Date of Graduation

5-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Electrical Engineering

Advisor/Mentor

Omar Manasreh

Committee Member

Timothy Muldoon

Second Committee Member

Simon Ang

Third Committee Member

Jiali Li

Fourth Committee Member

Jingxian Wu

Keywords

Electrochemical Sensor, Glucose Sensor, Glycated Hemoglobin, Nanostructures, Optical Sensor, ZnO Nanorods

Abstract

The purpose of this research is to design and fabricate sensors for glucose detection using inexpensive approaches. My first research approach is the fabrication of an amperometric electrochemical glucose sensor, by exploiting the optical properties of semiconductors and structural properties of nanostructures, to enhance the sensor sensitivity and response time. Enzymatic electrochemical sensors are fabricated using two different mechanisms: (1) the low-temperature hydrothermal synthesis of zinc oxide nanorods, and (2) the rapid metal-assisted chemical etching of silicon (Si) to synthesize Si nanowires. The concept of gold nano-electrode ensembles is then employed to the sensors in order to boost the current sensitivities by enhancing the rate of electron transfer during the electrochemical reaction. High crystallinity and good alignment of the nanostructures lead to increase in the electrode surface area, thereby leading to higher current sensitivities compared to other published works.

My second research approach is to design an optical sensor for evaluating long-term glycemic state in diabetic patients. Glycated hemoglobin (HbA1c) is a minor component of blood hemoglobin to which glucose is bound. The HbA1c test is a common medical test used to indicate the average blood glucose level over the past 12-16 weeks. The National Institute of Diabetes and Digestive and Kidney Diseases has established a direct relationship between the percentage of HbA1c and the blood sugar level. Our sensor instrumentation design is based on the Beer’s law of optical absorption. Major device components include two commercial light emitting diodes, a cuvette holder, a Si photodiode, and an ATmega328P microcontroller. It is observed that the absorbance of diluted HbA1c samples and the corresponding photodiode output voltage are inversely related. The photodiode voltages as a function of HbA1c percentage concentrations show an exponentially decaying curve. An algorithm for multiple variable regression analysis is then used for sensor calibration. The percentage of HbA1c is then anticipated based on the obtained output voltage using the calibrated curve results. The proposed portable optical sensor proves to be a promising step towards the prediction of the long-term glycemic levels in diabetic and pre-diabetic patients non-invasively.

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