Ultrathin film actuators fabricated by layer-by-layer molecular self-assembly

Polymer/metal cluster nanocomposite thin films as new types of electroactive polymer (EAP) material have been synthesized by the layer-by-layer (LBL) electrostatic self-assembly process. A self-assembled 11-bilayer poly-S-119/Pt nanocluster film, with a thickness of approximately 30 nm and a Pt content of 0.49 at.%, exhibited an actuation response similar to that of conventional ionic polymer-metal composite films for low applied voltage in air, but nonlinear bending behaviour in response to a slightly higher applied voltage. The film has a uniform nanostructure with the Pt nanoclusters dispersed within the multiple molecular layers, as confirmed by atomic force microscopy. The self-assembled electroactive films may have different actuation mechanisms from those of traditional piezoelectric materials, and from other EAP materials, due to the quite different LBL laminated structure. Further studies concerning the principles governing the novel processing of the films and applications are underway.