07-Feb-17 Scientists at Stanford University have developed a material that would block the sun’s rays and also allow venting of body heat. The scientists have described the new fabric, a nano-porous form of polyethylene, and its properties in the journal Science. For now, the fabric has been tested by humans. The scientists carried out a test in which they wrapped the high-tech fabric around a device that imitated the response of human skin on a hot day. The temperature rose by mere 0.8 degrees Celsius.
In the case of the devices covered in cotton or commercially available polyethylene, the temperature rose by 3.5 degree and 2.9 degree. The new fabric is so cool that if a person would wear a shirt and hat made with it then he would feel quite good under a shady tree even during a hot day. MIT nanoengineer Svetlana V. Boriskina said that the fabric will pave the way for a new era of ‘personalized cooling’. One day, the material would find its use in the construction of tents, buildings and vehicles.
The researchers have explained that the material is able to keep warmth at bay by scattering specific wavelengths of light. Cotton fabric provides a cool-feel, but it also traps body heat inside the garment. Such is not the case with nano-porous polyethylene fabric. Majority of the heat that radiates off human body at normal skin temperature is in the infrared portion of the light spectrum. In lab tests, cotton permitted only 1.5% of the longer infrared wavelengths to pass through. The actual need is of the fabric that is transparent to infrared radiation and is opaque to wavelengths of visible light. The nano-polyethylene fabric reflected 99% of visible light. In nature, Saharan silver ants keep themselves cool this way.
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