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Super-Dry Surface Allows Water to Bounce Off Easily [Video]

Nov 21, 2013 03:43 AM EST

Massachusetts Institute of Technology researchers have developed a new material that lets water bounce off its surface very easily. The new butterfly-inspired, super-dry surface can be used in many industries, right from rainwear to airplane wings.

There is a theoretical limit on the time water droplets take to leave a surface. The latest study that included scientists at Boston University has shown that this threshold can be breached to create surfaces that can reduce the contact time by up to 40 percent.

That's not all. Usually, smooth surfaces are considered better water-repellents because they don't have room for water to cling-to. The new surface is wrinkled and yet enables water to bounce-off.

Inspired by Nature

Leaves of lotus and butterfly wings are some examples of superhydrophobic surfaces in nature. When a drop of water falls on a lotus leaf, it flattens like a pancake before recoiling and reforming into a drop that slides away.

To make an artificial water-repellent surface that is as good as a lotus leaf, one needs to reduce contact time. Conventionally, this is done by lowering the interaction between surface and droplets.

However, researchers have now demonstrated that increasing surface interaction can actually fasten the process by which water bounces-off the surface.

The new surface has ridges that disrupt a droplet's shape. "We've demonstrated that we can use surface texture to reshape a drop as it recoils in such a way that the overall contact time is significantly reduced," said James C. Bird, the paper's lead author from Boston University, according to a news release.

The wrinkled surface has reduced contact time; about 40 percent shorter than control surfaces.

Researchers also found that nasturtium leaves have veins on top, unlike other leaves, which break the symmetry of water droplets

Why design super-dry surfaces

Well, for one we'd have better rainwear.

Kripa Varanasi, one of the study authors from MIT, said that the process of creating superdry surfaces by creating ridges is more environment friendly than water-proof coatings.

Super-hydrophobic surfaces are not only important in preventing icing and corrosion in airplanes and ships, but also helps keep buildings from damage.

Ultra-dry textures can also help increase efficiency of turbine blades used in power plants.

"If you can make the blades stay dry longer, you get a bump up in efficiency," Varanasi said in a news release by MIT. "The new technique could also reduce corrosion on surfaces where droplets, especially if they are acidic or contain contaminants, contribute to degradation.

The study is published in the journal Nature.

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