Chinese scientists have developed a fiber that mimic the structure of polar bear hairs. Textiles that can mimic polar bear hair’s IR-reflecting abilities might be useful in stealth applications, such as concealing soldiers. Polar bears’ hair has a hollow core, which reflects back IR emissions from the body. This structure not only helps prevent heat loss and keeps the bears warm in Arctic environments but can conceal the bears from thermal imaging cameras used in many night-vision devices.

Previous attempts to make synthetic versions of the hair produced fibers that were too weak to be practically useful. But the Chinese used a freeze-spinning method to make fibers that are porous, strong, and highly thermally insulating. They consist of fibroin, a protein found in silk, along with a small amount of the polysaccharide chitosan.

Researchers slowly squeezed a viscous, watery mixture of these materials through a cold copper ring, forming a frozen fiber that contained flat ice crystals. Freeze-drying the fibers removed the ice by sublimation to produce strong fibers about 200 micrometers wide with up to 87 per cent porosity.

After varying conditions such as the viscosity of the mixture and the temperature of the ring, they found that running the process at minus100 degree Celsius produced pores about 30 micrometers across, which offered the best balance between strength and thermal insulation.