America
This Indian-origin man helps keep surfaces dry underwater
Washington, Aug 19
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.