Japanese engineers weave fabric that can heat or cool a wearer

Textile engineers at Shinshu University in Japan have woven a fabric that can heat up or cool down depending on the outside temperature. The fabric is woven out of super-fine nano-threads that contain a special “phase-change” material (PCM) that can store and release large amounts of heat.
“This fabric can potentially be used as a personal thermal management system to help people maintain a comfortable temperature. It can also be used in non-wearable applications. For example, as an external packing component to help regulate the temperatures of electronics and batteries,” Hideaki Morikawa told over email.
Morikawa is the corresponding author of the research article published in the journal ACS Nano.

Occupations in many industries, like cold storage, baking, and others, require workers to shift between vastly different temperatures as part of their work. Apart from making their work uncomfortable, such temperature shifts can also cause workers to fall ill. One solution to this could be constantly changing clothing, which can be cumbersome. It would be very inconvenient for a cold storage worker to wear a sweater every time they go into a freezer and take it off when they exit.
This is where PCMs come in. Their ability to absorb and release heat could mean that they can absorb heat in hot conditions and release it when it gets cooler and vice versa. But these materials present their own set of problems. A t-shirt would not be very practical if it were made out of a material that would melt when you step out in the heat.
Some methods have tried to solve this problem having small “microcapsules” containing these PCMs built into various applications. But according to Morikawa, this technology offers “insufficient flexibility for any realically wearable applications.”
Because of this, Morikawa and his team turned to a different method called coaxial electrospinning. Electrospinning is a method to manufacture fibres with diameters in the order of nanometers. The research team spun a nanofiber with a PCM encapsulated at its centre. But they didn’t stop there.

They then went on to couple this PCM-encapsulated material with two other technologies: photoresponsive materials and an electrothermal conductive coating. The photoresponsive material absorbs heat from direct sunlight and the electrothermal coating converts excess heat into electricity. The fabric combines these three different technologies to expand the range of environments where it can be used.
But according to Morikawa, “there may be a long way to go before large-scale production” of this special fabric. For one, the researchers did test various configurations of the fabric in temperatures between zero to 80 degrees celsius but they did not explore how the material could deteriorate over time in various conditions.
Also, coaxial electrospinning is a complicated process that according to Morikawa has “strict requirements for spinning,” making it currently impractical outside laboratory settings. Further, the conductive polymer used in the fabric is quite expensive and the researchers will need to find a cheaper alternative in the future.