Beads of water form on the surface of a leaf. This phenomena was discovered on the Lotus plant and patented by the botanist Wilhelm Barthlott. The natural self-cleaning properties of the leaf are produced by a microscopically rough and super-hydrophobic surface. The surface tension of the water is greater than the adhesion strength to the surface of the leaf, resulting in the formation of droplets that roll off and pick up dirt along the way. Biomimetic nanotechnologies, including coatings, paints and surface treatments, have been developed to mimic the lotus effect on clothes, products and buildings façades.