Schematic diagram of a prototypical solid-state, multilayer device containing a GNR layer (black) with a nanopore, sandwiched between two oxides (transparent) atop a heavily doped Si back gate, VG (green). The DNA is translocated through the pore, and the current is measured with the source and drain leads, VS and VD (gold). (See SI Methods for a cross-sectional schematic diagram.) Credit: Copyright © PNAS, doi:10.1073/pnas.1308885110 In the ongoing quest to devise faster, lower-cost methods for sequencing the human genome, scientists at University of Illinois at Urbana–Champaign have developed a novel approach: DNA molecules are sensed by passing them through a layer of constricted graphene embedded in a solid-state membrane containing a nanopore (a small hole with a roughly 1 nm internal diameter), located in a graphene nanoribbon (GNR). A critical feature of the new paradigm is that graphene’s electrical properties allow the layer to be tuned in several distinct ways – namely, altering the shape of its edge, carrier concentration and nanopore location – thereby modulating both electrical conductance and external charge sensitivity. The researchers found that their novel technique can detect the DNA strand’s rotational and positional conformation, and demonstrated that a graphene membrane with quantum point contact geometry exhibits greater electrical sensitivity than on with

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