Graduation Year

2008

Document Type

Thesis

Degree

M.S.

Degree Granting Department

Chemical Engineering

Major Professor

Shekhar Bhansali, Ph.D.

Keywords

Dielectrophoresis, Square Wave Voltammetry, BioMEMS, Electrochemistry, Thiol chemistry

Abstract

This thesis describes the theoretical modeling of a response of an electrochemical BioMEMS sensor for detecting small amounts of cortisol hormone. The electrochemical sensor utilizes a catalyst enzyme (3a-HSD) to convert cortisone to cortisol and the Square Wave Voltammetry (SWV) as a preferred method to measure the forward and reverse current of the system. The parameters and equations necessary to estimate the Square Wave Voltammetry (SWV) theoretical response are determined and outlined. The response is modeled and the results are compared to the experimental data. Further, the design of the sensor is analyzed and suggestions are made on how to improve the repeatability of the sensor's response. The diffusion coefficients for cortisone and cortisol hormone are calculated to be 2.87*10?¹° and 2.84*10?¹° square meters per second respectively with 10 percent tolerance. The dimensionless peak current (?) for the system is approximately 10 percent lower than the one theoretically postulated by Bard et al. [3]. The surface area of the working electrode of the sensor varies with and is directly proportional to the concentration of the analyte. Theoretical current peaks are hypothesized to be within 10 percent tolerance limits (mainly due to the reason that the surface area of the working electrode is itself a variable).

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