As materials science continues to advance, the definition of what is a solid becomes increasingly hard to pin down. Super-light aerogels have been a target of research for decades, getting less dense as new variants are developed. Now a team of researchers from China’s Zhejiang University in the Department of Polymer Science and Engineering have broken the record for the lowest density solid to date with a new type of aerogel, and they owe it to our old friend graphene.
Aerogel is usually composed of silica or carbon compounds and is highly-prized for its durability and thermal insulation properties. This family of substances is sometimes called “frozen smoke” due to its hazy appearance. In 2012 a type of aerogel composed of graphite (dubbed Aerographite) took the crown as the least dense solid at 0.18 mg/cm3. The Zhejiang University graphene aerogel edges that out with a density of just 0.16 mg/cm3.
To put those numbers in perspective, the new aerogel has a lower density than helium and only twice as much as hydrogen. Regular air, like you’re breathing right now, has a density of about 1.2 mg/cm3. That’s 7.5 times heavier than graphene aerogel. Yes, it’s less dense than air, but this near-magical substance is still a solid. A sample of graphene aerogel a few centimeters across is so light that it can be supported by delicate plants as seen above.
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