Plastic ‘Fabric’ Cools Body Better Than Cotton

     (CN) — A plastic-based textile that can cool your body more efficiently than other natural or synthetic fabrics has been developed, offering a low-cost option to keep people cooler in poorer nations where air conditioning is a luxury.
     The fabric was created by engineers at Stanford University, who presented their work Thursday in the journal Science. It allows the body to discharge heat in two ways that would make the wearer feel nearly 4 degrees Fahrenheit cooler than if they were wearing cotton clothing.
     “If you can cool the person rather than the building where they work or live, that will save energy,” said Yi Cui, an associate professor of materials science and engineering at Sanford.
     The invention cools a person’s body by allowing perspiration to evaporate through the material, which ordinary fabrics already do. However, the Stanford material provides an additional cooling mechanism by allowing body heat emitted as infrared radiation to pass through the plastic textile.
     All objects, including our bodies, release heat in the form of infrared radiation, an invisible and harmless wavelength of light. Blankets warm us by trapping infrared heat emissions close to the body. Radiation emitted from the body is what makes humans visible in the dark through night-vision goggles.
     “Forty to 60 percent of our body heat is dissipated as infrared radiation when we are sitting in an office. But until now there has been little or no research on designing the thermal radiation characteristics of textiles,” said Shanhui Fan, a professor of electrical engineering from Stanford.
     To create their cooling textile, the team blended nanotechnology, chemistry and photonics to give polyethylene — the clear, clingy plastic we use as kitchen wrap — the ability to let thermal radiation, air and water vapor to pass through while being opaque to visible light.
     While the components presented various issues, the engineers bypassed deficiencies through a series of tweaks that included using a variant of polyethylene commonly used in battery making. The team then treated the industrial polyethylene with benign chemicals to enable water vapor molecules to evaporate through microscopic pores in the plastic.
     To test the cooling ability of their three-ply construct, the team compared their creation with a cotton fabric of comparable thickness by placing a small swatch of each material on a surface that was as warm as bare skin. They then measured how much heat each material trapped.
     “Wearing anything traps some heat and makes the skin warmer,” Fan said. “If dissipating thermal radiation were our only concern, then it would be best to wear nothing.”
     The comparison showed that the cotton fabric made the skin surface 3.6 degrees Fahrenheit warmer than the team’s cooling product, which may present enough of a cooling effect that a person would feel less inclined to turn on an air conditioner or a fan, the researchers believe.
     The team is now working on adding more colors, textures and cloth-like characteristics to their material.
     Fan believes that this research opens up new avenues to cool or heat other objects, passively, without the need for outside energy.
     “In hindsight, some of what we’ve done looks very simple, but it’s because few have really been looking at engineering the radiation characteristics of textiles,” he said.

%d bloggers like this: