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.

Now read: Harvard cracks DNA storage, crams 700 terabytes of data into a single gram

Research paper: DOI: 10.1088/0957-4484/24/27/275301 – “Direct writing on graphene ‘paper’ by manipulating electrons as ‘invisible ink.'” [Free PDF for 30 days]