Electrically driven PEDOT/PSS actuators

The film made of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT/PSS) was prepared by casting and electrical conductivity, tensile properties, electromechanical response, and moisture sorption isotherm of the PEDOT/PSS film were investigated. A linear expansion of the PEDOT/PSS film occurred with increasing ambient humidity, where the strain of the film in a RH range from 20 to 90%RH was 3.3%. Upon application of an electric field, the film underwent significant contraction in ambient air. The degree of contraction increased as the applied voltage became higher and the value attained 2% at 35 V, which was nearly twice as that of polypyrrole films. The principle lay in the desorption of water vapor due to local Joule heating, where the electric field controlled an equilibrium of water vapor sorption. The moisture sorption isotherm of the PEDOT/PSS film indicated that the interaction between water and PEDOT/PSS was superior to that between water molecules, in which isosteric heat of sorption decreased with an increase in the sorption degree and the value reached to the heat of water condensation.