Great! Scientists have invented a new fabric that automatically cools you down when you wear it

Summer has arrived as promised. Every corner of the city seems to be in a huge furnace, suffering from the baking high temperature. The heat phenomenon has become more and more serious, bringing great challenges to people's lives.

In such a hot season, some people use fans and air conditioners to resist the high temperature, while others choose to escape from the hot city and go to the suburbs to find a bit of coolness. So why is the suburbs cooler than the city?

When talking about the temperature difference between cities and suburbs, we have to talk about the "heat island effect".

The heat island effect refers to the phenomenon that the temperature of a region is higher than that of the surrounding areas. This phenomenon forms a high-temperature area similar to an isolated island on the weather map, hence the name "heat island". The heat island effect usually occurs in cities, so it is also called the urban heat island effect.

Heat island effect. Image from the Internet

Residents of the city

How to effectively deal with the urban heat island effect

Improve the comfort of life

On June 14, 2024, scientists published an article in the journal Science about a new type of radiative cooling fabric, which is expected to improve people's physical comfort in hot weather and reduce the impact of the urban heat island effect on the human body.

The research results were published in Science magazine (Image source: Science magazine)

This radiative cooling fabric

How to cool down

The mid-infrared spectroscopy selective layered textile (SSHF) prepared by the researchers consists of three layers: a polymethylpentene (PMP) nano-micron hybrid fiber layer, a silver nanowire (AgNWs) layer, and a wool fabric layer.

Among them, the surface polymethylpentene (PMP) nano-micron hybrid fiber layer has a wide size distribution and unique chemical bonds, which can achieve high absorption rate within the atmospheric transmission window (ATW) spectral range. The atmospheric transmission window (ATM) refers to the wavelength range with strong transmission ability of solar radiation when passing through the atmosphere. This part of light can directly reach the surface and has a great effect on the increase of surface temperature.

The silver nanowire layer in the middle has high reflectivity in the entire mid-infrared region, which can effectively prevent infrared rays from urban infrastructure from being transmitted to the human body and reduce the impact of thermal radiation from urban infrastructure on the human body.

The wool fabric at the bottom can absorb thermal radiation from human skin through the air gap between the textile and the skin, and further conduct the heat to the PMP fabric on the top through the silver nanowire layer, thereby transferring heat from the human body surface to the atmosphere to achieve a cooling effect.

Structure and wearability of mid-infrared spectrally selectively layered textiles a. Structure of textiles; b. Schematic diagram of radiative heat transfer of textiles in outdoor environments; c. Mid-infrared emissivity of different materials; d. Effect of wool fabric on human thermal radiation absorption; ei. Wearable research results (Image source: Reference 1)

Experimental results show that the mid-infrared spectral selective layered textile (SSHF) prepared in this study can significantly reduce the temperature by about 6.2°C at a peak solar intensity of 1010 W/m², which is attributed to the textile's ability to effectively release heat to the outside while selectively blocking thermal radiation from the ground. In experiments simulating urban environments, the mid-infrared spectral selective layered textile (SSHF) was 2.3°C and 0.2°C lower than traditionally designed radiation cooling products during the day and night, respectively.

The porous structure of the cooling textile can also provide good air permeability, promote the natural diffusion of human sweat, and avoid the discomfort caused by stuffiness. In addition, the cooling textile exhibits strong hydrophobicity and strong mechanical properties, ensuring self-cleanliness while achieving high durability, meeting the requirements of wearable clothing.

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Wearable radiative cooling products provide an innovative and effective personal cooling solution to combat the urban heat island effect, which not only helps reduce the use of air conditioning and energy consumption, but also prevents heat-related health problems. We look forward to the mass production of this high-tech product, which will bring a comfortable experience to urban residents and a cool feeling to workers working in high temperatures.

References

[1]Ronghui Wu et al., Spectrally engineered textile for radiative cooling against urban heat islands[J].Science, 2024.

[2]Cui C et al., Hierarchical-porous coating coupled with textile for passive daytime radiative cooling and self-cleaning[J].Solar Energy Materials and Solar Cells, 2022.

[3] Bai Yang, Wang Xiaoyun, Jiang Haimei, et al. Research progress on urban heat island effect[J]. Journal of Meteorology and Environment, 2013.

[4] Lu Jinghua, Li Guoping. Analysis of urban heat island effect[J]. Journal of Chengdu Meteorological College, 1991.

Planning and production

Produced by Science Popularization China

Author: Shi Chang, PhD in Physical Chemistry

Producer丨China Science Expo

Editor: Yang Yaping

Proofread by Xu Lai and Lin Lin