Scientists have just unveiled the lightest human-made substance on Earth. How light are we talking? Let's put it this way: it's less dense than helium.
The battle for rights to the title of world's lightest material (technically world's lowest density material) has played out like a brutally rapid series of monarchal overthrows. For years, NASA's aerogel (density 1 milligram per cubic centimeter) held the title of lightest material on Earth. In November 2011, it was dethroned by a gorgeous, ultralight metallic microlattice (density 0.9 mg/cm3). Months later, a substance called "Aerographite" with a density of just 0.2 mg/cm3 blew both of these ultralight materials out of the water. Now, a new material has assumed the throne.
In a Nature paper titled "Solid carbon, springy and light," scientists from Zhejiang University in Hangzhou, China have introduced a graphene aerogel that comes in at just 0.16 milligrams per cubic centimeter. As a point of reference, that's less than one-seventh the density of air. And while it's still twice as dense as hydrogen, it's the very first ultralight substance to achieve a mass-to-volume ratio less than helium's, 0.1786 mg/cm3. What's more, it's got some killer real-world applications.
PhD candidate Sun Haiyan explained, "It's somewhat like large space structures such as big stadiums, with steel bars as supports and high strength film as walls to achieve both lightness and strength. Here, carbon nanotubes are supports and graphene is the wall."
The new material is amazingly absorptive, able to suck in up to 900 times its own weight in oil at a rate of 68.8 grams per second — only oil, not water, which means it has massive potential as a cleaning material when it comes to events such as oil spills.
Then, both the graphene aerogel and the oil could be recycled.
Here's a brain-teaser for the MSE-inclined: the last several ultralight materials to hold the title of "world's lightest" have had densities less than air (1.2 mg/cm3) – so why don't any of them float? Let's hear your input in the comments!