Ruling out delamination in bismuth-enhanced polyimide electrochemical actuator with tunable active/passive layer thickness

Abstract

Ionic electroactive polymer (iEAP) actuators have attracted wide attention due to their capability of producing desired deformation under low voltages by ion diffusion. However, these actuators are always subjected to a slow response and fatal delamination at the bonding interface during deformation. Here, we report a novel polyimide/gold/bismuth (PI/Au/Bi) actuator driven by the electrochemical redox of PI with tunable active/passive layer thickness to generate large and tunable strain, where metallic Bi is indispensable to promote the actuating behavior by enhancing the reversible redox of PI. Much faster charge transportation and better conductivity of the PI/Au/Bi film were observed after coating with Bi. The actuator demonstrated large and tunable strain under a long service life owing to the fact that PI acted as both the active layer and passive layer, which effectively ruled out the delamination issue. This work not only develops bismuth-enhanced ionic actuators, but finds a new use for low-dielectric-constant polymers rather than conductive polymers as actuator materials.