Polypyrrole-metal coil composite actuators as artificial muscle fibres

A polypyrrole (PPy) deposited electrochemically on W micro-coil with the diameter of 0.25 nun from methyl benzoate solution of TBABF(4) showed 11.6% apparent strain induced electrochemically in aqueous NaBF4 solution. This strain was slightly smaller than that (12.1%) of a free-standing PPy film prepared similarly on W electrode. However, taking the configuration of PPy-W coil (gap:wire diameter = 1: 1) into account, the effective strain of PPy at the gap of coil wires should be 23.2%. The enhanced contact area between W coil and PPy reduced voltage drop of the PPy, resulting in exhibiting the large strain. Electrochemically generated displacement and force can be easily tailored by adjusting the length and the number Of PPY-coil composite, respectively. The tailor-made actuator should be applicable to a variety of mechanisms, particularly to 'push' devices such as a plunger. (C) 2004 Elsevier B.V. All rights reserved.