Fabrication of superhydrophobic surfaces with double-scale roughness

A surface with micro- and nano-scale ZnO (zinc oxide) structure was fabricated by alkaline hydrothermal method. The CA (contact angle) on this double-roughness surface was low (down to similar to 0 degrees), but after spin-coating Teflon, the CA was increased to similar to 168 degrees. By observing with SEM, a rose like ZnO crystal surface structure was found, which was responsible for both superhydrophilicity and superhydrophobicity. The prepared surface also showed high chemical stability even after immersing the sample in water for 15 days. The method is simply controllable, cost-effective, and has a wide range of potential applications such as self-cleaning superhydrophobic coating on large areas of different substrates. (C) 2010 Elsevier B.V. All rights reserved.