A team of engineers led by an Indian-origin scientist has identified ways to keep a surface dry for a longer period of time when submerged in water -- a finding that may save billions of dollars in a variety of industries.
The team of the US-based Northwestern University engineers, led by theoretical mechanical engineer Neelesh A. Patankar, is the first to identify the ideal surface "roughness" needed in the texture to keep it dry under water for a longer period of time.
"The trick is to use rough surfaces of the right chemistry and size to promote vapour formation, which we can use to our advantage," said Patankar.
The valleys in the surface roughness typically need to be less than one micron in width, the researchers found. One micron is less than one millionth of a metre.
When the valleys are less than one micron wide, pockets of water vapour or gas accumulate in them by underwater evaporation or effervescence, just like a drop of water evaporates without having to boil it.
"These gas pockets deflect water, keeping the surface dry," he said.
The surface feature identified by the engineers 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 researchers used a variety of materials with and without the key surface roughness and submerged them in water. It was found that samples with the identified nano-scale roughness remained dry for up to four months.
The researchers 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 the journal Scientific Reports.
