Lotus Effect

Lotus leaf (Nelumbo nucifera) has become the epitome of natural superhydrophobic surfaces and has long been considered as a sacred symbol of purity for thousand years in oriental culture due to its impressive self-cleaning feature, where leaves remain unsmudged even being immersed into muddy water. Water contact angle on lotus leaf is reported above 160° with few degrees of roll-off angle. Therefore, lotus effect is sometimes a synonym for superhydrophobicity or self-cleaning nowadays. Although the effect has long been noticed for several generations, a systematically detailed investigation was not carried out until 1997 where more than 200 water-repellent plants were studied via scanning electron microscopy (Neinhuis and Barthlott 1997). The study reveals the secret of lotus leaf, which, not surprisingly, attributes to its combination of surface roughness and chemical substances. Hydrophobicity and self-cleaning of lotus leaf are believed as a mechanism to resist harmful...