Being outside during a heat wave can be sweaty and uncomfortable, and it can even be harmful to your health. But scientists have come up with an innovation that they believe can provide relief: clothing that physically cools the body.
Researchers at the University of Massachusetts Amherst have developed a flexible, chalk-based coating that can be added to fabrics. In tests in the scorching summer heat, they found that it lowered the temperature under clothing by up to 8 degrees Fahrenheit compared to air, and by up to 15 degrees compared to untreated fabrics.
The innovation is one of many attempts to turn people’s clothing into a tool for combating extreme heat, which is becoming increasingly severe as humans continue to burn fossil fuels that warm the planet. Heat is the deadliest type of extreme weather, causing heat exhaustion and even heat stroke, a potentially fatal illness in which the body loses the ability to cool itself.
The UMass researchers say they wanted to develop a way to cool textiles using an environmentally friendly material. Inspired by traditional limestone plasters used to cool homes in hot climates, they coated textile tiles with particles of calcium carbonate, the main component of limestone and chalk.
According to new research, currently undergoing peer review and presented this month to the American Chemical Society, the coating is able to reflect the sun’s energy back into the atmosphere while allowing the wearer’s natural body heat to escape.
“We start with your cotton T-shirt … and we just apply this coating to one or both sides of the fabric,” Trisha L. Andrew, a chemist and materials scientist at UMass, told CNN. “The coating is completely surface level. It doesn’t penetrate the cotton fibers or alter them,” she added.
According to the scientists, the coating can be applied to almost all commercially available fabrics and is also machine washable.
“Without any power supply, we can reduce the degree to which a person feels hot, which could be a valuable resource as people struggle to stay cool in extremely hot environments,” Evan Patamia, a doctoral student at UMass who worked on the innovation, said in a statement.
Cooling fabrics aren’t a new invention, but according to a 2023 scientific review of cooling fabric research, previous designs often relied on rigid structures, complex manufacturing processes, and electrical components, making them uncomfortable to wear and expensive.
UMass’ development is part of a growing body of research into cheaper, more comfortable and scalable alternatives as the threat of extreme heat increases around the world.
Scientists at RMIT University in Melbourne, Australia, have used tiny particles called nanodiamonds to coat cotton fabrics, reducing the temperature by as much as 3 degrees Celsius (5.4 Fahrenheit) compared to untreated cotton, a recent study found.
This may not sound like a big deal, but it makes “a difference in long-term comfort and health outcomes, and in practical terms it could be the difference between turning the air conditioning off or on,” Shadi Houshyar, project leader and senior lecturer at RMIT, said in a statement.
Research from RMIT University has shown that using cooling materials can lead to energy savings of 20 to 30%, by reducing the use of air conditioning, a highly polluting cooling technique that has many damaging effects on the climate.
Nanodiamonds may sound expensive, but researchers say they are not the same as the diamonds used in jewelry. “They are actually cheap to make,” Houshyar said.
There is still room for improvement, she added. For example, they found that the efficiency of the nanodiamond dust decreased after the dust was washed multiple times.
The nanodiamonds work in a similar way to the limestone particles that UMass uses, Houshyar told CNN. The principle of these studies is the same, she said, using nanoparticles to transfer heat away from the body.
Houshyar, who has been researching protective clothing for more than a decade, said the manufacturing process UMass is using shows promise, but they need to figure out how to scale it up and keep costs down.
Cooling fabrics need to be affordable, she said. “If the cost is three times the cost of the normal fabric, it’s not going to be enough for everyone to use it.” It’s often the poorest people who are most vulnerable to extreme heat and have the least access to cooling technologies.
As more products come to market, “there are a lot of opportunities in this space to scale it and make it available to everyone,” Houshyar added.
UMass’ Andrew said her team has been limited by the size of their lab equipment so far. But through a new startup company, they plan to pilot production, making treated fabric sheets that are 5 feet wide and 300 feet long.
The cost of the raw materials for the coating is “low to manageable,” Andrew said, but he accepted that the overall price would increase slightly because of the application process, where the coating is applied to the fabric.
If it proves possible to scale up the production of affordable cooling fabrics, the benefits could extend far beyond clothing, some researchers say.
Scientists at the University of Chicago hope their cooling fabric, made from materials such as silver nanowire and wool, could also be used to cool buildings and cars. In tests under the blazing Arizona sun, they found that the fabric stayed 16 degrees Fahrenheit cooler than commercial silk fabric often used in summer clothing.
The broader use of refrigerants would reduce the cost and climate impact of air conditioning, the scientists said. “Our civilization actually uses about 10 to 15 percent of the total energy to keep ourselves comfortable, wherever we go,” Po-Chun Hsu, a professor of molecular engineering at the University of Chicago and an author of the study, said in a statement.
To tackle extreme heat, the burning of fossil fuels must be rapidly reduced. But deadly heat waves are already happening, and some scientists believe these cooling substances could play a useful role as more people are exposed to heat that their bodies can’t tolerate.
“Personal cooling textiles hold great promise for addressing the heat-related impacts of climate change,” Xueping Zhang, a professor specializing in personal thermal moisture management at Donghua University in China, told CNN, who was one of the authors of the 2023 scientific review of cooling textiles.
They “can provide local cooling to specific body parts with great precision,” she added, and can be adapted to different environments.
She sees a large-scale role for cooling fabrics — and soon. “With the advancement of materials and technology, personal cooling textiles will be available (in the near future) for general public use.”
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