Clothes sewn from fabrics made of porous material will cool the wearer's body and reduce the need for air conditioning
As the temperature in the world rises, people use air conditioning more, but cooling the air consumes energy, the production of which involves the emission of greenhouse gases. In the US, air conditioners are responsible for emitting into the atmosphere more than 100 million tons of carbon dioxide per year.
Yai Choi, a professor of materials science and engineering at Stanford University, wants to use clothes instead of air conditioners to cool people's bodies. Even light clothes made of cotton fabric absorb the infrared radiation emitted by our bodies and in this way trap heat. Choi and his team discovered that polyethylene with nanometer holes (called nanoPE), and is also found inLithium-ion batteries, allows this radiation to escape through him. Unlike the sophisticated sportswear whose cooling mechanism depends on sweat, nanoPE fabrics will not need sweat to work.
NanoPE fabrics, whose price is similar to that of cotton fabrics, come as thin sheets meshed with holes with a diameter of 50 to 1,000 nanometers. Holes of this size allow infrared radiation to pass through the fabric, but scatter visible light, so the fabric does not appear transparent. (Normal polyethylene is a transparent material, which is obviously a disadvantage in a material intended to be used for clothing.) A sheet of nanoPE looks like a piece of thin plastic bag and tends to tear easily and not like a material suitable for sewing clothes. But Choi's team found a way to make it more suitable for the textile industry. They coated it with a water-repellent material, placed cotton mesh between two layers of nanoPE, and poked small holes in the fabric with a tiny needle to allow air to flow through it more easily. Choi found that after these actions, the fabric was able to cool a model of human skin two degrees Celsius more than cotton fabrics did. the group reported her findings In September 2016 in the journal Science.
"If you wear nanoPE, as long as the outside temperature is lower than the body temperature, you feel cool," says Choi. On hot days we may still want to use air conditioning, but we can set the thermostat to a higher temperature, and studies have shown that setting the thermostat to a higher temperature, even by a few degrees, can save almost half of the energy consumption.
The team still needs to test the nanoPE fabrics' durability, comfort and degree of cooling on real human skin. They must also understand how colorants will affect its performance. If the material passes these tests, Choi believes that in the future it will be made into uniforms and work clothes for people who work in factories and hospitals.