New Fabric Cools and Heats Wearer

I think everyone has hesitated before leaving their home wondering if an extra layer of clothes will be needed, even for short journeys. I know I normally check the weather before departing just for that purpose. Other people have it much worse. They may work in hot or cold workplaces, or have regular transitions between an area that is at a temperature extremity and normal temperatures. These workers could be firemen, bakers or even work in cold storage with industrial freezers. Such regular temperature transitions can even cause illnesses. However, things could be about to change as textile researchers have produced a fabric that can respond to changes in temperatures and cool wearers down or heat them up to the required temperature.

The research group, from Shinshu University in Japan, developed a new textile comprised of nano-scale threads that have a core of phase-change materials, which are able to store and release heat when they change from liquid to solid. The nano-scale threads are then combined with electrothermal and photothermal coatings to enhance the effect. The resulting material is able to get hotter or colder as temperatures change. There are several phase-change materials that can be commonly found. One example is paraffin, which reaches its melting point by absorbing heat from the environment and turns to liquid from solid. That heat is released as the paraffin comes back down to its melting point. The main drawback into incorporating these materials into clothing is that they normally are rigid in their solid form and leak when in their liquid one. Microencapsulation is one technique that has been used to try solve this problem. It involves encapsulating the phase-change materials in capsules, but this has proven quite expensive.

Instead, the researchers have used a method called coaxial electrospinning for the new material. Electrospinning is a way of manufacturing extremely fine fibers that have diameters in the order of nanometres using an electric charge to produce an extremely fine jet of liquid that solidifies and can be wound on to a drum. Coaxial electrospinning is similar, but involves two or more polymer solutions to produce a similar structure to a standard coaxial cable. The researchers encapsulated the phase-change materials in the centre of the electrospun nanofibre to stop PCM leakage. The ultra-fine fibres are flexible enough to be used in clothing clothing. To increase the thermal effect, the researchers paired the PCM material with two other personal thermal regulation technologies - photoresponsive materials that react to the sunlight, and polymers that convert electricity into heat to compensate for areas where there is little or no sunlight.

The research group is now working to improve the phase-transition properties of the fabric, and develop practical, wearable applications for the material.