We have investigated the formation and electrical properties of nanowire bridges formed when nanowires modified with the biomolecule biotin span across a gap between gold microelectrodes functionalized with the complementary biomolecule, avidin. Dielectrophoretic manipulation with a 1 MHz AC voltage is used to manipulate biotin-modified nanowires into the inter-electrode gap. Biomolecular recognition between the biotin-modified nanowires and the avidin-modified gold microelectrodes then holds the nanowires securely in place. By simultaneously applying a second, lower-frequency AC voltage and using lock-in detection, we are able to monitor individual bridging events in real time and to characterize the change in electrical response associated with individual nanowire bridges. The combined use of physical manipulation with biomolecular recognition can be used for selective assembly of nanoscale materials, as well as analytical application as a biologically activated switch in which an electrical contact is controlled by a biomolecular recognition process.
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