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Home  > Raw materials & technologies  > Science today - coatings tomorrow  > Instead of easy-to-clean know about nothin...

Wednesday, 18 September 2019
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Raw materials & technologies, Science today - coatings tomorrow

Instead of easy-to-clean know about nothing-to-clean

Wednesday, 6 June 2012

What if there would be no hand necessary to make any surface clean of dust, dirt or other liquids? A step towards this future is made.

Left: Micrometer-scale structured polystyrene surfaces for use with micro-fluids. Right: Static wetting of this type of surface with water – simulation and experiment Source: Fraunhofer IWM
Left: Micrometer-scale structured polystyrene surfaces for use with micro-fluids. Right: Static wetting of this type of surface with water – simula...

Remember the lotus leave: A drop of water on it falls of by itself. No question of drying this leave with a paper or wiping it off. It is a self-cleaning surface and a good example of nature what needs to be copied to make it valueable for different other materials.

A new simulation program show how surfaces have to look

A software analyses what goes on within a given droplet – how the individual water molecules interact with each other, how a droplet is attracted by the surface and how it resists the air. Researchers at the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg have now developed a simulation software that provides the answers. "Our simulation shows how various liquids behave on different surfaces, no matter if these are flat, curved or structured,” explains Dr. Adham Hashibon, project manager at the IWM.

The program simulates the form the liquid droplets take on the surface, indicating whether the liquid distributes itself over the surface, or contracts to form droplets in order to minimize contact with the surface. The program is also able to calculate the flow behavior in terms of how liquids move across different surfaces, whereby the determinant factors at different scales of measurement are integrated, from atomic interactions to the impact of microscopic surface structure.

Microfluidity and surface characteristics are parameters

Researchers refer to a three-phase contact link between liquid, surface and air. "How liquid behaves on a surface is influenced by a great deal of parameters, including the surface characteristics of the material as well as its structure, but also by substances dissolved in the liquid. We have taken all this into account to different degrees of detail within the simulation so that we are able to clearly reproduce our experimental findings,” says Hashibon.
Improving microfluidic systems
The simulation will now be used to help optimise such microfluidic systems and to design surfaces so that as little liquid as possible gets left behind. "Our goal was to better understand and control the wetting behavior of liquids on structured surfaces,” says Hashibon. But that’s not all. This tool can also be used to implement a kind of traffic management system within the microfluidic system. When a channel splits into two, giving each fork a different surface structure makes it possible to separate the various components of the liquid.

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