Ionic polymer–metal composite actuators exhibiting self-oscillation

In this paper, we present a fascinating new feature of ionic polymer–metal composite (IPMC), “self-oscillation”. In the presence of small organic molecules (SOMs) in an aqueous medium, the self-oscillatory and periodic deformation of IPMCs was evident. The oscillations are caused by the potential periodicity in the Pt anode where the activation-overpotential is altered by complex surface reactions under an applied dc current. Such a self-oscillatory behavior of IPMC was highly conceivable and repeatable when it was properly prepared. The importance of surface reactions can be acknowledged when the electrochemical reactions among potential intermediates, such as PtOH, PtO, and PtCO are believed to exist. The oscillatory potential was obtained by properly alternating the presence and the absence of CO molecules on the anode at a constant current.