A team at the University of Chicago’s Pritzker School of Molecular Engineering (PME) has developed a new fabric that could help people survive the worst impacts of heat, particularly in urban environments. This new textile reduces heat from both the sun and thermal radiation from nearby buildings, and has the potential to be used in clothing, building and car design, and food storage.
Cooling fabrics currently in use for outdoor sports work by reflecting the sun’s light in a diffuse pattern. In urban heat islands, however, the sun is only one source of heat, as thermal radiation is also emitted from buildings, pavement and vehicles. This required the team to address the challenge of creating one material capable of protecting wearers from these various heat sources.
“Solar is visible light, thermal radiation is infrared, so they have different wavelengths. That means you need to have a material that has two optical properties at the same time. That’s very challenging to do,” said co-first author Chenxi Sui, a PhD candidate at PME. “You need to play with material science to engineer and tune the material to give you different resonances at different wavelengths.”
They created a textile composed of a top layer that selectively emits through the atmospheric infrared radiation window, a silver nanowire layer to reject incoming thermal radiation, and a wool bottom layer to move heat from the skin to the middle layer. A thicker version of the fabric protected by an invisible layer of polyethylene could be used on the sides of buildings or cars, lowering internal temperatures and reducing the cost and carbon impact of air conditioning. Potentially, the material could be used to transport and store foods that would otherwise spoil in the heat, reducing the need for refrigeration.
In tests in Arizona, the material kept 2.3 degrees Celsius cooler than the broadband emitter fabric generally used for outdoor endurance sports and 8.9 degrees Celsius cooler than the commercialized silk often used for summer clothing.