You can now 3D print the world’s lightest material – graphene aerogel
It’s 7.5 times lighter than air, and a cubic metre of the stuff weighs just 160 grams. It’s 12 percent lighter than the second lightest material in the world – aerographite – and you can balance a few cubic centimetres of the stuff on a dandelion head. Water is about 1,000 times as dense.
Yep, graphene aerogel is about as cool as it gets. And while silica aerogel (pictured above) is the most commonly used and studied type of aerogel, as of 2013, graphene aerogel has held the record of being the lightest material on Earth. And producing it is about to get a whole lot easier, because scientists have just figured out how to 3D print it.
Nicknamed ‘frozen smoke’, aerogel looks like a gas – and certainly has the weight and density of a gas – but is actually a solid, and an incredibly flexible, conductive, compressible, and absorbent one at that.
Its strange and entirely unique properties have scientists exploring its potential in everything from invisibility cloaks to environmental clean-up – just 1 gram of aerogel can absorb up to 900 times its own weight in materials such as oil – so a cheap, efficient way of producing it is key to accelerating the process.
Now, scientists from the State University of New York and Kansas State University describe how they’ve managed to produce it using a 3D printing technique that ensures that the whole process is automated, and every piece comes out uniform and perfect.
On its own, graphene is a two-dimensional, one-atom-thick layer of pure carbon atoms, tightly packed together in a hexagonal honeycomb lattice. To produce graphene aerogel, you basically have to freeze-dry layers of graphene and stack them into a three-dimensional structure.
Figuring out how to marry graphene aerogel with 3D printing technology was no small feat, because the molecular structure that gives rise to all its incredible properties is the one thing that makes printing it extremely difficult.
Akshat Rathi explains at Quartz:
“Typically, to 3D print aerogel, the core material is mixed with other ingredients, such as a polymer, so that it can be pushed out using inkjet printers. Once the structure is made, the polymer is removed by a chemical process. In the case of graphene aerogel, however, doing this destroys its delicate structure.”
The solution? Graphene oxide – a form of graphene with molecular oxygen incorporated into it. By mixing this compound with water and laying it out over a surface cooled to -25°C, the researchers could instantaneously freeze individual layers of graphene, and construct the three-dimensional aerogel, scaffolded by ice.
As Rathi explains, once the construction process was complete, the ice ‘scaffolds’ were removed by using liquid nitrogen to freeze-dry the water right out of the ice without damaging the rest of the structure.
“The material was then heated to remove oxygen atoms, which left only graphene in the aerogel,” says Rathi. “The resulting solid had densities ranging from 0.5 kg per cubic metre to 10 kg per cubic metre. The lightest aerogel ever produced is about 0.16 kg per cubic metre (compared to 1,000 kg per cubic metre for water).”