Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Electrical Engineering and Computer Science

First Advisor

Hyeun Joong Yoon


A simple, cost-effective, microfluidic, field-deployable biosensor with screen printed carbon electrode (SPCE) was developed for detection of sweat cortisol with point of care applications. Cortisol detection in artificial sweat is an important screening tool for diagnosis and monitoring of various health conditions like Addison’s disease, stress disorder, and Cushing’s syndrome. A self-assembled monolayer of graphene oxide (GO) is functionalized on SPCE electrode, onto which cortisol antibodies are immobilized for cortisol detection. Microfluidic system ensured precise and controlled flow of reagents and antibodies. Electrochemical measurement is done using cyclic voltammetry, as a function of cortisol concentrations. Cyclic voltammetry measurement gives current magnitude with applied voltage as a function of time. Scanning Electron Microscopy (SEM) imaging shows the change in surface morphology with the addition of antibody, compared to bare electrode functionalized with GO. The images confirm the antibody binding to selfassembled GO nanosurface on the working electrode. Raman imaging also supports the advantages of surface functionalization with antibodies. It shows presence of GO and antibodies on the biosensor surface suggesting GO self-assembly and antibodies immobilization. Atomic Force Microscopy (AFM) imaging shows surface topography of the developed sensor upon immobilization of self-assembled GO. The evenly distributed GO provided more surface area for antibodies immobilization. Cortisol was detected in the linear range of 0.1 ng/ml to 150 ng/ml, where current magnitude decreased with increasing cortisol concentration due to reduction in number of free electrons. The developed microfluidic biosensor for cortisol detection formed the base for sweat cortisol sensor with POC applications, and can also be used in personalized health diagnosis or monitoring.

Library of Congress Subject Headings

Stress (Physiology)
Electrodes, Carbon.


Includes bibliographical references (pages 63-67)



Number of Pages



South Dakota State University


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