Multiphase media superwettability regulated by coexisting prewetting phase

Abstract

Understanding the wetting behaviors of a given superwetting surface in multiphase media is important for elaborately tailoring superwettability. Here the surface chemistry of two types of superhydrophobic surfaces was programmed to reveal crucial effect of a coexisting prewetting phase rather than the prewetting process on their wetting states in water and oil–water separation application. After prewetting with ethanol to remove the air layer, underwater contact angles of superhydrophobic surfaces for oil droplet and bubble gradually decreased from over 150° along with the reduced surface energy. When the superhydrophobic surfaces were directly immersed in water or prewetted with oil, a stable air layer or infused oil as the prewetting phase enabled oil droplet and bubble to rapidly spread out. Moreover, air-prewetting superhydrophobic/underwater superoleophobic fabric can selectively adsorb oils from water, whereas it showed an excellent antifouling property without the air layer. For the separation of oil-in-water emulsions using superhydrophobic/underwater superoleophilic sponge, the stable air layer obstructed emulsions into three-dimensional porous structures. After removing the air layer, emulsion separation can be efficiently realized. This discovery provides a feasible approach for the regulation and development of unusual superwettability in multiphase media.