An international team of scientists unlocked the anti-icing secret of polar bear fur, a discovery that could revolutionize ice-repellent technologies. The study, published as the cover story in the journal Science Advances, reveals that the composition of an oily substance called sebum in polar bear fur is responsible for its ability to repel ice, according to Phys.org.
The researchers performed a detailed chemical analysis of polar bear sebum, identifying cholesterol, diacylglycerols, and fatty acids as key components that distinguish it from the sebum found on other mammals. Among these substances, the absence of squalene—a compound found in large amounts in the fur of other mammals that swim frequently and in human hair oil—was noteworthy. This absence suggests that polar bears have evolved a distinct chemical makeup in their sebum that contributes to their fur's ice-repellent properties.
Julian Carolan, a doctoral candidate from Trinity College Dublin's School of Chemistry and the AMBER Research Ireland Centre and the first author of the journal article, led the investigation into this phenomenon. "We measured ice adhesion strength, which is a measure of how well ice sticks to fur; hydrophobicity, which dictates whether water can be shed before it freezes; and freezing delay time, which shows how long it takes for a drop of water to freeze at certain temperatures on a given surface," Carolan explained, according to Phys.org. "We then compared the performance of the polar bear hair with that of human hair and two types of specialist human-made ski skins."
The team's experiments revealed that unwashed, greasy polar bear fur exhibited lower ice adhesion compared to human hair and washed polar bear fur. "The sebum quickly jumped out as being the key component giving this anti-icing effect, as we discovered the adhesion strength was greatly impacted when the hair was washed," Carolan added, as reported by Il Giornale. "Unwashed, greasy hair made it much harder for ice to stick. In contrast, when the polar bear hair was washed and the grease largely removed, it performed similarly to human hair, to which ice sticks easily whether it is washed or greasy."
Dr. Richard Hobbs, a chemist at Trinity College Dublin and co-author of the study, commented on these findings. "This work not only represents the first study of the composition of polar bear fur sebum, but it also resolves the question of why polar bears don't suffer from ice accumulation," he said. "Despite having thick layers of insulating blubber and fur, and spending extensive periods in water at sub-zero temperatures, it seems that the fur grease provides a natural route for polar bears to easily shed ice when it forms due to the low ice adhesion on their fur."
The implications of this research extend beyond understanding polar bear ecology. "Our work shows that polar bear fur provides an alternative strategy to produce an anti-icing surface based on the blend of lipids present in their fur sebum or hair grease," Hobbs added. "We expect that these natural lipid coatings produced by the bear will help us to develop new, more sustainable anti-icing coatings that may replace 'forever chemicals' like PFAS that have been used as anti-icing coatings."
PFAS compounds are widely used in products designed to repel oil, heat, water, and ice but are increasingly controversial due to their environmental persistence and potential health risks. The polar bear's natural solution offers a promising alternative. As The Washington Post noted, "In the future, the polar bear's fur could inspire the development of new sustainable and chemical-free anti-ice coatings, helping to replace problematic 'forever chemicals' like PFAS."
Professor Bodil Holst from the University of Bergen, a senior author of the journal article, is exploring potential applications of their findings. "Our findings also help us understand the subtlety of the steps taken by Inuit people to optimize hunting strategies to mimic the polar bear method of still hunting," she said. "Inuit hunting stools are sometimes shod with polar bear fur on the feet to avoid noise when moving on the ice, while people also sometimes wear polar bear trousers, ensuring the entire contact area with the ice is covered in low ice-adhesion polar bear fur for optimal noise reduction."
The team's research measured the force required to remove ice from polar bear hair and found it to be a quarter of what was needed for human hair, as noted by New Scientist. Ice crystals adhered about four times more strongly to washed polar bear fur than to unwashed fur, indicating the role of sebum in maintaining the fur's ice resistance, according to Spektrum der Wissenschaft.
The researchers are considering the applications of their findings.
The article was written with the assistance of a news analysis system.