Roughness-induced superhydrophobicity: a way to design non-adhesive surfaces

Non-adhesive and water-repellent surfaces are required for many tribological applications. Roughness-induced superhydrophobicity has been suggested as a way to reduce adhesion and stiction. In this paper, the theory of roughness-induced superhydrophobicity is presented. Wetting is studied as a multiscale process involving the macroscale (water droplet size), microscale (surface texture size), and nanoscale (molecular size). We study fundamental physical mechanisms of wetting, including the transition between various wetting regimes, contact angle and contact angle hysteresis. The effect of surface roughness upon wetting and capillary adhesion force is discussed. Practical recommendations for the design of superhydrophobic surfaces are formulated.