Scientists create nanoscopic data storage using graphene ‘paper’ and electron ‘ink’

Scientists create nanoscopic data storage using graphene ‘paper’ and electron ‘ink’.

Using graphene “paper” and electron “ink,” Danish and Chinese scientists have created one of the tiniest data storage methods ever devised. In the photo above, captured by a scanning transmission electron microscope (STEM), the thickness of the lines — the font size if you will — is just 2-3nm, or about 50,000 times thinner than a human hair. This technique could eventually be used as a means of nanoscale data storage (can you imagine storing the entire Library of Congress on a single gram of graphene?), or to create graphene-based computer circuits.

As you’re probably aware by now, graphene naturally forms into sheets that are just one atom thick. Gaphene, by virtue of being constructed out of carbon atoms, which are rather small, is the world’s thinnest known material. Interacting with a sheet material that is just one atom thick, however, is rather hard; or, in writing terms, it’s hard to find a suitable “ink.” You can use self-assembly (bottom-up), which uses external factors to control exactly where the graphene grows, but it’s very hard to do this repeatedly at an atomic scale without errors. The other option is lithography (top-down), where you start with a sheet of graphene and burn/etch away the pieces that you don’t need — but to do this, you need to focus an energy source, and there are some pesky laws of physics that get in the way when you approach atomic scales. (See: Graphene aerogel is seven times lighter than air, can balance on a blade of grass.)

The solution, according to researchers at the Technical University of Denmark in Roskilde and Tsinghua University in Beijing, is to combine both the top-down and bottom-up approaches. To do this, the researchers first fire high-energy electrons (300 kiloelectron volts) at a sheet of graphene using a scanning transmission electron microscope (STEM), which has a tip that’s just one nanometer in diameter. These electrons have enough energy to break the carbon-carbon bonds, kicking off carbon atoms and leaving dangling bonds. These loose carbon atoms then rejoin in a messy fashion, creating a region of amorphous carbon that looks very different from the surrounding graphene. By drawing lines, letters, and shapes with the STEM, the researchers leave behind a trail of amorphous carbon — which is what you see in the image at the top of the story.

According to the researchers, this technique offers both high resolution and good controllability/repeatability, which in turn could lead to nanoscale writing being used in nanoscopic data storage and electronics. The big problem, of course, is that a STEM is a room-sized piece of equipment — and, at least for the time being, we’re unlikely to invent a small, cheap device that brings graphene paper and electron ink to the mass market. That’s why the hard drive is still top of the heap when it comes to mass storage: The magnetic grains on a hard drive platter might be 50nm across, rather than the 2nm of graphene paper and ink, but a hard drive performs millions of read/write operations per minute — and it’s smaller than a deck of cards. It will be a long time until anything comes close to supplanting the hard drive.

Graphene aerogel is seven times lighter than air, can balance on a blade of grass

Chinese material scientists have created the world’s lightest material: A graphene aerogel that is seven times lighter than air, and 12% lighter than the previous record holder (aerographite). A cubic centimeter of the graphene aerogel weighs just 0.16 milligrams — or, if you’re having a problem conceptualizing that, a cubic meter weighs just 160 grams (5.6 ounces). The graphene aerogel is so light that an cube inch of the stuff can be balanced on a blade of grass, the stamen of a flower, or the fluffy seed head of a dandelion (see pictures below).

Most aerogels are produced using a sol-gel process, where a gel is dehydrated until only the aerogel remains. Some aerogels are also produced using the template  method — aerographite, for example, is created by growing carbon on a lattice (template) of zinc oxide crystals — and then the zinc oxide is removed in an oven, leaving just the carbon aerogel. To create the graphene aerogel, however, researchers at Zhejiang University use a novel freeze-drying method. Basically, it seems like the researchers  create a solution of graphene and carbon nanotubes, pour it into a mold, and then freeze dry it. Freeze drying dehydrates the solution, leaving single-atom-thick layers of graphene, supported by carbon nanotubes. The researchers say that there’s no limit to the size of the container: You could make a mini graphene aerogel using this process, or a meter-cubed aerogel if you wish.

Graphene aerogel, propped up on the stamen of a flower. The cube, which is roughly an inch across, probably weighs less than 5 milligrams.

The end result is an aerogel that weighs just 0.16 milligrams per cubic centimeter, and has truly superb elasticity and absorption. The graphene aerogel can recover completely after more than 90% compression, and absorb up to 900 times its own weight in oil, at a rate of 68.8 grams per second. With these two features combined, lead researcher Gao Chao hopes that the material might be used to mop up oil spills, squeezed to reclaim the oil, and then thrown back in the ocean to mop up more oil. Beyond filtration, graphene aerogel might be used as insulation — or, if it’s as conductive as aerographite (which seems likely), graphene aerogel could enable the creation of lighter, higher-energy-density batteries.

Over the next few pages we’ve compiled some amazing photos of aerogels. Click through if you want to see lumps of carbon balancing on a blade of grass, centimeter-thick slabs of aerogel that can insulate against the blue flame of a Bunsen burner,  or a two-gram piece of aerogel that can hold up a 2.5-kilogram brick