Aerogel is a synthetic gel whose liquid is replaced with gas. Although the gel—effectively a material—is still solid, its gaseous composition makes it extremely porous, much like an ultralight foam. Indeed, aerogel’s thermal conductivity is so low that it’s often touted as an ideal insulator. Although aerogel must be kept dry—its structure deteriorates when wet—coated panels of the material have found their way into buildings for decades.
Unfortunately, aerogel is also fragile and difficult to process, problems that have hindered its application as a knittable textile. Over the past decade, researchers have made fibers out of aerogel using graphene, carbon nanotubes, cellulose, and other ingredients to improve their mechanical properties. Yet existing aerogel fibers remain too weak and inflexible to knit into practical clothing.
Led by material scientists Weiwei Gao and Hao Bai (both with Zhejiang University in Hangzhou, China), Mingrui Wu and colleagues have overcome both problems. Inspired by the structure of polar bear fur, they developed a method for creating aerogel fibers that are strong enough to be twisted or tied into woven configurations. They first fabricated a microscopic spool of aerogel thread, or core, using a technique known as freeze-spinning and then freeze-dried the result to retain its porous structure. Next, they encapsulated the core in a dense thermoplastic shell made of polyurethane. The combination—a porous inner core and dense outer shell, as shown above—prevents heat loss and makes the fibers waterproof and mechanically strong.
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