High-response tri-layer electrochemical actuators based on conducting polymer films

Sandwich structured tri-layer films of polypyrrole/gold/polypyrrole have been electrochemically synthesized by successive oxidation of pyrrole in aqueous solutions and sputtering deposition of a thin gold layer, respectively. One of the polypyrrole layers was doped by a relatively large anion, dodecylbenzene sulfonate (PPy(DBS)) and the other one was doped by a smaller anion, benzenesulfonate (PPy(BS)). The tri-layer film could be deformed quickly by electrochemical reduction and oxidation of polypyrrole layers. The thin gold layer provided a highly conductive support for actuation. The tri-layered film could move from a position of 0° (vertical) to a position of +90° (oxidation) or −90° (reduction) at potentials higher than 0.7 V or lower than −0.7 V (vs. saturated calomel electrode (SCE)), respectively. The movement rate of the tri-layer film was ∼260°/s at potentials of ±1.2 V vs. SCE, which was five times that of a PPy(DBS)/PPy(BS) bi-layer film. Furthermore, the tri-layer film could be driven at potentials as low as ±0.2 V vs. SCE. The bending motion rate of the tri-layer film increased quadratically with the increase of driving potential, while the motion rate of the bi-layer film, PPy(DBS)/PPy(BS), increased linearly with an increase of driving potential.