A colorful breakthrough in cooling fabrics
As summer temperatures climb, most passive cooling fabrics are white because they reflect sunlight away from the body. But a team of researchers from Zhengzhou University in China and Adelaide University in Australia has developed a purple fabric that stays cooler than white cotton under direct sunlight, potentially opening the door to a new generation of colorful clothing designed to beat the heat. The research is published in the journal Small.
The fabric remained up to 6.2°C cooler than commercially dyed purple cotton and more than 4°C cooler than conventional white cotton in outdoor tests, according to a statement from Adelaide University. The breakthrough tackles a difficult problem: darker colors absorb more solar energy, and purple is especially challenging because its color comes from absorbing green light, one of the strongest parts of the solar spectrum.
How the cooling works
The fabric is made from microscopic fibers containing a purple metal-organic framework (MOF) and zinc oxide nanoparticles. These materials give the fabric its color while also helping it manage sunlight and heat. The study reports that the fabric reflects an average of 87.6% of solar radiation and emits 96.4% of mid-infrared radiation, allowing heat to escape through the atmosphere toward outer space. According to the research paper, solar reflectance is 90.1% in visible light and 90.7% in the near-infrared range.
The cooling relies on a phenomenon called radiative cooling. Earth's atmosphere is transparent to infrared wavelengths between 8 and 13 micrometers, so heat emitted in that range can pass straight through the atmosphere into outer space. This means radiatively cooled materials can even go below the ambient temperature because they are thermally coupled with deep space, which is about 3 degrees above absolute zero on average.
Tests using simulated skin showed that the fabric provided up to 8°C of cooling compared with uncovered skin, while white cotton produced a maximum skin temperature reduction of 4.6°C and conventional purple cotton only 2.8°C.
Practical features and limitations
Beyond its cooling performance, the fabric is lightweight, flexible, and can withstand significant stretching. It also allows water vapor, including perspiration, to pass through, making it comfortable to wear. The researchers say the fabric is water-repellent and retained its cooling performance after 50 washing cycles, and it maintained its optical performance after high-intensity UV aging equivalent to about 108 days outdoors.
The approach could potentially be adapted to other colors by using different MOFs with different optical properties, according to the researchers. The study was led by scientists at Zhengzhou University with involvement from Adelaide University.
Adelaide University professor Jun Ma, a co-author of the study, said the researchers wanted to prove that effective cooling did not have to mean giving up color. "We have traditionally had to make a choice between cooling performance and appearance," Ma said in a statement. "Our research shows that we can have both. We can make a fabric that looks purple, but at the same time reflects most of the sun's energy and releases heat very efficiently."
While the results are promising, a 2025 review questioned whether radiative cooling materials can move beyond theory into feasible applications, noting that production scalability remains an open question. Some companies are already commercializing radiative cooling for buildings, including US-based Skycool Systems, but similar applications for clothing are still in development.