An Electrochemical Actuator Fabricated by Transfer-printing of a Carbon Electrode onto a Cupric-ion-containing Poly(acrylic acid) Gel Surface

Highly functional polymer-gel materials that include highly conductive gels, moving gels, and stimulation-responsive gels are important in a number of applications, including actuators, microrobots, and artificial muscle; hence, the development of new gels with superior properties is an important objective. Herein, we report the fabrication of a flexible electrochemical actuator by the direct transfer of a carbon electrode, formed by screen-printing on a silicone sheet, onto the surface of a poly(acrylic acid) gel containing cupric ions, which was prepared by immersing the poly(acrylic acid) gel in a 0.1 mM copper sulfate solution. Due to the oxidation of copper and the reduction of cupric ions, when potentials of 0.6 V and −0.7 V are alternately applied to the poly(acrylic acid)-cupric-ion gel actuator, it repeatedly expands and contracts along with concomitant copper-ion redox transformations when immersed in 0.1 M aqueous sodium perchlorate. This actuator demonstrated a 0.29% change in expansion ratio, which is 2.3-times larger than that of a previously reported electrochemical actuator (0.13%) formed with a sputtered gold electrode on a conventional polymer substrate.