The temperature in Antarctica can nosedive to -135.8 degrees Fahrenheit, and yet penguins there manage not to ice over due to a combination of attributes that make them "superhydrophobic," according to new research.
Now that the super water repelling powers of these sturdy flightless birds have been determined, the techniques could be used in future to improve the design of airplane wings, flaps and rudders, which can collect ice and cause planes to crash.
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Researcher Pirouz Kavehpour, a professor in the Department of Mechanical and Aerospace Engineering at UCLA, first got interested in penguin feathers while watching a nature documentary.
"I noticed the penguins were coming out of very cold water, and sitting in very cold temperatures, and it was curious that no ice formed on their feathers," said Kavehpour, who presented his later research findings at the annual meeting of the American Physical Society's Division of Fluid Dynamics, which is being held this week in Boston.
For the study, he, penguin expert Judy St. Leger, and other researchers used scanning electron microscopy to analyze penguin feathers donated by San Diego SeaWorld.
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The scientists discovered that the feathers had tiny pores that trap air and make the surface incredibly water repellent. They also noticed that the penguins apply an oil, which is produced by a gland near the base of their tail, to their feathers. This one-two punch makes the feathers superhydrophobic.
When water meets such a surface, the droplets bead up and can roll off or be shaken away by the penguins. The droplets on the feathers also take on a spherical shape that delays ice formation. That is because heat has a hard time flowing out of the water droplet if it does not make much contact with the surface.
"Heat flow could be compared to traffic," Kavehpour explained in a press release. "If you have a freeway that turns into a tiny, two-lane road, the traffic will back up. Similarly, heat does not flow well from the large cross-section of the middle of the drop to the small cross-section where the drop makes contact with the feather."
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When the researchers compared the Antarctic penguin feathers with those from penguins hailing from warmer, more northerly climates, they found that the latter lack the small pores. The penguins from warmer regions even use a different type of preen oil that is not as water-repellant.
As for how the findings could be applied to airplane design, perhaps planes in future will be outfitted with similar superhydrophic pitted surfaces and lubricants to prevent ice formation. Currently, chemical de-icers are applied, but the process can be expensive, time consuming, polluting and flawed. Compare that to the ease of penguins, whose feathers naturally keep the iconic black and white birds from becoming living popsicles.
Kavehpour concluded, "It's a little ironic that a bird that doesn't fly could one day help airplane fly more safely."