model, which includes mass transport across the thickness of the polymer actuator, chemical reactions at boundaries, and deformation as a function of the solvent (water) distribution. In this paper, the case of large electrode potentials (over 1.2 V) has been analyzed experimentally and theoretically. At these voltage levels, electrochemical reactions take place at both electrodes. These are used in the framework of overpotential theory to develop boundary conditions for the water transport in the bulk of polymer. The model is then simplified to a threecomponent 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 to be the dominant species responsible for the deformation of the IPMC actuators. Experiments conducted at different initial water contents are described and discussed in the context of the proposed deformation mechanism. Comparison of numerical simulations with experimental data shows good agreement.

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Ionic polymers are a promising material for the development of muscle-like actuators. These materials are capable of undergoing significant deformation when structured as metal-polymer-metal composite sheets. The mechanical characteristics of these sheets, such as flexibility, softness, and ability to undergo large deformation in direct contact with water, have led some to consider these as possible artificial muscles. This paper describes the numerical analysis of an electrochemical model of the deformation of muscle-like polymers. A general continuum model describing the transport and deformation processes of these actuators is briefly presented, along with a detailed description of the simulation scheme used to predict deformation, current, and mass transport. The predictions of the model are compared with experimental data, indicating a significant role of water transport in the large-scale deformation. The model is also used to draw a comparison between the performance of natural muscles and muscle-like polymer actuators.

A composite actuator based on a polymer electrolyte and metal electrodes is described. Electrode deposition is described qualitatively with corresponding experimental results. A general continuum model describing the transport and deformation of solid polymer electrolyte processes is developed. The formulation is based on global integral postulates for the conservation of mass, momentum, energy, charge, and the second law of thermodynamics. The global equations are then localized in the volume and on the material surfaces bounding the polymer. The model is simplified to a three component system of a fixed negatively charged polymeric matrix, diffusing hydroxonium ions, and free water within the polymer matrix. Contrary to the existing electrostatic models, the deformation is attributed to water induced swelling. The proposed internal pressure based model includes the stress relaxation phenomenon due to water redistribution governed by Darcy's law.