Penguins share many features with other birds despite their inability to fly. Especially the feathers are remarkable in terms of insulation and drag reduction. A new study by mechanical aerospace engineers from University of California Los Angeles (UCLA) reveals another secret: why penguin do not freeze over when coming out of the icy waters of the Antarctic. The new findings may help to prevent airplane hulls and especially wings from icing in the future.

Gentoo penguins are the most generalistic penguin species. They live all around Antarctica and now even breed on the continent. Picture: Michael Wenger
Gentoo penguins are the most generalistic penguin species. They live all around Antarctica and now even breed on the continent. Picture: Michael Wenger

Penguins and their ability to withstand the icy conditions of the Antarctic environment always have fascinated both tourists and scientists. These iconic little Antarctic ambassadors seem unaffected by low temperatures in both air and water. Especially when coming out of the Antarctic waters right into the freezing air, penguins do not turn into walking popsicles immediately. The secret of their success lies within the structure of the feathers. A research team led by Dr. H Pirouz Kavehpour from UCLAs Department of Mechanical and Aerospace Engineering has unraveled the mystery behind the water repellency of penguin feathers.

The water repellency of penguin feathers helps the animals to stay dry. Until now, it was attributed to the preen oil. However, the study by Alizadehbirjandi et al. has shown a more detailed picture now. Picture: Michael Wenger
The water repellency of penguin feathers helps the animals to stay dry. Until now, it was attributed to the preen oil. However, the study by Alizadehbirjandi et al. has shown a more detailed picture now. Picture: Michael Wenger

Conditions in the natural habitat of penguins favor the formation of macroscopic ice on many surfaces. It is common to find seals with little icicle hanging from their vibrissae or on their fur. However, penguins do not show no signs of icing even coming out of the water and standing in the wind with its sub-zero conditions. The water drops and droplets just run off the feathery surface and the penguins stay dry. UCLA-researchers Elaheh Alizadehbirjandi and Dr. Pirouz Kavehpour were fascinated by this ability and have used electron microscope scans on gentoo penguin feathers. They found rugged and jagged surfaces filled with nano-sized pores. Additionally, penguins coat their feathers with an oily substance originating from their preen gland. Both the specific surface texture and the hydrophobicity of the substance increase the contact angle of water drops to over 140°. Thus, water just slides off the surface and will not allow ice formation in even the coldest conditions. The team has presented their findings at the Annual meeting of the American Physical Society Division of Fluid Dynamics in Boston last November.

The team around Dr. Kavehpour not only investigated the feather of gentoos, but also compared them to feathers of magellanic penguins. This species lives north of the convergence, the biological boundary of the Antarctic. Thus, magellanic penguins usually do not have contact with icy conditions as their Antarctic relatives. The results of the investigation showed that the feathers of the northern penguin species have no nano-pores. Further, the oil of the preen gland has less water-repellent characteristics.

Magellanic penguin also inhabit the islands of the Falkland archipelago. There, they are direct neighbors of gentoo penguins. Picture: Michael Wenger
Magellanic penguin also inhabit the islands of the Falkland archipelago. There, they are direct neighbors of gentoo penguins. Picture: Michael Wenger

The researchers are now using their results to design an artificial surface with a minimal ice-forming ability, which could be interesting for the aircraft industry in the future.

Source: Science News, www.sciencenews.org