Butterfly wings inspire ‘most waterproof’ material
06/12/2013
Adding tiny ridges to a silicon surface made water bounce off it 40% faster than the previous "limit”, according to Prof Kripa Varanasi, who said instead of using lotus leaves as inspiration they looked at the wings of the Morpho butterfly and the veins of nasturtium leaves.
The scientists copied the larger structures that increase the area of liquid touching the surface, but make the droplets bounce off faster by breaking each one into asymmetric pieces.
They wrote in the journal Nature: “The conventional approach has been to minimize surface-liquid interactions that can lead to contact line pinning; but even in the absence of any surface interactions, drop hydrodynamics imposes a minimum contact time that was conventionally assumed to be attained with axisymmetrically spreading and recoiling drops.
"We demonstrate that it is possible to reduce the contact time below this theoretical limit by using superhydrophobic surfaces with a morphology that redistributes the liquid mass and thereby alters the drop hydrodynamics. This allows us to reduce the overall contact time between a bouncing drop and a surface below what was previously thought possible.”
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