Researchers from Harvard University have developed and tested specific, patterned, nanostructured materials that reject supercooled water droplets before that water can freeze to a surface. When supercooled droplets hit smooth surfaces, the researchers found they spread out and freeze. That was not the case when the Harvard team applied the same tests to nanostructures created with patterns that reduced the surface area to which the water could adhere. Perhaps counterintuitively, that involved adding texture to the surface on a microscopic level. With their most successful tests, the researchers found a supercooled droplet would initially hit the surface and spread out, but instead of freezing, the droplets that hit the nanostructured pattern would then retract back into a sphere and simply bounce off.
The research tested materials and showed them to prevent ice formation down to -30C. Below that, ice did form, but did not adhere as well as it did to non-nanostructured surfaces and was considered easier to remove. The project began with a look at the legs of mosquitoes and water strider insects. The insects manage to keep dry thanks to an array of bristles that minimize surface area and repel water droplets. The research is now moving from controlled tests to real-world settings. The group hopes to be able to develop coatings best described as ice-preventive materials specifically designed for particular applications.
