When the weather warms up, pop on cooling clothes
You might add layers when the thermostat drops, but could clothing actually help you cool off too? Stanford University researchers have found a way. Anthea Batsakis reports.
In hot weather, we can only shed so many layers of clothes before it starts to get rude – but now a low-cost material has been invented that cools you down when you start heating up.
Developed by researchers at Stanford University, the material reflects sunlight from the body while providing an escape route for heat radiating from our skin.
The fabric is a creative substitute for air conditioning or other indoor cooling devices, Po-Chun Hsu, Yi Cui and colleagues write in Science.
They hope the material can be developed on a commercial scale and have a global impact by reducing greenhouse gas emissions.
The human body emits mid-infrared radiation. But this is the core of the cooling problem – wavelengths of our infrared emissions sit so close to visible light on the electromagnetic spectrum, the two overlap a little.
This means regular clothes that block visible light from entering also trap body heat.
The cool fabric from Stanford, though, lets infrared through, lowering temperatures between 2 °C and 3 °C. It also facilitates air and water vapour flow, making things more manageable when we sweat.
It’s made of a flexible and durable version of the thin plastic film you might use in the kitchen to cover food called polyethylene.
But unlike cling film, the new material is treated with safe chemicals to create nanoporous polyethylene, which lets water evaporate through tiny pores.
Compared to pure cotton, though, the material is far more “breathable”: cotton only allows 1.5% of infrared waves to pass, while the porous polyethylene clears the way for 96% of infrared waves radiated from our skin.
Peter Musk, who also seeks to find sustainable clothing alternatives at the State Library of Queensland in Australia, says it’s important to consider the costs developing this material would have.
“This new polyethylene product may well reduce the need for energy use by the end user, but analysis of the total cost to the environment, and greenhouse gas emissions involved in mining, transporting, refining and manufacturing the product might produce a different conclusion about its contribution to sustainability,” Musk says.
In any case, instead of cranking up the air conditioning, you might one day change your clothes instead. The scientists are working on adding more colours and textures to their range over the next few months.