A new way of texturing surfaces could make certain materials ultra-waterproof.
The new technique takes advantage of the fact that rougher, uneven textures cause water droplets to bounce off of them more quickly than smooth surface. And the less time water stays in contact with a surface, the drier that material stays. The new method could be used for many applications, including waterproof clothing and sports gear, as well as anti-icing tech for airplane wings.
It was developed by Kripa Varanasi, a mechanical engineer at MIT, and his colleagues, who used a high-speed camera to film a silicone wafer with a highly water-repellent coating being sprayed with water.
The scientists found that droplets that hit the surface evenly and then spread out symmetrically actually spent more time in contact with the surface than those that hit the surface unevenly.
So, the researchers created a new textured surface with small ridges that broke up the drops unevenly. The resulting smaller drops took less time spreading out on the surface before bouncing off of it. [Video: Hydrophobic Sand Underwater]
But it turns out the scientists weren't the first to discover this waterproofing strategy; nature had beaten them to it.
"We discovered that both the wings of the Morpho butterfly (Morpho didius) and the leaves of the nasturtium plant (Tropaeolum majus L.) have multiple superhydrophobic ridges, or veins, on a similar scale to our macro-textured surfaces," the authors write in the research article describing the new technique today (Nov. 20) in the journal Nature.
The new materials could have multiple applications. In addition to waterproofing sporting gear and clothing, the new approach could be used for keeping airplane wings from becoming icy and improving the aerodynamics of minuscule robots flying in the rain.
"We expect that this approach could be extended to surfaces exposed to freezing rain to prevent icing," the researchers write.
That's because the freezing of raindrops onto a surface takes time, so reducing the contact time between the surface and the rain could reduce frost accumulation.
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