Vapor Lubrication for Reducing Water and Ice Adhesion on Poly(dimethylsiloxane) Brushes.

Fast removal of small water drops from surfaces is a challenging issue in heat transfer, water collection, or anti-icing. Poly(dimethylsiloxane) (PDMS) brushes show good prospects to reach this goal because of their low adhesion to liquids. To further reduce adhesion of water drops, here, the surface to the vapor of organic solvents such as toluene or n-hexane is exposed. In the presence of such vapors, water drops slide at lower tilt angle and move faster. This is mainly caused by the physisorption of vapor and swelling of the PDMS brushes, which serves as a lubricating layer. Enhanced by the toluene vapor lubrication, the limit departure volume of water drop on PDMS brushes decreases by one order of magnitude compared to that in air. As a result, the water harvesting efficiency in toluene vapor increases by 65%. Benefits of vapor lubrication are further demonstrated for de-icing: driven by gravity, frozen water drops slide down the vertical PDMS brush surface in the presence of vapor.