1, characteristics and reasons of waterproof and self-cleaning of lotus leaves
Lotus effect refers to the self-cleaning phenomenon of lotus. In 1970s, Barttelot, a botanist at Bonn University, found that smooth leaves had dust on their surfaces, which had to be cleaned before they could be observed under a microscope, while the surfaces of waterproof leaves such as lotus leaves were always clean. They found that the special structure on the surface of lotus leaves has self-cleaning function. Lotus has been a symbol of purity since ancient times, so this self-cleaning function is also called "Lotus Effect".
Lotus leaf effect mainly means that the surface of lotus leaf is super-hydrophobic and self-cleaning. Because the surface of lotus leaves is hydrophobic and does not absorb water, the rainwater falling on the leaves will form water droplets under the action of surface tension. In other words, the contact angle between water and the leaves will be greater than 150 degrees, and the water droplets will roll off the leaves as long as the leaves are slightly inclined. Therefore, even after a downpour, the surface of lotus leaves can always remain dry; In addition, the rolling water drops will take away some dust and sludge particles by the way, achieving the effect of self-cleaning, which is also the reason why lotus flowers are always spotless.
Barttelot, they found under the microscope that there was a layer of fluff and some tiny waxy particles on the surface of the lotus leaf. The water on these nano-sized tiny particles will not spread in other directions on the surface of the lotus leaf, but form spheres, that is, we see rolling rain or dew on the lotus leaf, and these rolling water droplets will take away the dust on the surface of the leaf, thus cleaning the surface of the leaf.
The efficiency of lotus effect is extremely high. Scientists simulated the surface of lotus leaves and invented nano self-cleaning clothes and architectural coatings. Only a little water is needed to form water droplets, which can automatically clean clothes and building surfaces.
A bionic composite material has the characteristics of self-cleaning like a lotus leaf, so it is called lotus effect.
The fact that the blade surface cannot be attached by water droplets has been verified and widely known. But people often ignore that such a surface is also difficult to stain.
On a smooth surface, dirty particles will only move with the dripping of water droplets, and they will adhere to the rough surface produced by the rolling of water droplets and be washed down. This relationship was not noticed until recently and was confirmed by experiments.
Because this phenomenon is often seen on the large shield-shaped leaves of the lotus, which is regarded as a symbol of purity in Asian culture, people call it the "lotus effect".
If water drops roll on the lotus leaves, they will roll up all the dust particles and take them away from the leaves. This "lotus effect" principle is very effective, even on the "ravaged" lotus leaf, it is impossible to attach water droplets and dust particles.
The special surface structure and wax production function make the lotus leaf almost unaffected by other natural phenomena. It is very different from human's reaction to the influence of nature, such as the influence of chemicals in the environment and so on.
For the chemical substances belonging to surfactants that have to be widely used at present, plant preparations are widely used all over the world in order to maintain effective nutrients in plants. These activators not only destroy the perfect structure of waxy crystals, but also make the leaves easily wetted by water. And as a result, the dirty substances on plants will no longer be completely removed, but will be infected by microorganisms such as spores, fungi or bacteria that can infect plants in an unsatisfactory environment.
Lotus leaf effect describes a very effective biological model system. Because it is based on pure physical and chemical principles, it can be used to make artificial antifouling surfaces.
There are many fields and aspects that need this kind of application, such as the outer surface of cloth, roof, automatic painting machine and so on. If we can realize the self-cleaning function in these fields, it will obviously bring many benefits and save the cleaning cost. In industrial cooperation, efforts are being made to turn the lotus leaf effect into practical technical application. Although it will definitely take some time, this practical product will definitely come on the market sooner or later.