Understanding the complementary roles of surface energy and roughness on natural nonwetting surfaces has led to the development of a number of biomimetic superhydrophobic surfaces, which exhibit apparent contact angles with water greater than 150 degrees and low contact angle hysteresis. However, superoleophobic surfaces-those that display contact angles greater than 150 degrees with organic liquids having appreciably lower surface tensions than that of water-are extremely rare. Calculations suggest that creating such a surface would require a surface energy lower than that of any known material. We show how a third factor, re-entrant surface curvature, in conjunction with chemical composition and roughened texture, can be used to design surfaces that display extreme resistance to wetting from a number of liquids with low surface tension, including alkanes such as decane and octane.

Superhydrophobicity was first observed in nature on a lotus leaf and some other plants when their leaves would not get wet. The main reason for that phenomenon was the unique surface structure of the lotus leaf and also the presence of a low surface energy material on the surface of the leaf. In order to achieve superhydrophobic surface or coating, the surface must possess hierarchical micro and nano roughness and low surface energy at the same time. Hierarchical micro and nano scale roughness will trap air on the surface that will cause an increase in the water contact angle and low surface energy will decrease the tendency of water to bond with the surface. So almost all the methods to achieve superhydrophobicity consist of two requirements of a hierarchical surface roughness as well as presence of a low surface energy material. These surfaces have many practical applications, from industrial to biomedical applications, including water/oil separation, self-cleaning, drag reduction, antifogging, anti-bacteria, anti-fouling, anti-icing, corrosion resistance, as well as many applications in industries such as marine, oil, and gas, aerospace, biomedicine etc. Hence, superhydrophobic surfaces, which can be achieved by surface modifications and/or surface coatings, have become very interesting in the last decade. The important issues and challenges in the field of superhydrophobic surfaces is stability and robustness of the surfaces.