Technical note - Lotus effect: Superhydrophobicity

The relationships among contact angles, surface tensions, and surface roughness are reviewed. The various numerical formulae related to contact angles were used to predict the surface tension and wetting behavior of polymer surfaces. The apparent contact angle of a droplet deposited on a textured surface is presented, and the characteristics required for a superhydrophobic surface are described. This study also presents the effect of the sliding angles of liquid droplets on smooth and rough surfaces. The contact angle hysteresis was found to be very important in understanding the drop motion on a surface. Contact angle hystereses increased on a Wenzel-type surface, while a Cassie-Baxter type surface reduced the hystereses for the same surface roughness and surface tensions.