Polar bear hair recreated
Engineers are attempting to pinch the incredible insulative properties of polar bear hair.
Scientists in China have developed an insulator that reproduces the structure of polar bear hairs for real-world applications in the architecture and aerospace sectors.
Unlike the hairs of humans or other mammals, polar bear hairs are hollow.
The shapes and spacing of the cavities in the hair are responsible for the bears’ distinctive white coats, but they also are the source of remarkable heat-holding capacity, water resistance, and stretchiness, all desirable properties to imitate in a thermal insulator.
“Polar bear hair has been evolutionarily optimized to help prevent heat loss in cold and humid conditions, which makes it an excellent model for a synthetic insulator,” says co-senior author Shu-Hong Yu, a professor of chemistry at the University of Science and Technology of China (USTC).
“The hollow centres limit the movement of heat and also make the individual hairs lightweight, which is one of the most outstanding advantages in materials science,” says Jian-Wei Liu, an associate professor at USTC.
To emulate this structure and scale it to a practical size, the research team manufactured millions of hollowed-out carbon tubes, each equivalent to a single strand of hair, and wound them into a spaghetti-like aerogel block.
Compared to other aerogels and insulation components, they found that the polar-bear-inspired hollow-tube design was lighter in weight and more resistant to heat flow.
It was also hardly affected by water - a handy feature both for keeping polar bears warm while swimming and for maintaining insulation performance in humid conditions.
As a bonus, the new material was extraordinarily stretchy, even more so than the hairs themselves, further boosting its engineering applicability.
Scaling up the manufacturing process to build insulators on the meter scale rather than the centimetre one will be the next challenge for the researchers as they aim for relevant industrial uses.
“While our carbon-tube material cannot easily be mass produced at the moment, we expect to overcome these size limitations as we work toward extreme aerospace applications,” says Dr Yu.