Single-molecule identification via tunneling currents

The National Institutes of Health (NIH) has launched the $1000 genome sequencing project towards practical realization of an ultrafast, label-free, and low-cost DNA sequencer for personalized medicine. The targeted device structure configures a pair of nanoelectrodes embedded in a nanopore. It has been proposed theoretically that reading the transverse tunneling current across a single DNA molecule with the embedded electrodes while it passes through the nanopore enables direct sequence read-out. This new detection paradigm will revolutionize the present DNA sequencing capability; full human genome sequencing, formidable task to achieve by conventional PCR-based techniques, is estimated to be completed within a few hours. Despite the huge potential, however, it lacks experimental verifications. Here, we report direct current measurements through single nucleotide molecules residing in a pair of nanoelectrodes using our configurable nanogap electrodes. We find linear current-voltage characteristics suggestive of electron tunneling transport in electrode-(single nucleotide)-electrode systems. In addition, we obtain translocation duration of single nucleotide through the electrode nanogap of about 3 ms on average, thereby proving the outstanding DNA sequencing speed capable of realizing entire human genome read-off within 3 hours via parallel operations of 1000 nanopores. We also demonstrate statistical identifications of single nucleotides via the HOMO-LUMO gap related tunneling currents, and thus providing essential scientific basis for the emerging DNA sequencing technology.

Nature Nanotechnology 5 (2010) 286-290.

Fig. Illustration of single-molecule identification via tunneling currents between nanoelectrodes.