Experimental Study of Ionic Polymer-Metal Composites in Various Cation Forms: Actuation Behavior

Ionic Polymer-Metal Composites ( IPMC's) are attractive materials, due to their capabilities of exhibiting large-motion sensing and soft actuation in a small electric field, mimicking biological characteristics and sensing situations. In this paper, the effects of counter-ions on the performance of IPMC's in actuation are discussed. Samples of hydrated IPMC's were prepared in a standard size of 0.25 χ 1 inch strip containing various monovalent and divalent metal cations, including Na, L i \ K \ H, Ca, Mg, Ba, and two organic cations, tetrabuthylammonium (TBA) and tetramethylammonium (TMA). Given a sinusoidal wave input of 1.2 volts and Ά Hz, the I PMC having Li as a cation shows the best performance in terms of force generation. Such results strongly indicate that ionic redistribution in an imposed electric field takes place, causing hydrated cations electrophoretically to move toward the cathode, producing a water movement. From this, it can be concluded that as the hydration increases, the generative force by the IPMC's increases. Also, the effect of large organic cations such as TBA and TMA, relative to the other cations listed above, is investigated. It has been observed that such IPMC's have slower response and produce smaller force in the same sample relative to Li. A simple phenomenological model for forces and fluxes will also be presented. K e y w o r d s : ionic polymer-metal composite (IPMC), artificial muscles, actuators, and sensors.