We built airplanes after centuries spent studying birds. So it's fitting a new invention that might make flying safer, faster and gentler on the environment was also inspired by a creature—though this time the muse was much more terrestrial: the slug.
Chihiro Urata and a team of researchers at the National Institute of Advanced Industrial Science and Technology in Japan have mimicked the earth-hugging animal to create a long-lasting coating for plane wings so slippery that ice can't stick to it. It could make the ice-fighting chemicals sprayed on planes between flights to ensure safe takeoff—and the delays while passengers wait while these deicers are applied—a thing of the past.
"I came upon this idea while observing real slugs while gardening," says Urata. "Slugs eat baby plants, and that annoyed me. When we got rid of them, I found that there were no dirty slugs, even though they live in the soil during the daytime. And I found mucus on their skin, which repels dirt; the dirt slides off."
The team combined different types of silicone into a gel that could be spread on wing pieces and then hardened at 212 degrees during manufacturing. When the plane flies through temperatures below freezing, slippery oils come to the surface and any ice slides off. When the air warms up, the oils retreat into the film. "The oil does not want to stay in the coating when it's cold," says Urata.
The team has worked on the material for two years, publishing along the way. Now it's ready for real-life testing. Urata says the institute also plans to try the anti-ice coating on road signs and solar panels. A different formulation could be used on boat hulls to keep them free of barnacles and other hangers-on. The researchers presented their work Wednesday in San Diego at the national meeting of the American Chemical Society.
The film holds together thanks to polydimethylsiloxane, the same chemical compound that puts the silliness in Silly Putty, making it bounce like a ball yet flow like a very slow liquid. The silicon polymer turns up in all sorts of other materials too, including caulks, shampoos, lotions, breast implants and even food—some fast-food chains add it to their frying oils to prevent foaming. Most research has found it safe for humans and the environment.
"I do not think the coating is hazardous," says Urata. "We use silicone oil.... Silicone oil or its derivatives are widely used in daily life."
If the treatment proves safe, it would be an improvement over the sprays currently used to free plane wings of ice. Not only would it work faster, but it also would be better for the environment. According to the Environmental Protection Agency, these compounds mostly drip off at the airport. If they get into water, microbes break them down and consume large amounts of oxygen in the process, which kills fish and other animals. To prevent this, a 2012 EPA rule required new large airports to capture 60 percent of the deicer they used. At the time, the agency found that the fluid used on a single plane could rob water of the same amount of oxygen as 1 million gallons of raw sewage.
The film could make those sprays unnecessary—and produce an unusual situation where industry and environmentalists slug it out and everyone's happy with the results.
Uncommon Knowledge
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