Engineers from Harvard University have designed nanostructured materials that repel water droplets before they have had a chance to freeze.
The development could lead to a new way to keep aircraft wings and powerlines free of ice during the worst winter weather.
’Freezing starts with droplets colliding with a surface,’ explained Harvard professor of materials science Joanna Aizenberg, who led the research into the new materials. ’But very little is known about what happens when droplets hit surfaces at low temperatures.’
To gain a detailed understanding of the freezing process, the researchers watched high-speed videos of supercooled droplets hitting surfaces that were modelled after those found in nature.
They saw that when a cold droplet hits a nanostructured surface, it first spreads out but then retracts to a spherical shape − after which it bounces back off the surface before ever having a chance to freeze. By contrast, on a smooth surface without the structured properties, a droplet remains spread out and eventually freezes.
The researchers then created surfaces on several materials with various geometries and features, which also prevented the formation of ice − even down to temperatures as low as -25 to -30°C.
The researchers anticipate that, with their improved understanding of the ice-forming process, a new type of coating integrated directly into a variety of materials could soon be developed and commercialised.