Dielectrophoretic Manipulation and Real-Time Electrical Detection of Single-Nanowire Bridges in Aqueous Saline Solutions

Graphical Abstract

Bridging the gap: The use of dielectrophoretic manipulation to form nanowire bridges (see picture) in saline media is demonstrated. By using nulling methods, digital-like changes in impedance can be detected that arise from the bridging and unbridging of individual nanowires in solution. This work provides a pathway for the assembly of bioelectronic switches and related devices.

Abstract

Dielectrophoretic manipulation of nanoscale materials is typically performed in nonionic, highly insulating solvents. However, biomolecular recognition processes, such as DNA hybridization and protein binding, typically operate in highly conducting, aqueous saline solutions. Here, we report investigations of the manipulation and real-time detection of individual nanowires bridging microelectrode gaps in saline solutions. Measurements of the electrode impedance versus frequency show a crossover in behavior at a critical frequency that is dependent on the ionic strength. We demonstrate that by operating above this critical frequency, it is possible to use dielectrophoresis to manipulate nanowires across electrode gaps in saline solutions. By using electrical ground planes and nulling schemes to reduce the background currents, we further demonstrate the ability to electrically detect bridging and unbridging events of individual nanowires in saline solutions. The ability to both manipulate and detect bridging events with electrical signals provides a pathway toward automated assembly of nanoscale devices that incorporate biomolecular recognition elements.