A physical film composed of tiny carbon nanotubes (CNT) could be a key material in manufacturing clothes that heat and cool the human wearer at will, according to a recent study published in ACS Applied Energy Materials.
Carbon-nanotube film could heat, cool smart clothes
From a team of researchers at North Carolina State University, the finding shows how a CNT film contains a combination of electrical, thermal, and physical properties capable of making an exceptional candidate for the next generation of smart fabrics.
The researchers also optimized the thermal and electrical properties of this new material, which helped it retain desirable properties even while exposed to air for several weeks. Additionally, these properties were achieved via relatively simple processes that didn't require excessively high temperatures, according to phys.org.
"Many researchers are trying to develop a material that is non-toxic and inexpensive, but at the same time is efficient at heating and cooling," said co-corresponding author of the study Tushar Ghosh. "Carbon nanotubes, if used appropriately, are safe and we are using a form that happens to be inexpensive, relatively speaking. So it's potentially a more affordable thermoelectric material that could be used next to the skin."
"We want to integrate this material into the fabric itself," said the first study author Kony Chatterjee, a doctoral student at NC State. "Right now, the research into clothing that can regulate temperature focuses heavily on integrating rigid materials into fabrics, and commercial wearable thermoelectric devices on the market aren't flexible either."
Cool clothes: thermal, electrical conductivity
To chill down the wearer's experience (and not the body's temperature itself), said Chatterjee, CNTs possess properties that could help heat leave the body with an external current source.
"Think of it like a film, with cooling properties on one side of it and heating on the other," added Ghosh.
The researchers measured the material's capacity to conduct electricity, and also its ability to conduct thermal energy — or the capacity to let heat move through the material.
A big part of the study showed that the material has a low thermal conductivity — which means heat won't easily travel back to the wearer after leaving the body to cool it down. This also means the material — if used in warm weather — would actually allow heat to move in a current toward the body instead of sending it back out into the surrounding atmosphere.
Smart clothes with thermal accuracy
The research team was also able to measure the material's thermal conductivity with great accuracy via a collaboration with Jun Liu, an assistant professor of mechanical and aerospace engineering at NC State. Together, they used a unique experimental design to take more accurate measurements of the material's thermal conductivity in the direction that electric current moves throughout the material.
"You have to measure each property in the same direction to give you a reasonable estimate of the material's capabilities," said Liu, also a co-corresponding author of the study. "This was not an easy task; it was very challenging, but we developed a method to measure this, especially for thin flexible films."
With advances in materials science and aerospace engineering, the smart clothes of the future are closer now more so than ever. In a time of minimal social occasions, one can only imagine how smart clothes will reshape the world of fashion.