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Super-Slick Material Stops Ice from Forming

The first application of a novel water-repellent material from Harvard could be low-energy freezers.

A super-slick new material, inspired by the treacherous mouth of the carnivorous pitcher plant, has been developed by researchers at Harvard University.

For years researchers had been trying to use superhydrophobic materials—materials with microscopic structures that repel water—to prevent icing (see “Surfaces that Keep the Ice Away”). But in some conditions, such as high humidity, existing superhydrophobic materials can have the opposite of the intended effect, causing more ice to form and adhere more strongly than it would on an untreated surface. The materials can also be fragile, losing their slipperiness if they’re scratched.

Harvard researchers led by Joanna Aizenberg, a professor of chemistry and chemical biology, turned to nature for an alternative approach, taking inspiration from the pitcher plant, whose surfaces are so slick that ants can’t even cling to them (see video below).

As with the previous superhydrophobic materials, the ones developed by Aizenberg involve nanostructured surfaces. But these structures are chemically modified so that they adhere to a specific lubricant. While the pitcher plant uses water to form a slick surface, the Harvard researchers use a variety of lubricants. The lubricant clings to the nanostructures and forms an extremely thin liquid film on the surfaces that is perfectly smooth, far more so than any solid surface could be, Aizenberg says. What’s more, if the material is scratched, the liquid flows over the scratch and the material maintains its slipperiness.

If commercialized, the material could reduce or eliminate defrost cycles in freezers, which accounts for about a quarter of the appliance’s total energy consumption. Initial tests of actual freezer components showed that the material can reduce defrosting energy consumption by 40 percent, says Aizenberg. She expects that figure to go up as the researchers optimize the system.

Freezers may be the first application of the technology, but it could also work for larger applications like airplanes, decreasing the need for time-consuming and expensive de-icing treatments. Likewise on wind turbines, where ice can cause them to stall and stop generating electricity. Ice can take whole wind farms offline and wreak havoc on the grid in places such as Colorado, where wind power now accounts for a large fraction of the total electricity supply.

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