(147a) Influence of Mass Transfer for the Transient Response of Ultra-Microelectrodes to Potential and Current Transients

Research Interests: electrochemical engineering, corrosion science, and impedance spectroscopy; transport phenomena, energy, environment, and sustainability; modelling, theory, and simulation; Advanced materials, semi-conductor devices, and nanotechnology.

Stimulation by ultra-microelectrodes is envisioned to enable precise control for activation of the target neural population. However, the corresponding large current densities can lead to adverse effects such as tissue damage, neural degeneration, inflammation, and electrode damage. By studying the charging and faradaic reactions of ultra-microelectrodes, we can optimize stimulation parameters to minimize these risks and maximize the effectiveness of neural stimulation.

While not a direct representation of the stationary electrodes used for neural stimulation, the rotating disk geometry has the advantage of well-defined mass transfer characteristics. For the present work, a rotating disk electrode (RDE) geometry was used for mathematical modeling of electrochemical reactions at the electrode-electrolyte interface. The rotation of the disk electrode provides a uniform laminar flow of species from the bulk electrolyte to the electrode surface. The finite-element simulation of current and potential distributions on a rotating disk electrode will guide development of more specific models for neural stimulation.

We developed a finite-element model for a 2-D axisymmetric disk electrode geometry. The simulation was performed using COMSOL Multiphysics software. The radius of the electrode was 5 microns, and a fine mesh was applied to the electrode boundary to allow for accurate simulation of current density. The model accounts for the cathodic reduction of oxygen reaction on the surface of a platinum electrode and the influence of mass transfer. A conservation equation was applied to dissolved oxygen, and Laplace’s equation was used to account for variation of potential in the electrolyte. The model accounts for the concentration of dissolved oxygen and both charging and faradaic currents. The poster will show the results for stimulation protocols typical of those used for neural stimulation.