Super-water-repellent surface

S. Shibuichi, T. Yamamoto, T. Onda and K. Tsujii, Super water-repellent surfaces resulting from fractal structure, J. Colloid Interface Sci. 208,287-294 (1998). 

Super water repellent coating is demonstrated at a facility in Palo Alto, California. Drops of water literally bounce off the surface of the material, which has a coating built from nanostructures. (AP Photo)... 

T. Onda, S. Shibuichi, N. Satoh, and K. Tsujii, "Super water-repellent fractal surfaces," Langmuir, vol. 12, pp. 2125-2127,1996. 

Shibuichi and co-workers prepared super water- and oil-repellent aluminum oxide surfaces by anodic oxidation [19, 21]. Two-aluminum plates were used as the working and the counter electrodes, respectively. After anodic oxidation of aluminum in 0.5 M H2SO4 solution at a constant current density of 10 mA/cm for 3 h, a fractal aluminum oxide was formed on the working electrode. After hydrophobization with fluorinated monoalkylphosphate or IH, IH, 2H, 2H-perfluorodecyltrichlorosilane, the WCA on the surface was measured to be larger than 160°. 

Canham LT, Cullis AG, Pickering C, Dosser OD, Cox TI, Lyneh TP (1994) Lumineseent anodized silicon aerocrystal networks prepared by supercritical drying. Nature 368 133-135 Cao L, Price TP, Weiss M, Gao D (2008) Super water- and oil-repellent surfaces on intrinsically hydrophilic and oleophillic porous silicon films. Langmuir 24(5) 1640-1643 Chao Y (2011) Optical properties of nanostructured silicon. Compr NanoSci Technol 1 543-570 Chuang SF, Collins SD, Smith RL (1989) Porous silicon microstructure as studied by transmission electron microscopy. Appl Phys Lett 55 1540-1543 Costa J, Roura P, Morante JR, Bertran E (1998) Blackbody emission under laser excitation of silicon nanopowder produced by plasma-enhanced chemieal-vapour deposition. J Appl Phys 83(12) 7879-7885... 

Shibuichi, S., Yamamoto, T., Onda, T., and Tsujii, K. 1998. Super Water- and Oil-Repellent Surfaces Resulting from Fractal Structure. J. Colloid Inteiface Sci. 208 287. 

L. Cao, T. R Price, M. Weiss and D. Gao, Super water- and oil-repellent surfaces on intrinsically hydrophilic and oleophihc porous sflicon films, Langmuir, 24, 1640-1643 (2008). 

Water and soil repellency has been one of the major targets for fiber and textile scientists and manufacturers for centuries. Combinations of new materials for fiber production with a variety of surface treatments have been developed to reach the condition of limited wettability. Nevertheless, additional efforts has been needed to create fiber and textile materials with ideal repelling properties. Nature has already developed an elegant approach that combines chemistry and physics to create super-repellent surfaces. Lotus leaves are unusually water repellent and keep themselves spotless, since countless miniature protrusions, coated with a water-repellent hydrophobic substance, cover their surface. Water cannot spread out on the leaves and it rolls around as droplets, removing grime and soil as it moves. 

The opposite of super-hydrophobicity, the Lotus Effect, is super-oleophobicity, the Pitcher Plant Effect. A natural example of super-oleophobicity involves the Nepenthes Pitcher Plant, which has microtextured surfaces in which an aqueous liquid fills the spaces within the texture and forms a continuous overlying film to cause insects to slip into the plant s digestive juices. Here, the plant s super-oleophobic surface essentially repels the oils on the insects feet. This is termed the Pitcher Plant Effect. Microporous, microfibre coatings have been developed to mimic this effect and be highly repellent to oils while remaining permeable to water. 

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