G. Di Pasqualea, A. Pollicinoa, M. Bottinoa, C. Bonomob
aDipartimento di Metodologie Fisiche e Chimiche per l’Ingegneria, V.le A.Doria 6, 95125 Catania (Italy),( http://www.dmfci.unict.it; email@example.com)
bDipartimento di Ingegneria Elettrica Elettronica e dei Sistemi, V.le A. Doria 6. 95125 Catania (Italy)
Electro-Active Polymers (EAP) are soft polymers which develop mechanical strain if subjected to electrical stimuli or, on the contrary, which produce voltages if mechanically deformed. Their discovery has led to take into account their possible use as sensor-actuator for both bio-mimetic applications and traditional robotics. The EAP main attractions are the capability to emulate biological muscles and, for this reason, they have been named “artificial muscles”. Ionic polymer-metal composites (IPMCs) belong to wet EAP. They generally are fabricated by chemical plating of conductive electrode layers such as gold, copper or platinum on both surfaces of a perfluorinated ionic polymer which can absorb large amounts of polar solvents, i.e. water. The bending mechanism of an IPMC actuator is electro-osmosis: when an input voltage is applied to the electrode layers, the cations, combined with water molecules in the ionic polymer, move toward the cathode and the actuator bends to the anode side due to the volume change. However, water contained in the polymer membrane gradually evaporates through porous electrode layers during actuation. The water leakage reduces the performance of the IPMC such as displacement, force and lifetime. A key engineering problem in achieving high force density IPMC is reducing or eliminating the water leakage out of the surface electrode so that water transport within the IPMC can be more effectively utilized for actuation. This can be achieved by introducing dispersing agents during the chemical reduction process: these additives should enhance dispersal of platinum particles within the ionic polymer and thus reduce coagulation. As a results, a better metallic particle penetration in the polymer with a smaller average particle size and more uniform distribution could be obtained. This uniform distribution make it more difficult for water to pass through. Thus, the water leakage out of the surface electrode could be significantly reduced. In this study, to optimize experimental conditions for the preparation of nano-sized metal particles, the influence of different kinds of dispersing agent (polyvinylpirrolydone, at different molecular weight, and sodium dodecyle sulphate), at various concentration, have been studied. Surface morphology and performance changes of the IPMC were discussed.