Fabrication of super-hydrophobic film with dual-size roughness by silica sphere assembly

Two simple approaches were developed for the fabrication of super-hydrophobic film with dual-size roughness by taking advantage of assembling silica micro- and nanospheres. Electrostatic adsorbing technique and template-directed self-assembly were used here. The dual-size surface, which mimics the surface topology of lotus leaves, comprises both the micro-scale and nano-scale roughness. After the roughened surface was chemically modified with a layer of fluoroalkylsilane, super-hydrophobicity with a water contact angle higher than 160° and sliding angle as low as 0.5° can be achieved. The simplicity and cheapness of this procedure may make widespread applications of this super-hydrophobic film possible.