A team of engineers from the Northwestern University has identified ways to keep a surface dry for a longer period of time when submerged in water. This finding could help save billions of dollars in a variety of industries. The research team was led by theoretical mechanical engineer Neelesh A. Patankar. The Indian-origin scientist help identify the ideal surface 'roughness' needed in the texture to keep it dry under water for a longer period of time.
Patankar said, "The trick is to use rough surfaces of the right chemistry and size to promote vapor formation, which we can use to our advantage." The researchers found that the valleys in the surface roughness typically need to be less than one micron in width. One micron is less than one millionth of a meter. When the valleys are less than one micron wide, pockets of water vapor or gas accumulate in them by underwater evaporation or effervescence, just like a drop of water evaporates without having to boil it. Patankar said, "These gas pockets deflect water, keeping the surface dry."
The surface feature identified by the researchers could be used to reproduce a variety of materials on a mass scale, from anti-fouling surfaces for shipping to pipe coatings resulting in lower drag. The research team used a variety of materials with and without the key surface roughness and submerged them in water. It was observed that samples with the identified nano-scale roughness remained dry for up to four months. The scientists also reported that nature uses the same strategy of surface roughness in certain aquatic insects, such as water bugs and water striders.
The paper appeared in Scientific Reports.