**Bending and twisting of encapsulated aerogel textiles are shown. **Science (2023). doi： 10.1126/science.adj8013
A team of chemical engineers and materials scientists at Zhejiang University in China has developed a new type of aerogel fiber that has proven to be warmer than down when woven into sweaters. In their first article, published in the journal Science, the group describes the inspiration for their fibers, how they are made, and how effective they are when tested in cold environments. Zhizhi Sheng and Xuetong Zhang of the Chinese Academy of Sciences published a Perspective article in the same journal outlining the work the team is doing in this new work.
Aerogel is the type of gel in which the liquid is replaced by air. They were invented in the 1930s and have been used in a variety of applications, including NASA space vehicles. Due to their positive thermal properties, materials scientists have been experimenting with using them to make fibers that can be used to make warm textiles. However, so far, such attempts have mostly failed due to lack of moisture permeability and strength. In the new study, the Chinese team found a way to overcome both problems.
The researchers' work began with mimicking the thermal properties of polar bear fur. They point out that the reason why bears are able to stay warm in such cold temperatures is because the hairs that make up their fur have both a porous core and a dense shell. To reproduce these properties, the team started with precursors, creating what they described as encapsulated aerogel fibers, which they spun while frozen. This process results in a sol-gel transition. The material is then freeze-dried and coated with a semi-hard shell.
The result is a production of fine round fibers of the desired length. The researchers noted that post-processing is not required to produce textiles, suggesting that their fibers can be cheaper than those currently used.
Next, the team produced a batch of long strands of fiber, which was used to weave sweaters. They then tested the sweater's warmth by exposing it to temperatures as low as -20°C. They claim that the sweater has better heat protection than similar sweaters made of down, wool, or cotton. They also stretched the sweater 10,000 times and found that it was barely damaged. They also point out that fibers can be stretched, dyed, and bent.
More information: Wu Mingrui et al., Biomimicry, Knittable aerogel fibers for insulating textiles, Science (2023). doi： 10.1126/science.adj8013