Despite decades of innovation in high-tech thermal fabrics that keep marathon runners cool or keep alpine hikers warm, there has never been a material that changes its insulation properties depending on the environment. Until now.
University of Maryland researchers have created a tissue that automatically regulates the amount of heat it passes through. When the conditions are warm and humid, for example near a sweaty body, the substance passes infrared radiation (heat). As the conditions become cooler and drier, the fabric reduces the escaping heat. The development was described in the issue of February 8, 201
The researchers created the fabric from specially developed yarns coated with a conductive metal. Under hot, humid conditions, the yarn strands compress and activate the coating, altering the interaction of the fabric with the infrared radiation. They refer to the action as "gating" the infrared radiation, which acts as a tunable blind to transfer or block heat.
"This is the first technology that allows us to dynamically couple infrared radiation," said Professor YuHuang Wang of UMD's chemistry and biochemistry and one of the correspondent authors of the newspaper who led the studies.
The basic yarn for this new textile is made from fibers that consist of two different synthetic materials – one takes up water and the other repels it. The strands are coated with carbon nanotubes, a special class of lightweight conductive carbon-based metal. Because the materials in the fibers conflict with water and absorb water, the fibers warp when exposed to moisture, such as moisture. B. surrounding a sweaty body. This twist brings the yarn strands closer together, which does two things. First, the pores in the fabric are opened. This has a small cooling effect as heat can escape. Second, and most importantly, it modifies the electromagnetic coupling between the carbon nanotubes in the coating.
"You can think of this coupling effect as the bend of a radio antenna to change the wavelength or frequency with which it vibrates," Wang said. "It's a very straightforward way to think about it, but imagine you bring two antennas together to regulate the type of electromagnetic wave they absorb, and as the fibers get closer together, they interact with the radiation that Interacting with changes. Tissue interacts with the heat emanating from the human body. "
Depending on the setting, the tissue either blocks or transmits infrared radiation. The reaction is almost instantaneous. Before people realize they are getting hot, the garment could cool them down. On the other hand, as a body cools, the dynamic gate mechanism works in the opposite direction to trap it in the heat.
"The human body is a perfect cooler, it gives off heat quickly," said physics professor Min Ouyang at UMD and the other correspondent author of the newspaper. "For the entire story, the only way to regulate the cooler was by taking off your clothes or putting on your clothes, but this fabric is a true bidirectional regulator."
According to the Science paper this is the first textile that can regulate the heat exchange with the environment.
"This groundbreaking work provides an exciting new switchable feature for comfortable clothing," said Ray Baughman, professor of chemistry at the University of Texas, who was not involved in the study. Textiles have been known which increase porosity in response to perspiration or rising temperature, as well as textiles that transmit infrared radiation associated with body temperatures. However, no one had previously found a way to change both the porosity and infrared transparency of a textile "19659005] More work is needed to commercialize the fabric, but researchers say the materials used for the base fiber are readily available and the carbon coating can be easily added Standard Dyeing Process.
"I find it very exciting to be able to apply this phenomenon to the development of a textile that can enhance the functionality of clothing and other fabrics," said Ouyang.
Clothing fabric keeps you cool in the heat
X.A. Zhang et al., "Dynamic Association of Infrared Radiation in a Textile", 19459016, Science (2019). science.sciencemag.org/cgi/doi… 1126 / science.aau1217