Researchers from Zhejiang University and Westlake University in China have developed an environment-friendly passive nanostructured textiles that gather energy from sunlight and outer space for optional local heating and cooling. Compared with traditional heating/cooling textiles, such as black/white cotton, the new heating/cooling mode can increase/decrease the temperature of the skin simulator by 8.1°C/6°C respectively under direct sunlight. At the same time, the temperature gradient generated between the textile and the human skin allows the use of thermoelectric modules for generating electricity continuously. A square piece of fabric emits body heat or reflects solar heat when it leans against an ordinary cotton T-shirt, depending on which side faces outward.

The multilayer "Janus Textile" developed by scientists from Zhejiang University and Westlake University is composed of ePTFE (Expanded Polytetrafluoroethylene) fibers. Other substances have been bonded to these fibers, keeping one side of the fabric warm and the other cool.

Wearing clothes made of this material with the warm side facing outwards, the zinc and copper nanoparticles on that side will absorb solar energy and reduce the body heat emitted. Once the user turns the garment from the inside to outside, the porous coating of PMMA (Polymethylmethacrylate) polymer now reflects sunlight on the outer cooling side and helps dissipate body heat.

In tests conducted in natural sunlight, the temperature of the underlying simulated skin on the heated side was increased by 14°F, which is 14°F higher than black cotton. When the fabric was turned over, the skin temperature on the cooling side was reduced by 11°F compared with white cotton. When tested at night, the cooling side had no effect, although it has been proved that the heating side was 5°F warmer than black cotton.

According to scientists, the fabric has the characteristics of easy manufacture and low cost, and its air permeability is similar to that of cotton. In addition, by connecting a thermoelectric generator to the material, the researchers found that the temperature difference between the inner surface of the fabric and the skin can be used to generate a small amount of electrical energy. This function could be used to power wearable electronic devices in the future.

Source: 3xmaker