The lotus effect is not a biological, but a physical-chemical phenomenon and can be described with physical-chemical parameters:
The angle of water contact is the decisive factor
That is the angle between the surface of the substrate and the surface of the water droplet on it. It is a measure for the wettability of the surface with water. This angle can be changed by applying nano sealants to the surface.
Nano-structured surfaces become hydrophobic
That means water repellent. Such hard to wet surfaces have a large contact angle. Materials structured in the nano range have contact angles of up to 170 degrees.
On a nano-structured surface, the actual contact area is only two to three percent of the surface covered by a water droplet. The drop lies as if on a bed of nails made of crayons and touches only their tips. This decreases the attraction between the water and the substrate, the water droplets become round.
Surfaces with such a low wettability cannot get wet. Not even for cleaning. But dirt has to be dissolved by water. The beading effect looks good in many commercials – but has practically no significance for cleaning.
If a surface is to be cleaned with water, it has to be wettable. A surface that repels water entirely can thus no longer be cleaned with water.The surface starts smearing as soon as it comes in contact with water. This effect can be seen in many nano products – but of course the commercials never mention it.
The ideal contact angle
On normal smooth surfaces the water droplets cannot roll off, only glide. Then they slip over the dirt without removing it.
The ideal contact angle must thus be between the normal and the hydrophobic contact angle in order to remove loose dirt when the water rolls off while still allowing stubborn dirt to be cleaned using water.
The secret of nanotol
In the development of nanotol
a great effort was made to leave the contact angle just large enough to allow water to roll off, but also allow the surface to be moistened for cleaning. nanotol is not only water repellant, but fat, dirt, and oil repellant also. more
On a surface treated with nanotol
the water draws together, slides off at an angle and takes the dirt with it. Round droplets are not formed using nanotol. At the same time, the surface is smoothed so that dirt, lime, and fat cannot become trapped and can be easily removed with clear water.