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Bouncing drops make for smarter rainwear

Centre-assisted recoil from butterfly wing structures repels drops faster.

The surface was inspired by butterfly wings, which have minuscule veins on their surface that have the same drop-busting effect (Source: Adam Paxson, Kyle Hounsell, Jim Bales, James Bird, Kripa Varanasi )

Repulsive surface Scientists say they have found a way to make raindrops bounce faster off surfaces, opening the way to new water-resistant materials from clothing to aircraft wings.

Reporting in the journal Nature, a team at Boston University and the Massachusetts Institute of Technology (MIT) say they have slashed the amount of time a water drop stays in contact with a surface.



To minimise that time, materials scientists have been focussing their efforts on repellent, or hydrophobic, chemicals that make surfaces less adhesive for water.

But the new study takes a physical approach.



"The upshot is that the surface stays drier longer if this contact time is reduced, which has the potential to be useful for a variety of applications," says James Bird, an assistant professor of mechanical engineering at Boston.


Contact times with it were 40 per cent shorter than for a non-treated surface, and the scientists hope to boost this to as much as 80 per cent.

According to the authors, the texture could be replicated in other materials too - a milling tool could do the same on steel or aluminium, and a drop-splitting surface could be made for fabrics.

One early area of use could be in airplane wings. Exposure to water droplets at high altitudes boosts the risk of dangerous ice build-up.



Tags: nanotechnology