Nanostructure developed by Shenzhen University researchers reflects all rays highly effectively
Researchers at Shenzhen University (https://en.szu.edu.cn) have developed a new special film whose structure resembles that of butterfly wings. It appears colored even though it does not contain any pigments. The film repels infrared rays from the sun, so it has a cooling effect on the objects to which it is stuck. They could be used on facades, roofs, cars and elsewhere to reduce the technical cooling power provided by air conditioning systems. Details can be found in “Optica.”
Cooling foil protects climate
“Buildings use large amounts of energy for cooling, and running air conditioners in e-cars can reduce range by more than half. Our cooling films could help advance climate neutrality,” says research team leader Guo Ping Wang.
According to the researchers, the films they developed lower the temperature by about two degrees Celsius below the ambient temperature. Also, the surface of the blue version of the film was about 26 degrees colder than conventional car paint of the same color when exposed to sunlight. “With our new films, excellent cooling performance can be achieved regardless of the desired color, saturation or brightness. They could even be used in textiles to make clothing that is comfortable to wear in hot temperatures in any color,” Wang said.
Function through texture
A car with blue paint appears blue because it absorbs yellow light and reflects blue light. The large amount of light that is absorbed warms the car. The wings of the blue morpho butterfly appear blue because of their nanostructure. The design of the cooling nanofilm mimics these structures to create rich colors that do not absorb light or heat.
The film’s color is determined by the way components within its multilayered structure reflect light. For example, to produce blue, the material is designed to reflect yellow light in a very narrow angular range, while blue light is scattered over a large area.
Photo: Blue morpho butterfly: Bionic cooling foil based on it (Image: Wanlin Wang, en.szu.edu.cn)