Polar bears are almost invisible to infrared cameras, why? What are the reasons?

As inspiration for this design, experts and scholars from Zhejiang University developed a bionic fiber and successfully enabled a rabbit to achieve "thermal invisibility". The results of this scientific research will also allow people to wear warmer clothes and even allow soldiers to wear "stealth uniforms." Different from "optical invisibility", "thermal invisibility" refers to the invisibility effect achieved due to the infrared thermal imaging equipment's inability to detect the heat emitted by organisms.

According to statistics, under a microscope, polar bear hair appears as a translucent hollow porous material, which is an excellent thermal insulation fiber. Notably, their hair also reflects sources of infrared-induced radiation, making polar bears essentially invisible to thermal surveillance cameras. What are the characteristics?

In order to better imitate this structure, Bohao's team melted mulberry silk into water to make a spinning aqueous solution with a moisture content of 95%. Later, the mixed material is gradually introduced into an ultra-low temperature system using an injection needle, producing refrigerated porous structural fibers with a diameter of approximately 200 μm and containing ice crystals. Finally, through low-temperature drying, the ice crystals in the fiber are lifted, leaving many orderly layered holes.

They covered a rabbit with knitted fabric and used a thermal camera to observe. The data shows that in conditions ranging from -10°C to 40°C, the camera is basically unable to detect the heat generated by the rabbit's body.

It is reported that Sylvain Deville, a scientist from Cavaillon, France, has previously used the same ice template method to produce porous fibers. However, Dwyer believes that Zhejiang University has demonstrated a stronger ability to manipulate fiber structures.

In scientific research, Bohao's team also added bionic fibers to carbon nanotubes to create a new electric heater fabric. At a working voltage of 5 amps, the electric heater fabric can fully automatically rise from 24°C to 36°C in one minute. Although the heated fabric will no longer have the "thermal invisibility" effect, it has become "winter clothing" with better cold protection and warmth.