The lotus-effect is a natural phenomenon which could be observed on the surface of the lotus flower leaves and refers to the high water repellence they exhibit.
Small dirt particles are collected by the water droplets themselves thanks to a complex micro- and nanoscopic structure of the surface, thus reducing the adhesion.
At first sight lotus leaves seem as if they are completely smooth. However, they are covered with nanostructures, forming tiny air bags, on which the liquids flow down without penetrating the surface, thus leaving it completely clean all the time.
This turned out to be a surprise to the scientists working in this sphere, since until recently they have thought that only a smooth surface could be clean.
This natural phenomenon has inspired nanotechnologists to develop such a technique which using the same nanostructures forms hydrophobic coatings with a self-cleaning effect.