Furry, Otter-Inspired Wetsuits Could Keep Surfers Warm

Semiaquatic mammals like beavers and sea otters keep warm and even dry while diving by trapping warm pockets of air in dense layers of fur. Inspired by these furry swimmers, MIT engineers have fabricated fur-like rubbery pelts and used them to identify the mechanism by which air is trapped between individual hairs when the pelts are plunged into liquid. Their findings may serve as a guide for designing bio-inspired materials like warm, furry wetsuits. "We are particularly interested in wetsuits for surfing, where the athlete moves frequently between air and water environments," says Anette Hosoi, a professor of mechanical engineering. "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." To make hairy surfaces, the team first created several molds by laser-cutting thousands of tiny holes in small acrylic blocks. With each mold, a software program to alter the size and spacing of individual hairs was used. The team 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.

Transcript

00:00:00 Inspired by hairy semi-aquatic mammals such as beavers and sea otters, a group of MIT engineers are fabricating fur-like rubbery pelts to learn how these mammals stay warm, and even dry, while diving under water. The group's research was initially motivated by a visit to a company who manufactures wetsuits. The company was interested in developing materials that would keep surfers warm and nimble while they

00:00:26 move in and out of the water. So our first thought was to take inspiration from biological systems, and we started looking at animals that are small and agile, but have to survive in Arctic environments and spend part of their time underwater and part of their time on land. One of the interesting things we learned about these marine mammals, is for small mammals that can't carry around a lot of blubber

00:00:47 but still need to maintain warmth, have a very specialized fur that traps air when they dive under water. And so what we're interested in doing is trying to understand what parameters of their fur, how fast they're diving, the properties of the liquid, how do these all come together to inform us how the air gets entrained? For their experiments, the team fabricates precise fur-like surfaces of various dimensions using molds and a soft casting rubber.

00:01:15 They then plunge the surfaces in liquids with varying viscosity and at varying speeds. Then with video imaging, they're able to measure the amount of air that is trapped in the fur during each dive. What they found was the spacing of individual hairs and the speed at which they were plunged play a large role in determining how much air a surface could trap. Based on these findings, the team developed a simple model

00:01:38 to describe this air trapping effect in precise mathematical terms that can be applied to various material's manufacturing processes. For example, wetsuits are now made of thick neoprene rubber. But what if we used a much more lightweight material, something with a hairy texture? And instead of using rubber we're using air for insulation, and it could be a lot more lightweight and still effective in water.

00:02:00 Beyond that, I think textile design is turning into a really interesting field right now. We have a lot of new manufacturing techniques. We have a lot of new materials that enable us to build new fabrics that can have specially tailored thermal properties, that can have specially tailored sensors. I think all of this ties into these ideas about quantified self, and sort of the new types of clothing that's going to be available to us in the upcoming years.

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