Bipolar electrochemistry has been used in examination of electrochemical effects under high electric fields, optically-coupled experiments, and geometries where conventionally-connected electrodes would be prohibitively complex. In macro-scale bipolar electrochemistry, the difference in electric potential between the electrode and the surrounding electrolyte provides the driving force for a chemical reaction. This research extends on previous work by examining the kinetics and underlying mechanistic behavior of nanoscale bipolar electrodeposition to create conductive filaments, which behave differently due to inherent limitations of nanoscale mass transport. Nanoscale conductive filaments, usually associated with resistive memory or memristor technology, may also be used for chemical sensing and in the creation of nano-patterned electro-optic or electronic materials. Realistic implementation of the technology requires precise knowledge of the conditions that control the formation and dissolution of filaments. A silver (Ag) conductive filament is created by electrodeposition in a nanoscale gap between two electrodes, creating an atomic-scale junction. In this work, Ag conductive filaments are formed through a polymer electrolyte using a conductive atomic force microscope (C-AFM). Statistical analysis shows that the distribution of formation times exhibits Gaussian behavior, which can be modified by changing electrical parameters, polymer electrolyte thickness, and surface functionalization. Further, Ag nanoparticles have been embedded into the polymer electrolyte film, to serve as nanoscale bipolar electrodes, and statistical analysis suggests that bipolar electrochemical processes at the Ag nanoparticles slows filament formation compared to polymer films without nanoparticles. Dissolution time distributions are lognormal, and repeated re-formation of filaments from previously formed structures is characterized by rapid re-growth. The experiments demonstrate a direct-write bipolar electrochemical deposition/dissolution strategy developed as an approach to reconfigurable, non-contact in situ wiring of nanoparticle arrays – thereby enabling applications where actively-controlled connectivity of nanoparticle arrays is used to manipulate nanoelectronic and nanophotonic behavior. With application areas ranging from massively-parallel chemical sensing arrays to non-contact tunable metamaterials, increasing the repeatability and mechanistic understanding of bipolar nanoelectrodeposition is important to advancing the use of similar technology in real-world devices.

This work was supported by a NASA Space Technology Research Fellowship NNX16AM45H and the Defense Advanced Research Projects Agency FA8650-15-C-7546.