Look at the tip of that old pencil in your desk drawer, and what you’ll see are layers of graphite that are thousands of atoms thick. Use the pencil to draw a line on a piece of paper, and the mark you’ll see on the page is made up of hundreds of one-atom layers.
But when UK scientists found a way — using, essentially, a piece of ordinary sticky tape — to peel off a layer of graphite that was just a single atom thick, they called the two-dimensional material graphene and, in 2010, won the Nobel Prize in physics for the discovery.
Now, researchers at the University of Delaware have conducted high-performance computer modeling to investigate a new approach for ultrafast DNA sequencing based on tiny holes, called nanopores, drilled into a sheet of graphene. Such quick and low-cost (estimated at less than $1,000) sequencing could usher in an era of personalized medicine, says Branislav Nikolic, associate professor of physics and astronomy.
“Graphene is a two-dimensional sheet of carbon atoms arranged in a honeycomb pattern,” he says. “The mechanical stability of graphene makes it possible to use an electron beam to sculpt a nanopore in a suspended sheet, as demonstrated in 2008 by Marija Drndić at the University of Pennsylvania.”
Graphene has been among the fastest-growing areas of study in nanoscience and technology over the past five years, Nikolic says, calling it a wonder material that has remarkable mechanical, electronic and optical properties.
In the new device concept proposed by Nikolic’s team, a tiny hole a few nanometers in diameter is drilled into a sheet of graphene and DNA is threaded through that nano-pore. Then, a current is used to detect the presence of different DNA bases within the nanopore. The process uses graphene nanoribbons — thin strips of graphene that are less than 10 nanometers wide and have edges made up of a specific zigzag arrangement of carbon atoms.
Nikolic says that he and postdoctoral researcher Kamal Saha used knowledge acquired from several years of theoretical and computational research on the electronic transport in graphene to increase the magnitude of the detection current in their biosensor by a thousand to a million times when compared to other recently considered devices.
Nikolic, Saha and Drndić recently published the results of the computer modeling in the journal Nano Letters, published by the American Chemical Society. Colleagues, led by Drndić at Penn, will now seek to fabricate the biosensors in their lab, guided by the simulations.
In June, in Pisa, Italy, a workshop organized by Nikolic and sponsored by the Centre Européen de Calcul Atomique et Moléculaire, brought together leading experts in computational modeling and investigation of nanodevices for third-generation DNA sequencing technologies.