A Light-Activated Polymer Composite Enables On-Demand Photocontrolled Motion: Transportation at the Liquid/Air Interface

Abstract

Swimmers at liquid/air interfaces have drawn enormous attention because of their potential applications. Described herein is one novel light-driven swimmer based on a bimorph composite structure of a photoresponsive liquid-crystalline polymer network and a commercially available polyimide (Kapton). The motion of the swimmer can be controlled by photoirradiation. The bilayer-structured film shows quickly photoinduced bending towards the Kapton side upon exposure to UV light, and recovers immediately after removal of light. When placed on a liquid surface, the swimmer propels itself continually though rhythmic beating the liquid like a dolphin moving forward with its tail fin. Besides, light-powered rotation of the swimmer is successfully achieved by simply changing the length-width ratio and the irradiation site, mimicking the function of a dolphin's pectoral fin. Combining the forward movement and rotation motion together, on-demand directional control of the photo-driven swimmer can be readily obtained at room temperature, showing promise for miniaturized units for transportation.

Keywords: azo compounds; interfaces; materials science; molecular devices; photochemistry.