Electrically directed assembly and detection of nanowire bridges in aqueous media

Abstract

Although dielectrophoresis has been used previously to manipulate a variety ofnanoscale materials, manipulation in ionic solutions is more difficult due to thehigh dielectric constant of water and the formation of electrical double-layers.Here, we report experiments aimed at the manipulation of nanowires in aqueousmedia and real-time detection of nanowire bridging events. Real-time video imagesdemonstrate the ability to manipulate individual nanowires in aqueous mediaby capturing them along the edges of electrodes, and using a slow fluid flow totransport them until they bridge across micron-sized electrode gaps. By usingspecial cancellation schemes, we demonstrate that it is possible to eliminate theeffects of background currents through the electrolyte, and to electrically detectthe bridging of electrodes by individual nanowires and nanowire bundles. Theseresults have been obtained using gold nanowires with diameters ranging from∼50 to 250 nm,∼50 nm diameter siliconnanowires, and ∼70 nm diameter carbon nanofibres.