Photoreversible Superhydrophobic Surfaces with Switchable Sticky-Rolling State of Water Droplets

A photoresponsive fluorinated azobenzene homopolymer is synthesized via TERP. UV irradiation of the surface based on a fluorinated azobenzene homopolymer with micro/nanostructures induces a tunable/switchable water droplet mobility. Water droplets can easily roll off the pristine surface at a small tilt angle (≈14°). The apparent water CA changes from 150 to 135° after UV illumination of the surface. Thus, water drops stick on the surface when the substrate is turned vertically or even upside down, indicating a very high adhesion force. Interestingly, the water droplet rolls off again under visible-light irradiation. The as-prepared surface may be useful for applications requiring switchable mobility of water droplets.