As the samples in nature are examined biomimetrically, the lotus plants' leaves are superhydrophobic, i.e. drops of water roll off free of residue, taking any impurities with them. Systematically arranged, water-repellent, nano-size wax crystals form three-dimensional structures, similar to small nipples, which are no greater than a few nanometers or micrometers in size. 

 

When combined with the waxes' water-repellent chemical properties, these structures make the lotus leaf extremely non-wettable, a state called super-hydrophobic, and they give it its self-cleaning properties. The dirt particles only sit on the tip of the wax crystals and as a result only a very small surface area comes into contact with the plant's surface. If water falls onto a leaf surface like this, the interplay of the surface tension and the low attraction force between the surfaces and the water produce a spherical water drop which only sits on the tips of the wax structures. If the leaf tips in the slightest, the water drop immediately rolls off, taking the dirt particles with it. As the gravitational pull between the dirt and the leaf's surface is very slight, i.e. it is smaller than that between the water and the dirt, even lipophilic impurities, such as soot for example, can be drop off away.