Breakthrough Fabric Offers Cooling Relief Amidst Escalating Global Heatwaves

2024 is only half over yet the world has already witnessed unprecedented heatwaves, with cities in Mexico, India, Pakistan, and Oman experiencing temperatures soaring to nearly 50 degrees Celsius (122 degrees Fahrenheit). As global temperatures rise and urban populations swell, cities have turned into "urban heat islands," where densely packed conditions and thermal radiation from pavements and skyscrapers trap and intensify heat.

With projections indicating that 68 percent of the global population will live in urban areas by 2050, this escalating heat poses a severe and growing threat.

A new paper published in Science by researchers from the UChicago Pritzker School of Molecular Engineering (PME) introduces a groundbreaking wearable fabric designed to help urban residents withstand extreme heat caused by climate change. The fabric has versatile applications, including clothing, building and car design, and food storage, potentially offering life-saving relief.

In rigorous tests conducted in Arizona—where extreme heat is a regular occurrence—the innovative material maintained temperatures 2.3 degrees Celsius (4.1 degrees Fahrenheit) cooler than fabrics used in outdoor endurance sports and a remarkable 8.9 degrees Celsius (16 degrees Fahrenheit) cooler than commercial silk commonly used in summer apparel. This significant temperature reduction can help mitigate the heat-related hospitalizations and fatalities that have plagued urban centers globally this year.

Notably, cooling fabric for outdoor posts exists, reflecting sunlight diffusely and preventing glare. However, in urban heat islands, the sun is just one heat source. Thermal radiation from buildings and pavements bombards city-dwellers from all sides, making many materials ineffective in real-world conditions.

"People normally focus on the performance or the material design of cooling textiles," said co-first author Ronghui Wu, a postdoctoral researcher at PME. "To make a textile that has the potential to apply to real life, you have to consider the environment.

Creating a material that protects against both solar and thermal radiation presented a significant engineering challenge.

"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."

Cooling often exacerbates climate change due to the carbon footprint of air conditioning and refrigeration: Sui notes that “civilization actually uses about 10 to 15 percent of the energy in total just to make ourselves feel comfortable wherever we go.” Strikingly, the overwhelming majority of households in the United States and Japan have air conditioning—about 90 percent—whereas in India and parts of Africa just five percent of homes have cooling systems to beat the heat.

The PME team's new textile, now under provisional patent, offers a passive cooling system that can reduce reliance on energy-intensive cooling methods. Beyond clothing, a thicker version of the fabric could be used on buildings and cars, lowering internal temperatures and reducing air conditioning costs and carbon emissions. Additionally, the material could help transport and store perishable foods, minimizing the need for refrigeration.