In 1975 discovered the botanists Barthlott and Neinhuis from the University of Bonn the self cleansing capability of the Lotus flower. The scientists observed that Lotus flowers get rid of mud and dirt while unfolding their leaves in the morning. So they examined the leave surface structure of the Lotus with a scanning electron microscope discovering a not as expected smooth but a very rough structure (10-9 nano and 10-6 micro).
This rough structure is responsible for the super hydrophobic ability of the leaves. The leave’s surface has a double layer structure first it is covered by little pimples (papillae) whereupon a layer of hydrophobic wax lies. The Wax prevents raindrops from getting into the pimples interspaces resulting in only 2% – 3% of the drops surface being in contact with the leaf. Additional is the contact angle at which a liquid or vapor meets a solid surface responsible for the water-repellent. The smaller the contact angle (<90o), the flatter the droplets and the wetter the surface. The larger the contact angle (>90o) the less the area of contact between the liquid or vapor and the solid interface, leading to a closer to dry surface. The Lotus pimples create a contact angle of over 150°. These effects reduces the strength of adhesion and vests the lotus flower with a super hydrophobic surface.
In many Asian religions is the Lotus flower due to the cleanness revered as a symbol of purity.
As the Lotus effect has been introduced into Bionics it has found its way to commercial use. Today we can find the Lotus effect in the textile industry producing hydrophobic cloth. Other fields of use include glass, plastics, painted surfaces, metals and ceramics and equipped with a hydrophobic ability these products outpace competitors.