Facile preparation of superhydrophobic PDMS with patternable and controllable water adhesion characteristics

Control of water adhesion is important for superhydrophobic surfaces in various applications. In this work, we present a facile approach to prepare superhydrophobic polydimethylsiloxane (PDMS) with patternable and controllable water adhesion capabilities. Surface grafting of N-isopropylacrylamide was primarily exploited to regulate the PDMS template morphologies, either by tuning the ultraviolet irradiation duration or adopting repeated grafting process. The surface topologies of as-prepared PDMS templates can be flexibly constructed with roughness degrees ranging widely from 1.5 to 738.7 nm. Followed with covering of carbonyl iron particles (CIP) on the template surface, the duplicated PDMS substrate can thus recur the surface topology incorporated with CIP onto the upper surface, leading to the feasibility to regulate diverse water adhesion capabilities. Owing to the synergistic effect by the surface roughness and CIP incorporation, the water adhesion capabilities of the PDMS substrates can be flexibly tuned ranging from droplet pinning to excellent water repellency. The presented strategies were further developed to create PDMS substrates with patterned water adhesion for controllable micro-droplet transportation or rapidly programmable droplet localizations. We believe that the environmentally friendly method can offer as a convenient yet cost-effective tool for future microfluidic devices, biochemical analysis, etc.