Polar bear sweater is as warm as down jacket, but only one-fifth the thickness!

Inspired by polar bear fur, the "black technology sweater" which is thinner than traditional down jackets but equally warm, was published in the authoritative scientific journal Science today.

According to reports, the "polar bear sweater" is woven by encapsulated aerogel fibers (EAFs) made from polar bear fur by Professor Bai Hao's team at Zhejiang University. It has excellent thermal insulation, flexibility, washability and dyeability, and its thickness is only one-fifth of a down jacket with the same warmth .

The research team said such textiles have great potential in areas such as military uniforms and space suits, and are necessary for a variety of emerging applications such as wearable electronics and personal thermal management .

The relevant research paper, titled "Biomimetic, knittable aerogel fiber for thermal insulation textile", has been published in the authoritative scientific journal Science.

In a review article published at the same time, Zhang Xuetong, a researcher at the Suzhou Institute of Nano-Tech and Nano-Bionics of the Chinese Academy of Sciences, and Sheng Zhizhi, an associate researcher, wrote, "Wu et al. have found a feasible strategy to construct biomimetic weavable aerogel fibers with excellent thermal insulation and mechanical toughness, which can be made into air-permeable textile fabrics and may promote the development of advanced warm thermal textiles ."

Outperforms wool, nylon and polyester textiles

Recently, some live broadcasts selling winter clothing have been using words with a black-tech feel. Some brands have launched "aerogel cold-resistant clothing," claiming that it is thinner and lighter than down jackets and is warmer. Does aerogel really have such a good effect in keeping warm and cold-resistant?

Recently, Li Zhaoling, a researcher at the School of Textiles of Donghua University, said in an interview with the Chengdu Association for Science and Technology, "In principle, it is possible to use aerogels to keep warm, and it has good prospects for future development. At present, the mechanical properties of aerogel structural materials themselves are very poor, they are very easy to break and powder, lack flexibility and drape, and are not suitable for direct use in daily textiles and clothing."

In this study, Professor Bai Hao's team developed a polymer shell-encapsulated EAFs by imitating the core-shell structure of polar bear hair, overcoming the obstacles that have long plagued the practical application of fragile aerogels in strong insulating textiles.

The study used a simple two-step method to continuously prepare EAFs , obtaining orderly arranged porous aerogel fibers by freezing and spinning, followed by one-step coating and drying. Thermoplastic polyurethane (TPU) **** was chosen as the encapsulation layer because of its high mechanical strength and stretchability (1000% tensile strain) .

Figure｜Design and preparation of encapsulated aerogel fibers (Source: this paper)

EAFs can capture air in abundant air pockets (over 90% porosity), providing adequate thermal insulation. The thermal conductivity of sweaters made of EAFs is 26.9±1.8 mW/(m·K), which is better than wool, nylon and polyester textiles. The sweater is only one-fifth the thickness of down clothing, but has comparable thermal insulation performance and excellent washability and dyeability .

Figure | Woven and knitted aerogel textiles with excellent thermal insulation properties (Source: This paper)

However, Sheng Zhizhi said that we still face some challenges in applying aerogel fibers in real life .

For example, how to develop fast spinning technology? At present, the wet spinning rate of aerogel fibers is about 20 m/min, which is still far behind the wet spinning (200 m/min), dry spinning (1500 m/min) and melt spinning (5000 m/min) of industrial-grade traditional fibers.

In addition, how to solve the problem of the fully continuous preparation technology of spinning and drying integration? Although continuous spinning and intermittent drying have been achieved, the fully continuous preparation technology that organically combines these two processes is still difficult to become a reality. To realize the full-process continuous preparation technology of aerogel fibers, it is necessary to deeply understand the principle of rapid decompression drying and desolvation, and solve the development of continuous equipment.

However, with the development of advanced materials and the formation of advanced preparation technologies, the application of aerogel fibers is expected in the future.

Thermal insulation materials, promising future

Aerogel fiber is a promising material for the next generation of thermal insulation textiles, and great progress has been made in past research. At the same time, in addition to aerogel fibers, research on thermal insulation materials has also made continuous breakthroughs in recent years .

In February this year, a research team from the University of Science and Technology of China successfully developed an all-natural wood-like aerogel. The material uses natural biomass and natural minerals as raw materials and has excellent thermal insulation and fire resistance. It is reported that this all-natural wood-like aerogel is expected to become an ideal substitute for commercial insulation materials. In addition, its natural raw material source and low-energy and low-emission preparation process make this aerogel show good biodegradability and sustainability, which is expected to reduce the negative impact of insulation materials on the environment during production, use and disposal.

In addition, in August this year, the team of the School of Mechanical Science and Engineering of Huazhong University of Science and Technology successfully designed a thermal stealth metamaterial, which has a variety of free shapes, independent background temperature, and omnidirectional functions. These metamaterials can effectively shield the interference of external temperature fields on objects inside the device, achieve active heat insulation, and can be widely used in thermal protection of heat-sensitive components.

In general, the research in the field of thermal insulation materials has continuously produced remarkable innovative results in recent years. From aerogel fibers to all-natural wood-like aerogels, to thermal stealth metamaterials, scientists are constantly expanding the application scope and performance of materials. This series of breakthroughs not only provides people with a more comfortable and safer living experience, but also takes an important step on the road to sustainable development.

With the continuous advancement of science and technology, people's demand for thermal insulation materials will also grow. The emergence of new materials not only improves the thermal insulation effect, but also pays attention to environmental protection and sustainability, providing a feasible path for the development of green technology in the future.

We hope that these innovative materials will be used in a wider range of fields and bring more positive impacts to the sustainable development of society and people’s quality of life.

Reference Links:

www.science.org/doi/10.1126/science.adj8013

www.science.org/doi/10.1126/science.adm8388

https://www.nature.com/articles/d41586-023-04145-5

https://onlinelibrary.wiley.com/doi/10.1002/anie.202211099

https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.202302387