Date of Award

2026

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Electrical Engineering (PhD)

Administrative Home Department

Department of Electrical and Computer Engineering

Advisor 1

Paul L. Bergstrom

Committee Member 1

Christopher Middlebrook

Committee Member 2

Durdu Güney

Committee Member 3

Ashutosh Tiwari

Abstract

Electrochemical sensing is widely used for chemical and biological detection due to its high sensitivity, label-free operation, and compatibility with miniaturized electronic systems. However, conventional microelectrode platforms operate in an ensemble-averaged regime in which the measured current represents the collective response of many molecules interacting with the electrode surface. This ensemble averaging masks localized nanoscale electrochemical events and limits the ability to detect rare interactions, such as single molecules or nanoparticles. Achieving single-entity electrochemical detection therefore requires strategies that confine electrochemical reactions to nanoscale regions while maintaining compatibility with scalable planar microfabrication.

This dissertation investigates nanoscale electrochemical confinement on planar microelectrode arrays and establishes a framework for engineering localized electrochemical sensing platforms. The work begins with the development of planar Cr/Au microelectrodes incorporating additively manufactured nanoscale resin wells that geometrically restrict electrolyte access to submicron reaction volumes. Electrochemical measurements using ferrocyanide demonstrate significant suppression of ensemble-averaged faradaic current while preserving reversible redox behavior and diffusion-controlled transport.

To provide predictive design guidance, a finite-element modeling framework was developed to analyze ionic transport and electric-field distribution within confined electrode geometries. Parametric simulations evaluated the influence of pore radius, confinement height, and electrode spacing on diffusion-limited current and inter-electrode interactions, establishing design rules for optimizing electrochemical sensitivity while minimizing crosstalk in array configurations.

Guided by modeling insights, ultrathin  dielectric passivation was integrated onto planar microelectrode arrays to achieve electrochemical confinement through defect-mediated charge transfer. Electrochemical impedance spectroscopy and cyclic voltammetry measurements performed using the ferrocyanide redox probe show that an oxide thickness of approximately 12 nm provides effective suppression of ensemble currents while preserving localized electrochemical activity.

Finally, the nanoscale-confined sensing platform was evaluated using Cytochrome c, a biologically relevant redox-active protein. Cyclic voltammetry measurements were performed in both Cytochrome c solutions and Phosphate Buffered Saline (PBS) to compare protein and baseline electrochemical responses. Although well-defined redox peaks were not observed under the tested conditions, the experiments provided insight into protein-scale electrochemical behavior on the developed sensor platforms and confirmed stable baseline responses in PBS. Collectively, these results establish experimentally informed design considerations for nanoscale electrochemical confinement in scalable planar microelectrode arrays and provide a foundation for future electrochemical sensing technologies and single-entity detection studies.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

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