Direct Electrical Measurement of DNA Conductivity Using On-Chip Nanowire Electrodes

DNA has been one of the most popular molecules in molecular electronics. Despite the strong interest in DNA electronics, the electronic properties of the blueprint of life remain controversial and difficult to precisely determine due to the lack of a reliable single or a few molecules based electrical measurement platform and both intrinsic and extrinsic factors effecting the electron transport characteristics in DNA (Endres et al., 2004). Among a variety of electrical probing of a DNA molecule, nanometer scale separated metallic electrodes separations can be used convenient means of electrical measurement platform for molecular junctions constructed from self-assembling DNA strands (Mahapatro et al,. 2009; Iqbal et al., 2005). Here, we propose a nanowire based nanogap electronic test beds for direct electrical measurement of DNA molecular junctions. Electric-field assisted assembly of Au-Ag-Au nanowires, in which a short silver segment serves the sacrificial layer, was used to precisely align a single nanowire between a pair gold microelectrodes photolithographically defined on a Si-wafer. The sacrificial layer was selectively etched to create nanogap (100-150 nm) electrode pairs from each of the aligned nanowire. Chemisorption of thiolated DNA molecules on the surface of wire and then bridging the gap in the wire by capturing a single Au-nanoparticle (200 nm) were followed to build on-chip two DNA molecular junctions linked in series by a single gold nanoparticle (Figure 1). The nanoparticle capture was performed by AC dielectrophoresis under 10 mM pH7 histidine buffer to have low salinity and prevent the DNA monolayers on the both side of the nanowire.