Polar bears are the iconic animals of the Arctic and an extraordinary example of nature adaptation.
Indeed, polar bears are the biggest land-based carnivores on Earth but, curiously enough, they are considered as marine mammals because they spend most of their life on the sea ice and are excellent swimmers. In wintertime the average temperature in the Arctic regions goes between -34 and 0 Cº with minimum picks that reach -50 Cº, while during summer time the temperature ranges from -10 to 10 Cº.
The sea ice of the Arctic region is one of most hostile environment on the planet but not for polar bears. In fact, the body features of polar bears have adapted to perfectly tolerate extremely cold temperatures, allowing them to move across snow, ice and cold water. Indeed, a thick layer of fat, which shields low temperatures, protects these animals. However, the fat layer is not the only barrier against low temperature. Polar bears are coated with a perfectly designed white fur, which ensures both camouflage and thermal isolation.
But which is the secret of this perfectly designed white fur and how does it contribute to thermal isolation? The answer resides in the hair of these animals, and in particular in its simple but smartly designed microstructure. Indeed, the polar bear hair is non-wettable and its shape reminds of an empty tube or cable, meaning that it is characterized by a hollow structure. This feature might seem trivial, but it actually plays a key role in facing the extremely cold Arctic environment. In fact, this particular shape is able to trap small amount of air inside the hollow structure. Air is a poor thermal conductor and therefore it acts as a thermal barrier within each hair.
Already during the Stone Age, our ancestors understood the thermal insulation capacity of the animal fur, which became crucial for their survival during harsh and cold seasons. In the recent years, the thermal isolation properties of the polar bear hair have attracted the interest of the scientific community for the design of new innovative material with enhanced thermal isolation properties. Thermal insulation is critical for energy management, such as controlling of energy waste and use. The possibility to develop new and more efficient material with enhanced thermal isolation properties could be beneficial in a wide range of applications. In fact, biomimetic hollow structure inspired by polar bear hair represents one of the most promising candidates for numerous applications in different sectors.
In particular, nowadays, there is an increased need for better thermic isolated buildings in order to reduce energy use. Additionally, the textile sector can benefit from the design of new polar bear-inspired cloths and even the automotive and space industry can benefit from better thermal isolation materials.