Size Effects of Surface Roughness to Superhydrophobicity

Water droplets placed on a superhydrophobic surface act like soft balls that can easily deform, roll and bounce, leading to various novel behaviors such as self-cleaning and anti-icing. Thousands of plant and animal species have been observed to have superhydrophobic surfaces and all these surfaces seem to have roughness sizes in the micro-submicron range. The classical models don not predict this kind of specified size phenomenon. Here we review some recent findings, which show that scaling down the surface roughness into the micro-submicron range is a unique and elegant strategy to not only achieve superhydrophobicity, but also increase its stability against environmental disturbances. We further demonstrate that these findings can guide fabrication of stable and extreme liquid-repellant surfaces.