The Lotus effect refers to self cleaning properties that are a result of ultrahydrophobicity as exhibited by the leaves of lotus flower. As water droplets fall on the surface of leaves then it rolls away carrying dirt that has settled along it's way.
The surface of the plant has a contact angle of 180 degree and any substance with a contact angle of above 150 degree is considered super hydrophobic . Beneath the waxy leaf of the Lotus are small bumps called papillae which leads to easy roll off water along with the dirt .
Material scientists are trying their best to mimic such surface so that they can find an alternative to Teflon, since Organo flourine compounds have been shown to lead to environmental persistence and toxicity .
This is a promising area of research for anyone interested in material science.