Rebecca Tan | March 8, 2016
Nature is a rich source of inspiration for scientists studying superhydrophobic, or water-repelling, materials. The rough texture of lotus leaves, for example, have served as the basis for the design of stain-resistant clothing. Similarly, the ability of penguins to survive in cold and wet environments is thought to be due to the superhydrophobic nature of their feathers which would cause water to slide off before ice has had a chance to form.
However, superhydrophobic surfaces are known to function poorly precisely under cold and wet conditions. When humidity is high, the rough structure of superhydrophobic materials encourages the condensation of water which quickly turns into a layer of ice, while the adhesion strength of ice increases at ultralow temperatures, making it harder for ice that has been formed to slide off.
To better understand the anti-icing properties of penguin feathers, a team of researchers at Beihang University used scanning electron microscopy to study the microstructure of feathers from Humboldt penguins (Spheniscus humboldti).
The feathers had a hierarchical structure, with tiny hooks arranged at regular intervals on larger barbules that were in turn arranged on even larger barbs. The hooks formed a wrinkled three-dimensional network that effectively prevented water from soaking through.
“We found that the air-infused microscale and nanoscale hierarchical rough structures endow the body feathers of S. humboldti penguins with icephobicity,” study corresponding author Dr. Wang Jingming told Asian Scientist Magazine.Mimicking the structure of the feathers with polyimide nanofibers, the researchers developed a membrane where the fibers were spaced a few micrometers apart. The membrane was shown to be highly water-resistant, even to microdroplets that had been cooled to -5°C.
“Because of its excellent electrical insulation and icephobicity, the polyimide nanofiber membrane could be used in applications such as ice-proof coatings for electrical cables,” Wang explained.The researchers plan to further improve the anti-icing properties of their artificial feathers by studying the packing style of natural penguin feathers, another decisive factor determining their anti-icing properties.
The article can be found at: Wang et al. (2016) Icephobicity of Penguins Spheniscus Humboldti and an Artificial Replica of Penguin Feather with Air-Infused Hierarchical Rough Structures.