(Nanowerk Spotlight) Imagine standing under an intense midday sun, with no shade in sight. The heat is unbearable, and for outdoor workers, athletes, and soldiers, such conditions can quickly lead to heat stress or even life-threatening situations. While air conditioning provides relief indoors, it’s not an option for those constantly exposed to extreme temperatures. Instead of energy-draining systems, the solution may lie in a simple yet powerful innovation: the fabric we wear.
A team of researchers at Nanjing University of Science and Technology, has developed a new kind of fabric that could keep people cool without the need for electricity. Drawing inspiration from the natural cooling mechanisms found in beetles and plants, this “metafabric” blends radiative cooling, sweat-wicking, and evaporative functions in a single material.
Described in a study in Advanced Functional Materials (“Bioinspired Metafabric with Dual‐Gradient Janus Design for Personal Radiative and Evaporative Cooling”), the fabric is designed to reflect sunlight, dissipate body heat, and efficiently manage sweat, offering a highly effective means of temperature regulation in harsh environments. As heatwaves become more frequent due to climate change, such technologies could be vital for mitigating the risks of overheating.
Radiative cooling is a process in which heat is radiated from the body in the form of infrared energy. This allows the wearer to cool down without requiring any external energy input. While promising, fabrics designed for radiative cooling alone have limitations, particularly during intense physical activity, which generates excessive heat and sweat. In these situations, existing materials are unable to keep up, requiring additional cooling mechanisms to maintain comfort and safety.
The new metafabric tackles this challenge by combining radiative cooling with sweat management, a dual approach inspired by nature. The Cyphochilus beetle, native to equatorial regions, is equipped with super-white scales that scatter sunlight, preventing it from overheating. Inside the beetle’s scales, a complex structure reflects sunlight while also radiating heat away in the form of infrared energy.
Meanwhile, plants use a different approach for cooling. Through transpiration, they transport water from their roots to their leaves, where it evaporates and cools the plant. These natural systems provided the blueprint for the design of the metafabric, which uses a dual-layer structure to manage both heat and moisture.
Design and fabrication of the bioinspired metafabric. a) Photograph of the Cyphochilus beetle. b) SEM image of the beetle’s scales. c) Crosssectional SEM image of the beetle’s scale. d) Schematic diagram of the transpiration effect of plants. e) Conceptual diagram of the bioinspiredmetafabric, showing its structure, functions, and chemical structural formula. (Image: Adapted from doi: with permission by Wiley-VCH Verlag)
The fabric’s structure is crucial to its performance. By stacking fibers to create a reflective, porous network, the metafabric achieves a remarkable solar reflectance of 99.4%, meaning it reflects nearly all sunlight, minimizing heat absorption. At the same time, the material’s mid-infrared emittance of 0.94 allows it to radiate body heat effectively, reducing skin temperature by as much as 17.8 °C under direct sunlight. This is a significant improvement compared to conventional fabrics like cotton, which offer much lower cooling performance.
But the metafabric’s true innovation lies in its sweat-wicking capabilities. The fabric’s dual-gradient Janus design consists of two layers: a hydrophilic (water-attracting) top layer that wicks sweat away from the skin, and a hydrophobic (water-repelling) bottom layer that prevents moisture from being trapped. This combination enables sweat to evaporate quickly, enhancing the cooling effect and preventing the discomfort associated with excessive sweating. In tests, the metafabric was able to cool the skin to a comfortable temperature with as little as 0.5 milliliters of sweat per hour – much less than the amount required by traditional fabrics like cotton, which tend to trap moisture and become heavy.
The researchers took the cooling function one step further by incorporating mesoporous silica nanoparticles into the fabric. These nanoparticles can absorb moisture from the air in humid environments and release it in dry, hot conditions, adding an extra layer of cooling. Known as moisture desorption, this process allows the fabric to reduce skin temperature by an additional 2.5 °C during the hottest parts of the day, when heat stress is at its peak. This dynamic cooling mechanism makes the metafabric especially effective in environments where temperatures fluctuate between night and day or in high-humidity conditions.
Field tests showed the fabric’s effectiveness: during peak sunlight, the metafabric lowered skin temperature by up to 17.8 °C compared to bare skin and by 11 °C compared to cotton fabric. Additionally, the fabric’s ability to absorb moisture at night and release it as evaporative cooling the next day ensures it continues to regulate temperature even as conditions change.
Beyond its cooling properties, the metafabric is designed for wearability. It is lightweight, breathable, and highly durable, making it practical for extended outdoor use. It also retains its performance after multiple washes and is resistant to UV radiation, essential for long-term outdoor applications. Moreover, the fabric can be produced in various colors without sacrificing its thermal properties, thanks to the use of fluorescent pigments rather than traditional dyes.
As global temperatures rise and heatwaves become more severe, the need for effective, energy-efficient personal cooling solutions is greater than ever. The metafabric offers a promising step forward, combining multiple cooling mechanisms in a single material that can operate without any external energy input. With applications ranging from outdoor workwear to military gear and athletic clothing, this fabric could protect against the risks of heat stress and improve comfort in extreme environments.
The development of this bioinspired metafabric marks an important advance in personal cooling technology. By reflecting sunlight, managing sweat efficiently, and dynamically adjusting to environmental conditions, it offers a practical and sustainable solution to the challenges of staying cool in extreme heat. As research continues, this fabric could find its way into a wide range of uses, helping people stay safe and comfortable in an increasingly hot world.
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