Imagine a bridge or pipeline where every drop of water simply fell off—never puddling, even in the smallest nooks and crannies.
German researchers are working on that future now, with a new simulation program that can show a critical step in the corrosion process: how water behaves on a surface.
While “self-cleaning” coatings are hardly new, the technology is still improving. Coated surfaces do not yet keep themselves free of water and other liquids.
But they could, the researchers say, if coating scientists knew more about how water behaves from the instant it hits the coated surface.
© Fraunhofer IWM
|A simulation image (left) shows the behavior of a drop of water on a surface—an understanding that could lead to more effective protective coatings. The simulation findings later became the basis of an experiment (right).|
Researchers at the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg thus set out to answer a basic question: What characterizes surfaces that do the best job of cleaning themselves?
The institute’s new simulation software is providing important answers, the team says.
“Our goal was to better understand and control the wetting behavior of liquids on structured surfaces,” explains Dr. Adham Hashibon, project manager. “Our simulation shows how various liquids behave on different surfaces, no matter if these are flat, curved or structured.”
Form and Flow
The program simulates the form that liquid droplets take on the surface, indicating whether the liquid distributes itself over the surface, or contracts to form droplets so as 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.
The software even analyzes 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 refer to a three-phase contact link between liquid, surface and air.)
A coating that makes water fall off by itself could have many applications as well, the team says.
Corrosion coatings would put up a better fight against rust if water did not collect on top. Eyeglasses and windshields would not need to be wiped. In the medical world, such coatings could improve microfluidic systems.
How Liquids Behave
“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,” says Hashibon.
The researchers say the simulation will allow them to reproduce their experimental findings.