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Lotus effect
The cause:
The Lotus-effect refers to the extremely small wettability and high self cleaning of biological surfaces, among others the Lotus plant. On the bloom and the sheets even extremely responsible colored powder is rinsed away by water, even water based adhesives are not able to stick to the surface. Other plants, as for example Reed and Bananas, show this effect too.
After the botanic-professor Wilhelm Barthlott of the University of Bonn stated that some plants were frequently dirty in the Herbarium, but other kinds remained always clean during many years, he examined this phenomenon more exactly and described its physicochemical bases as well as C. Neinhuis into the 1990er years.
The reason lies in the special surface texture. It shows microscopically small cell collections, which are scattered with still smaller crystals again. This double structure causes an impressing physical effect - water drops which fall on the sheet form themselves ,due to their surface tension, to a ball, then roll down from the sheet and carry away the contamination.
Opposite water contact angles of up to 160° are reached by the surface texture of the plants (they are super-hydrophobic). That means that only about 2 to 3% of the drop surface get in contact with the surface of the plant, this means the surfaces possesses an extremely small wettability. The adhesion between sheet surface and water drop is so small that the water can flow away easily. Dirt particles resting on the surface also possess only a small contact area – are rinsed away easily by the water flowing down. The central meaning of the surface tension of aqueous solutions to minimize the contact area makes understandable that the Lotus-effect in this form cannot occur with strongly moistening solvents.
Biological meaning:
The biological meaning of this effect for the plant lies in the protection from a settlement by micro organisms, pathogens or germs, for example mushroom pores, or the vegetation with algae. This is valid in similar way for animals as butterflies, spirit levels and other insects whose legs are not long enough to reach out over their whole body to clean themselves.
Application:
Meanwhile it succeeded to copy the surface textures artificially. Nano-products are e.g. self-cleaning roofing tiles and self-cleaning fronts. From the range of the nano-technology products there are meanwhile coatings which are super-hydrophobic. These surfaces are water-rejecting but not self-cleaning, they are only easy to clean.
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