In recent years, solid-state nanopore sensing technology has attracted much attention because it shows great promise for applications in biomolecule sensing and ultrafast DNA sequencing. Graphene membranes might be used as viable sequencing platforms since the thickness of a graphene layer is comparable to the spacing between nucleotides in single–stranded DNA. Several challenges, like membrane fluctuations, pinhole defects and higher noise levels in single/bilayer graphene nanopores do not allow for the direct measurement of individual nucleotides using ionic current. The reduction of 1/f noise in graphene base devices is considered to be the biggest challenge and several research groups have tried to rectify this issue by depositing thick dielectric layers (such as Al2O3, TiO2 and HfO2) over graphene membranes. However, the deposition of dielectric layers on graphene increases sensing zone thickness and requires additional processing that deteriorates measurement reproducibility.

A team led by Prof. Ki-Bum Kim at Seoul National University has now come up with a new approach to tackle noise issues. First, the researchers replace conventionally used silicon substrates, which are the main source of dielectric noise, by quartz-based ones. Second, they utilize few layer graphene instead of single/bilayer or dielectric material coated graphene.

The first approach reduces noise levels down to 2.3 pA, which is almost six times lower than that possible with silicon-based graphene devices. Using few-layer graphene instead of single-layer or dielectric layer coated graphene also simplifies the fabrication steps and allows for identical pore sizes during the pore drilling stages.

A comprehensive noise study reveals that few layer graphene transferred onto quartz substrates possesses low noise levels and higher signal-to-noise ratios as compared to single-layer graphene without deteriorating spatial resolution. The findings imply that few layer graphene based nanopores could well lead to exciting opportunities for futuristic single-molecule genomic screening devices.

More information can be found in the journal Nanotechnology (in press).

Further reading

Simple pulling process creates nanopore for single-molecule sensing (Apr 2011)
Probing an individual DNA molecule thousands of times with a nanopore (Oct 2013)
Enhanced model describes conductance and DNA blockade of nanopores (Jul 2011)
Nanopores could unravel RNA (Jan 2010)
Nanopores sequence DNA (Oct 2009)