New cooling materials can be created in different colors
shen chingchen
Colorful materials made of wood have the property of becoming cool even when exposed to direct sunlight, so they can be used to decorate the exterior of buildings and reduce the temperature inside without using air conditioning.
Most materials absorb a combination of ultraviolet, visible, and infrared light, so they warm up when exposed to sunlight, but instead reflect these wavelengths, which, in turn, heat the heat within the material. Some have a cooling effect as they radiate the area. Atmosphere to space as infrared rays.
Adding colored pigments to such materials usually increases the amount of light they absorb, but Silvia Vignolini of the University of Cambridge and her colleagues have created red, green, or blue versions that retain their cooling effect. i found a way to do it. The ingredients are derived from wood in the form of two types of cellulose.
The chemical bonds in cellulose are particularly well-suited for emitting the right kind of infrared radiation that provides a cooling effect. Cellulose nanocrystals, on the other hand, which can be extracted from sources such as wood pulp and cotton, produce iridescent colors without pigments. This effect is similar to how a soap bubble exhibits a prismatic color on its surface by scattering different wavelengths of light in different directions.
Vignolini and her colleagues combined these properties by layering nanocrystals on highly reflective sheets made from a cellulose derivative called ethylcellulose. By adjusting the placement of the nanocrystals, we created versions of this film in red, green, and blue, and found that she averaged 3°C below ambient temperature during the day.
While this early version is promising, Vignolini says more work is needed to make it a viable decoration, as the colored layers are susceptible to environmental influences such as weather. “It needs to be durable enough to transition from here to applications on walls and devices,” she says.
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