Polar bears fur show almost no leakage of heat, due to a pore-like structure of the hair which form an air package under the fur. Bo HAO and colleagues at Zhejiang University have injected a 5 % fibroin solution into an iced spinning machine, forming fibers. In order to remove the ice, the fibers were then freeze-dried, resulting in fibers with an orderly distribution of narrow holes. When these fibers were worn into a miniature sweater, the surface temperature of a rabbit dressed in such sweater was locked between -10 ℃ to 40 ℃, providing a perfect heat stealth effect. Thermal conductivity of polar bear’s hair was found to be 27 W/K, whereas it was 19 W/K for the best among the bionic fibers produced. The group claims to be able to produce 1 meter of such fabric in two hours.

CAS news release, March 6, 2018