As the days grow shorter and the wind blows colder, thoughts turn to how the heck to keep from freezing every time I leave my cozy, wood stove heated house. I sometimes think of the animals who don’t have it so lucky, and have to stay outside over the winter in dens or burrows, or especially anywhere near water.
Turns out, I should save my pity! Science has finally quantified how well the fur of animals like beaver and otter traps air to keep them warm in their semi-aquatic adventures – with an eye to developing tech that will keep us warm too.
The team of MIT engineers is particularly interested in creating wetsuits for surfers – whose amphibious sporting lifestyle requires a wetsuit that stays warm in the water, but that sheds water quickly when they leave it. They were intrigued by this problem because it had never been properly measured. Indeed, the actual mechanics of the air trapping in aquatic mammals, surmised to be the work of long “guard hairs” protecting the downier fur underneath, was unobserved. Once this process was cracked, the team would be one step closer to humanity producing “furry” heat retaining surfaces artificially.
The experiments first took a rigorous form of trial and error:
“To make hairy surfaces, [lead author and grad student Alice] Nasto first created several molds by laser-cutting thousands of tiny holes in small acrylic blocks. With each mold, she used a software program to alter the size and spacing of individual hairs. She then filled the molds with a soft casting rubber called PDMS (polydimethylsiloxane), and pulled the hairy surfaces out of the mold after they had been cured. […]
[The] researchers mounted each hairy surface to a vertical, motorized stage, with the hairs facing outward. They then submerged the surfaces in silicone oil — a liquid that they chose to better observe any air pockets forming.”
From their observations of the different amounts of air trapped by different hairy surfaces, the team then constructed a model that described the air-trapping in a mathematical manner. They turned these results into a scalable equation: hair density and length, and speed of dive can now be used to determine air trapping – and heat saving – capabilities. (This precision prevents the need for a “Cookie Monster” level of hairiness to maintain warmth.)
While I’m no surfer, I am a fan of aquatic mammals, and I’m fascinated at the science behind this innovation! I can’t wait to see the eventual application – in wetsuits and other fields, like industrial dip-coating. We still have so much to learn from Nature, and this just proves it.