Beaver-inspired wetsuits in the offing

Inspired by hairy, semiaquatic mammals such as beavers and sea otters, MIT scientists are developing wetsuits that would keep deep sea divers dry and warm underwater.
Beavers and sea otters lack the thick layer of blubber that insulates walruses and whales. Yet these small, semiaquatic mammals can keep warm and even dry while diving, by trapping warm pockets of air in dense layers of fur.
Scientists at Massachusetts Institute of Technology (MIT) in the US are fabricating fur-like rubbery pelts and used them to identify a mechanism by which air is trapped between individual hairs when the pelts are plunged into liquid.

The results provide a detailed mechanical understanding for how mammals such as beavers insulate themselves while diving underwater. The findings may also serve as a guide for designing bioinspired materials - most notably, warm, furry wetsuits.
"We are particularly interested in wetsuits for surfing, where the athlete moves frequently between air and water environments," said Anette Hosoi, a professor at MIT.
"We can control the length, spacing, and arrangement of hairs, which allows us to design textures to match certain dive speeds and maximize the wetsuit's dry region," said Hosoi.

Semiaquatic mammals, including beavers and sea otters, trap, or 'entrain' air in their fur.

The animals are covered in two types of fur: long, thin "guard" hairs, that act as a shield for shorter, denser underfur.
Biologists have thought that the guard hairs keep water from penetrating the underfur, thereby trapping warm air against the animals' skin.
The team fabricate precise, fur-like surfaces of various dimensions, plunged the surfaces in liquid at varying speeds, and with video imaging measured the air that is trapped in the fur during each dive.
From these experiments, it appeared that the spacing of individual hairs, and the speed at which they were plunged, played a large role in determining how much air a surface could trap.

Researchers then developed a simple model to describe this air-trapping effect in precise, mathematical terms.
To do this, they modeled the hair surfaces as a series of tubes, representing the spaces between individual hairs.
They can now accurately predict how thick an air layer will surround a hairy surface, based on their equation.