In Situ and 2D and 3D in Silico Redox Cycling Studies for Design Optimization of Coplanar Arrays of Microband Electrodes in a 70 μm × 100 μm Electroactive Footprint

Authors

Miguel Angel Abrego Tello, University of Arkansas, FayettevilleFollow
Mahsa Lotfi Marchoubeh, University of Arkansas, FayettevilleFollow
Ingrid Fritsch, University of Arkansas, FayettevilleFollow

Document Type

Article

Publication Date

6-2024

Keywords

SU-8 substrate; generation-collection; redox cycling; end and edge effects; heterogeneous electron transfer kinetics; 3D and 2D computer simulations; microband electrode arrays

Abstract

Optimization of redox-cycling currents was performed by adjusting the height (sidewalls, h), width (w), and length (l) of band electrodes and their spacing (w_gap) in coplanar arrays restricted to a small-electroactive window of 70 × 100 μm. These arrays can function in μL-volumes for chemical analysis (e.g., in-vivo dopamine detection using probes). Experiments were conducted with an array of five electrodes (NE = 5), w = 4.3 μm, w_gap = 3.7 μm, h = 0.150 μm, and l = 99.2 μm. Reasons for disparities between currents from experiments and approximate equations were determined by high-density mesh simulations and were found to arise from sluggish heterogeneous electron transfer kinetics and diffusion at electrode ends, edges, and heights. Ferricyanide, with its moderately slow kinetics, exhibits redox-cycling currents that fall below predictions by the equations as w_gap decreases and diffusional flux outpaces reaction rates. Simulations aid investigations of various array designs, achievable through conventional photolithography, by decreasing w and w_gap and increasing NE to fit within the electroactive window. A coplanar array, NE = 58, w = w_gap = 0.6 μm, h = 0.150 μm and l = 100 μm, yielded ferricyanide sensitivities of 0.266, 0.259 nA·μM−1, enhancements of 8 × and 9 × over w = w_gap = 4 μm, and projected dopamine lower limits of quantitation of 139 nM, 171 nM at generator and collector electrodes, respectively.

Citation

Abrego Tello, M. A., Lotfi Marchoubeh, M., & Fritsch, I. (2024). In Situ and 2D and 3D in Silico Redox Cycling Studies for Design Optimization of Coplanar Arrays of Microband Electrodes in a 70 μm × 100 μm Electroactive Footprint. Journal of the Electrochemical Society, 171 (6), 066512. https://doi.org/10.1149/1945-7111/ad5409

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.