Localized Electrodeposition and Patterning Using Bipolar Electrochemistry

Abstract

Microscopic, spatially controlled, and highly efficient bipolar electrochemistry can be performed on an electrically-floating macroscopic conductive substrate using a tool we call the Scanning Bipolar Cell (SBC). The operating principle for the SBC is that current follows the path of least resistance. A high ohmic potential drop can be generated in the electrolyte adjacent to the conductive substrate by using a moderate conductivity electrolyte with a microjet cell geometry, inducing localized charge transfer on the substrate beneath the microjet. The equal and opposite redox chemistry necessary for sustained bipolar electrochemistry is spread over the macroscopic far-field of the floating conductive substrate. We combine experiments and finite element simulations to demonstrate this system using reversible copper redox chemistry. Bipolar electrochemical coupling to the surface can be highly efficient in the SBC and is governed by the balance of interfacial charge transfer and solution ohmic resistances, as characterized by the Wagner number of the system.