Electrically directed assembly and detection of nanowire bridges in aqueous media

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