Double-side coated electrochemical actuator based on changes in volume of poly(acrylic acid) gel

An actuator consisting of two poly(acrylic acid) gel films which sandwich a polyimide film coated with Au layers on both sides was developed. The actuator was driven by changes in the volume of the gel induced by redox reaction of p-hydroquinone (QH2)/p-benzoquinone (BQ). The oxidation of QH2 results in decrease in pH, which gives rise to collapse of the gel, whereas the reduction of BQ does the opposite phenomena. The Au film electrodes on both sides of the actuator were used as two electrodes setup. Thus, when the oxidation takes place at one electrode, the reduction does on the other electrode at the opposite side at the same time. In a solution of 5 mM QH2 and 5 mM BQ containing 1 × 10−4 M NaClO4 the actuator bent to left (anode) side at 1.3 V, and bent to right side after the reversal of the polarity. The actuator showed repeated stretching/bending at least 200 cycles. Further, it was able to actuate after 6 times of repeated drying/wetting of the gel.