Table of contents:
2023 Author : Hannah Pearcy | [email protected] . Last modified: 2023-05-24 11:12
Houses that are clean after the rain: "Flower-pure" facades owe their cleaning to the lotus effect, copied from nature. Susanne Wierse The ability to repel dirt made the lotus a symbol of purity, fidelity, creative power and enlightenment in large parts of Asia. So the symbol is found in both Hinduism and Buddhism. The enlightened ones - Buddhas - are depicted on an open lotus flower or a lotus throne. The lotus effect is the low wettability of a surface that can be observed in the lotus plant, but also in other plants such as the lady's mantle or on white cabbage leaves. The water rolls off in drops and takes dirt particles from the surface. This observation sparked Wilhelm Barthlott's curiosity in the 1970s. The young botanist was fascinated by the newly emerging scanning electron microscopy, which provided plastic images down to the nanometer range. He uses the new technology to research plant surfaces. In doing so, he tracked down the special surface of the lotus. Due to their high surface tension, water drops tend to make their surface as small as possible and therefore try to achieve a spherical shape. When in contact with another surface, the adhesive forces normally act on the surface and the water drops are distributed. Water is repelled on hydrophobic - water-repellent - surfaces. The droplets that form are narrow and high, so that they have as little contact with the surface as possible. Normally the angle of a drop from the wetted surface is about 90 degrees on a hydrophobic surface. In contrast, the contact angle on the lotus leaf is 150 degrees. The water forms almost spherical drops that roll like balls. Why is that? The knowledge This is where the special surface structure of the lotus leaf comes into play. Contrary to what you might think, the reason is not a particularly smooth surface, but a highly complex, three-dimensional structure. It reduces the contact area between the surface and the particles lying on it as well as water drops and thus reduces the attractive forces so much that there is a self-cleaning effect. In addition, a wax formed by the lotus plant rests on bumps approximately 10 to 20 micrometers high and 10 to 15 micrometers apart. The water no longer has the possibility of getting into the gaps between the leaf surface, which means that the contact area between the water and the surface is drastically reduced. The attraction between the leaf surface and water drops is so low that the water can easily roll off. Overlying dirt particles are only held on small tips and can therefore easily be taken away by a rolling water drop. Even hydrophobic (water-repellent) dirt particles are washed off the surface of the plant because their adherence to the surface of the plant is less than that of the water drop. Wilhelm Barthlott discovered the super hydrophobic surface. The Implementation Coating an object so that it becomes super-hydrophobic was not easy. It was not until the 1990s that the principle was successfully translated into technology. Wilhelm Barthlott created a spoon in-house production, from the nubbed silicone surface honey dripped off without residue. This product finally convinced some large chemical companies of the technical feasibility of the idea. Since the end of the 1990s, physicists and materials scientists in particular have studied the phenomenon intensively, and there is now a very extensive literature and dozens of dependent patents. The transfer The facade paint Lotusan is the first example of the successful transfer of the Lotus effect into practice:Homeowners have been benefiting from dry and beautiful exterior walls for many years. The product has proven itself in practice on many million square meters of facade space worldwide.
practice plus
With Lotusan, real all-round products are available when it comes to facade protection and design: When used correctly, surfaces coated with Lotusan colors stay clean longer than other facade coatings. The facade color is classic and - for extremely stressed facades - with film preservatives. With the StoLotusan K / MP facade plaster, Sto has succeeded in transferring the lotus effect to a facade plaster. The result is a finishing coat for the outside with excellent properties in processing, building physics and facade protection. Further information: www.sto.de www.lotusan.de
