The combination of polymers with nanopores has been of interest recently in many areas, from polymer-hybrid nanotube materials to functionalized membranes. Tightly-controlled nanopore arrays fabricated via Focused-Ion Beam (FIB) have demonstrated advantages in isolating small numbers of molecules or nanoscale objects, as with single molecule electrochemistry, and are well-suited to further engineering including multiple electrode rings and advanced surface functionalization techniques.

In this work, we discuss the ability of nanopore arrays to create ordered polymer cylinder arrays for testing the formation of nanofilaments in constrained polymer conditions as well as bipolar electrodeposition using nanoparticles. Previous work examined the kinetics of nanoscale bipolar electrodeposition by creating conductive filaments through a single nanoparticle, which demonstrated unique behavior due to the inherent limitations of nanoscale mass transport. Bipolar electrochemistry has demonstrated advantages in examining electrochemical effects under high electric fields, optically-coupled experiments, and other 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, such as the deposition of a metal ion from solution onto a surface. If that deposition is suitably controlled, a conductive filament may be created by electrodeposition, for example, in a nanoscale gap between two electrodes to create an atomic-scale junction.

This work examines the connection of multiple nanoparticles constrained in a nanopore array via the creation of conductive filaments, and the resultant change in optical behavior due to modified nanoparticle plasmonics. Preliminary theory suggests that the optical permittivity of the nanoparticle array may be tuned via formation and dissolution of the filaments. With application areas ranging from massively-parallel chemical sensing arrays to non-contact tunable metamaterials, this work uses advanced nanopore arrays to further the mechanistic understanding of nanoelectrodeposition and explore the unique challenges involved, both aspects vital to advancing the use of similar technology in real-world devices.

Special thanks to the Defense Advanced Research Projects Agency (DARPA) FA8650-15-C-7546 and the NASA Space Technology Research Fellowship (NSTRF) NNX16AM45H for providing funding for this research.