Move aside Harry Potter, science has invisibility cloaks too. The non-magical version was inspired by polar bear fur and works by having, excellent thermal insulating properties. Polar bear hair has a hollow core which effectively prevents the infrared emission, or heat signature, of the polar bear from escaping the fur. This helps the bear retain its heat and stay warm. Because of this efficient reflection of heat, the fur also maintains the same temperature as the air around it, making the polar bear relatively “invisible” under an infrared camera.
Researchers from Zhejiang University have produced a biomimetic fiber, a textile with the same excellent thermal properties. The key to making the fiber is a “freeze-spinning” method where a silk-water fiber solution is frozen as it is spun. The ice crystals form voids within the fiber that are later removed to leave behind silken fiber comprised of hollow cavities. Importantly, this fabrication method allows for alignment of the internal cavities to ensure the structural integrity of the fibers, preventing them from being brittle.
The researchers tested these fibers by cloaking rabbits with a blanket of the material. When imaged with an infrared camera, only the exposed parts of the rabbit were detectable. The blanket’s external temperature matched the surrounding environment, thus making the cloaked parts of the rabbit partially invisible. While it is no true invisibility cloak, this method of producing “infrared-invisible fur” provides an exciting avenue for designing not only military tech, but also extremely efficient winter gear to defend against extreme cold environments.