Beavers and sea otters lack the thick layer of blubber that insulates walruses and whales. And yet these small, semiaquatic mammals can keep warm and even dry while diving, by trapping warm pockets of air in dense layers of fur. Inspired by these fuzzy swimmers, MIT engineers have now fabricated 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, published on July 29, 2016 in the journal Physical Review Fluids, provide a detailed mechanical understanding for how mammals such as beavers insulate themselves while diving underwater. The article is titled “Air Entrainment in Hairy Surfaces.” 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,” says Anette (Peko) Hosoi, Professor of Mechanical Engineering and Associate Head of the Department 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.” Dr. Hosoi’s co-authors include lead author and graduate student Alice Nasto, postdoc José Alvarado, and applied mathematics instructor Dr. Pierre-Thomas Brun, all from MIT, as well as former visiting researcher Marianne Regli, and Christophe Clanet, both of École Polytechnique, in France. The group’s research was motivated by a 2015 trip to Taiwan. Dr. Hosoi leads MIT’s STE@M (Sports Technology and Education at MIT), a program that encourages students and faculty to pursue projects that help advance sports technologies. In the summer of 2015, Dr.
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