Large oceangoing creatures, like whales and seals, keep warm with thick layers of blubber. But smaller mammals like beavers and otters have a different method of insulation: Their dense fur, which traps warm air bubbles to separate their body from cold waters. MIT engineers have devised a wetsuit featuring a similar hairy layer made of rubber to insulate divers and surfers.
The researchers looked at beavers and otters because the small mammals stayed warm while remaining nimble and agile, key traits for wetsuit material. Their pelts also offered clues for how to keep surfers warm while submerged yet quickly shed water when they pop up on their boards. While the current understanding of their hair theorizes longer "guard" fur trapping air in the dense "underfur" beneath it, the exact mechanics were unknown, requiring further research by the engineers.
Their results, published in the journal Physical Review Fluids, found that the spacing of each individual hair and the animal's diving speed affected how much air a surface would trap. They simulated the fur strands as tubes in a computer equation, resulting in a mathematical model to trapping different amounts of air, and thus, warmth.
"We have now quantified the design space and can say, 'If you have this kind of hair density and length and are diving at these speeds, these designs will trap air, and these will not.' Which is the information you need if you're going to design a wetsuit," associate head of the mechanical engineering department at MIT and co-author of the study Anette (Peko) Hosoi told MIT News. "Of course, you could make a very hairy wetsuit that looks like Cookie Monster and it would probably trap air, but that's probably not the best way to go about it."