Electrically Driven Polypyrrole Film Actuator Working in Air

The polypyrrole (PPy) films containing tetrafluoroborate ions were electrochemically synthesized and electrically driven motion of the film was investigated. The application of dc voltage brought about reversible contraction of the film in air, where the degree of contraction increased with increasing both applied voltage and ambient humidity. The contraction of the film was associated with desorption of water vapor due to the Joule heating, which was different from electrochemical doping and dedoping. The degree of contraction attained 1.2% under 2 V, where the initial speeds of contraction and expansion of the film were 4.4 and 1.8% min-1, respectively. Under loading conditions, the power density increased with increasing load and the value attained 0.78 W kg-' (6 V.W) under the load of 60 g (4 MPa). The energy efficiency, defined as the ratio of work done by the PPy film to the electric energy, was calculated as 6.6 x 10-3%.