A team of Chinese researchers announces that they have designed a meta-tissue capable of reflecting enough solar heat to lower the temperature of the human body by approximately 4.8°C . Details of the study are published in the journal Science.
Three years ago, a study pointed out that without a drastic reduction in our GHG emissions, no less than 75% of humanity could be victims of terrible and deadly heat waves at the end of the century. The results of a study recently published in the journal Climate and Atmospheric Science also indicate that maximum temperatures could reach values above 56°C, or even exceed 60°C in certain highly urbanized localities in North and Middle Africa. -Orient.
In short, you will have understood that it will get hotter and hotter over the next few decades. While efforts must therefore be made to tackle the source of global warming (human-caused greenhouse gas emissions), researchers are also working on ways to better cope with these extreme temperatures .
In this sense, a Chinese team has recently developed a new material that reflects more sunlight with the potential to keep the human body cool during strong heat waves.
This fabric consists of composite nanoparticles of titanium oxide and polylactic acid laminated with a thin layer of polytetrafluoroethylene (PTFE). The goal is to reflect as much light as possible (visible, mid-infrared and ultraviolet ranges). On paper, reflecting a large portion of these wavelengths should also allow heat to be reflected before it has a chance to be absorbed.
For this study, the researchers measured the temperature of their fabric under clear sky conditions in Guangzhou, China. They then compared this temperature to that of other common materials laid on a panel. “Under the peak of solar radiation between 11:00 a.m. and 3:00 p.m., the temperature of the meta-tissue was approximately 5.0°, 6.8°, 7.0°, 5.8°, and 10.2 respectively. °C lower to that of cotton, spandex, chiffon, linen, and bare skin simulators" , explain the researchers.
In another test, a volunteer lay down in direct sunlight for an hour while wearing a special vest made from the meta-fabric on one side and a commercial cotton fabric on the other. During this time, a thermal camera was responsible for measuring the temperature differences between the two fabrics. After one hour, the difference was 3°C . Thermal sensors placed under the fabrics also highlighted a more pronounced difference:about 4.8°C cooler for the meta-tissue .
For the researchers, this meta-fabric thus presents "efficient radiative cooling performance while offering the necessary breathability and wearing comfort “.
The team also argues that this material is compatible with commercial sewing techniques and has mechanical properties comparable to commercial fabrics (durability and water resistance). It would also be inexpensive to produce, about 10% more expensive than typical clothing fabrics .
It should be emphasized, however, that these results were for fixed subjects and objects only. It is also unknown how this material might behave with the addition of dyes. These could indeed affect its ability to reflect light. Further research will therefore still be needed, but this approach seems very promising.
