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Recently, a research team led by Zipeng Chen, Qian Zhang (corresponding author, Nanjing University/Wuhan Textile University) from the National Laboratory of Solid State Microstructures at Nanjing University, and Liping Ding (Suzhou Laboratory) from Shaanxi University of Science and Technology, with contributions from researchers from the School of Engineering and Applied Sciences at Nanjing University, Jiangsu Key Laboratory of Artificial Functional Materials, State Key Laboratory of New Textile Materials and Advanced Processing at Wuhan Textile University and other institutions, published a paper titled "An infrared-transparent textile with high drawing processed Nylon 6 nanofibers" in Volume 16 of Nature Communications in 2025 (Nature Communications, 2025, 16: Article number 2009).
With the continuous growth of global energy demand, reducing energy consumption has become crucial for achieving sustainable development. Traditional air - conditioning systems consume a large amount of energy when regulating indoor temperatures. Textiles, as materials in direct contact with the human body, have great potential in personal thermal management. Infrared (IR)-transparent radiative cooling textiles have attracted much attention due to their potential in achieving personal thermal comfort and reducing energy consumption. However, most of the currently available IR - transparent textile materials are a few synthetic fibers, and traditional textile materials are difficult to achieve IR transparency, which limits their large - scale practical applications. Nylon 6 (PA6), a common textile material, is widely used for its excellent processability, strength, and stability. However, its high absorbance in the IR region makes it difficult to be directly used in IR - transparent textiles. Therefore, the development of IR - transparent textiles based on PA6 is of great significance for expanding the application fields of traditional textile materials and promoting the development of energy - saving technologies.
This study is based on PA6. By designing a process that combines high drawing treatment with rapid solvent evaporation, an IR - transparent PA6 textile (IRT - PA6) was successfully prepared. The research team significantly weakened the molecular vibrations (IR absorption) of PA6 in the IR region by changing the conformation of PA6 molecular chains and crystal structures. At the same time, the fiber size was adjusted to the nanoscale to minimize IR reflection. Experimental results show that the human body covered with this textile can be 2.1 °C cooler than when covered with cotton fabric, which is equivalent to a reduction of approximately 20% in indoor cooling energy consumption.
(1) Regulation of Molecular Structure and Crystal Structure
The research team analyzed the influence of the molecular structure and crystal structure of PA6 on its IR absorption. PA6 has two common crystal structures, the α - phase and the γ - phase. The α - phase is the most stable crystal phase, with molecular chains arranged in an antiparallel manner, and hydrogen bonds formed in the plane and collinear with the plane of the aliphatic segment. The γ - phase is a metastable phase, with molecular chains arranged in a parallel manner and hydrogen bonds formed in a different plane. Through theoretical simulations, it was found that the bond vibration intensity of the α - phase is significantly higher than that of the γ - phase, resulting in stronger absorption of α - phase PA6 in the IR region. Therefore, the research team adopted an electrospinning process with high drawing and rapid solvent evaporation to promote the ordered arrangement of PA6 molecular chains and achieve the transformation from the α - phase to the γ - phase, thereby reducing IR absorption. In this process, an electrospinning machine was used to precisely control the parameters and ensure the quality of the nanofibers.
(2) Influence of Nanofiber Structure on IR Reflection
To further improve the IR transmittance, the research team adjusted the size of PA6 fibers to the nanoscale. Theoretical calculations show that when the fiber diameter is much smaller than the IR wavelength, scattering losses can be significantly reduced, and the transmittance can be improved. In the experiment, by optimizing the electrospinning device parameters, the average diameter of PA6 fibers was controlled at about 150 nm, which is much smaller than the IR wavelength, thus minimizing the scattering loss. In contrast, fibers with a diameter of 10 μm (similar to commercial textile fibers) showed higher reflectivity.
(3) Cooling Performance of IRT - PA6 Textiles
The research team tested the cooling effect of IRT - PA6 textiles through an experimental device that simulates the human skin. The experimental results show that the temperature of the simulated skin covered with IRT - PA6 textiles is the lowest. Compared with commercial PA6 textiles and cotton fabrics, it is reduced by 2.5 °C and 3.3 °C, respectively. In addition, by directly observing the IR radiation flux through a thermal imager, it was found that when IRT - PA6 textiles first come into contact with the simulated skin, they show warm colors due to their high IR transmittance, while commercial PA6 textiles and cotton fabrics show cooler colors due to their absorption of IR radiation. After reaching a steady state, the IRT - PA6 textiles show the lightest color, indicating the lowest local temperature.
(4) Wearability and Energy - Saving Potential of IRT - PA6 Textiles
In addition to its excellent cooling performance, the IRT - PA6 textile also has good wearability. Experiments show that this textile has ideal water vapor transmission properties, supporting the penetration of water vapor generated by sweat evaporation. At the same time, its air permeability is comparable to that of cotton fabric, which benefits from its fibrous structure and micro - pores formed by laser drilling technology. In addition, the IRT - PA6 textile also shows high tensile strength and ductility, comparable to commercial cotton fabrics. By sandwiching IRT - PA6 between two layers of nylon mesh and bonding them with an adhesive, its durability can be further improved without significantly affecting its IR transmittance.
Based on the cooling advantages of IRT - PA6 textiles, the research team also analyzed their energy - saving potential. Several hot cities in China were selected, and the average energy savings during indoor cooling when wearing IRT - PA6 textiles instead of cotton fabrics were calculated under the average maximum summer temperatures in the past thirty years. The results show that when the ambient temperature is about 30 °C, about 20% energy savings can be achieved.
In summary, this study developed an infrared (IR)-transparent textile based on highly drawn Nylon 6 nanofibers. Different from commercial PA6 with high IR absorbance, this study significantly weakened the bond vibrational intensity of molecular chains and adjusted the fiber size to the nanoscale, minimizing the absorption and reflection of PA6 textiles and ultimately achieving high IR transmittance. In simulated skin tests, this IR - transparent textile is 2.5 °C and 3.3 °C lower than IR - absorbing PA6 textiles and cotton fabrics, respectively. When the human body is covered with the designed IR - transparent textile, the temperature is 2.1 °C lower than when covered with cotton fabric, indicating a reduction of approximately 20% in energy consumption during indoor cooling. This research will provide an effective way for passive cooling and inspire innovative approaches to the development of materials for reducing global energy consumption.
Article source: https://doi.org/10.1038/s41467-025-57366-9
