UV-driven self-replenishing slippery surfaces with programmable droplet-guiding pathways

Smart surfaces with special wettability properties have attracted remarkable attention due to the potential for extensive applications in liquid manipulation techniques. However, the challenges in lubricant-wastage and the programmable droplet sliding pathway remain. Here, a silicon oil-infused porous slippery surface was fabricated with UV-responsive controllable wettability (UVRS), and then, the UVRS was integrated with a non-UV-responsive slippery surface (NUVRS) to form composite UV-responsive surfaces (CUVRSs). Due to the conformational transformation of the azobenzene groups under UV light irradiation, the lubricant lost from the surface could be self-replenished, eventually rebuilding a new lubricant layer to re-form the slippery surface. Besides, the color of the exposed surface changed simultaneously, thus providing a new way to monitor the wettability changes and droplet sliding route. By adjusting the design of the "cutting patterns" on NUVRSs and the pattern of the UV masks, the droplet-guiding channels could be programmed orderly. In addition, these programmable droplet pathways could not only be used for point-to-point liquid transportation but also for constructing tailored microfluidic- and micro-reactors. These findings provide a novel way to rebuild smart slippery surfaces and design programmable droplet sliding pathways, thus advancing the application of intelligent slippery surfaces in liquid manipulation, microfluidics and micro-reactor settings.