06 Oct 2016 |
World innovation news |
Materials & Manufacturing
nanoPE: a Significant Breakthrough in Cooling Garments!
Humans were quick to create clothing based on materials such as animal fur, synthetic fiber, or even silk to keep warm. These materials are characterized by a very low thermal conductivity which helps maintain body heat. However, designing cooling garments for hot climates remains a challenge for textile manufacturers!
The temperature of the human skin is approximately 34 °C and emits heat as infrared radiation with a portion emitting wavelengths that are present in the visible spectrum of light.
Consequently, clothing that covers the skin traps infrared radiation and prevents dissipation of the generated heat. Therefore, a solution would be to create a new material that can block visible light while filtering infrared radiation.
To this end, Po-Chun Hsu and colleagues from the Yi Cui laboratory of Stanford University studied the characteristics of a nanotextile, nano-polyethylene (nanoPE), in an article published in Science magazine.
Polyethylene is a synthetic polymer found in many everyday products such as plastic bags, sports equipment (skis, snowboards, surfboards, kites, etc.), surgical implants, or food additives. nanoPE has interconnected pores measuring 50 to 1000 nanometers in diameter, similar in size to the wavelength of visible light (Figure 1).
Light is therefore reflected and does not pass through the fabric, making the nanoPE fibres opaque.
Regarding the filtering of infrared radiation, Po-Chun Hsu and his team measured the percentage of heat flowing from the body outwards using photonic techniques. A comparative study with cotton shows that the pores of nanoPE let in 96% of infrared radiation, as opposed to 1.5% for the cotton fabric.
Ordinary polyethylene shares the same thermal characteristic, but nanoPE is 5 times more opaque, which clearly singles it out for textile production.
The researchers tested nanoPE with a device mimicking heat production in human skin, and found that it increased skin temperature by only 0.8 °C, compared to 3.5 °C for cotton and 2.9 °C for polyethylene fabrics available commercially.
In relation to these findings, Svetlana Boriskina, research assistant at MIT, confirmed that this new material could reduce energy costs associated with maintaining cooler body temperatures, and could even be used in the thermal management of tents, buildings, and vehicles.
Anouer Kebir is currently working toward the PhD degree in electrical engineering at ÉTS. His research interests include real-time optimization and control of solar energy and bioenergy.
Program : Electrical Engineering
Research laboratories : GREPCI – Power Electronics and Industrial Control Research Group