Nanotechnology: Holes with an edge

Tiny holes have been drilled through individual layers of graphene — atomically thin sheets of carbon — using an electron beam. These nanopores might be useful for the ultrarapid sequencing of single DNA molecules. Atomically thin layers of graphite — known as graphene — are highly electronically conducting across the plane of the material. Now researchers from Harvard University and the Massachusetts Institute of Technology show that, when used as a membrane separating two liquid reservoirs, graphene is strongly ionically insulating, while its in-plane electronic properties are strongly dependent on the inter-facial environment. The membrane prevents ions and water from flowing through it, but can attract various ions and other molecules to its two atomically close surfaces. A variety of analytical applications may result. For instance, the authors show that by drilling pores a few nanometres in diameter into these 'trans-electrode' membranes, it is possible to thread a long DNA molecule through the graphene nanopore. The DNA blocks the flow of ions, resulting in a characteristic electrical signal reflecting the size and conformation of the molecule. Such a system has potential as the basis of devices that could significantly reduce the cost of DNA sequencing.