Walter Scott, Jr. College of Engineering

Graduate Exam Abstract

Zhangjing Yi
M.S. Final
Sep 01, 2011, 2:00 pm
Engr C103B
Characterization of a Multi-Channel Photoluminescence-Based Fiber Optic Sensor System
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<p style="text-indent: 30px;">Measuring multiple analyte concentrations is essential for a wide range of environmental applications, which are important for the pursuit of public safety and health. Target analytes are often toxic chemical compounds found in groundwater or soil. However, <i>in-situ </i>measurement of such analytes still faces various challenges. Some of these challenges are rapid response for near-real time monitoring, simultaneous measurements of multiple analytes in a complex target environment, and high sensitivity for low analyte concentration without sample pretreatment. This thesis presents a low-cost, robust, multichannel fiber optic photoluminescence (PL)-based sensor system using a time-division multiplexing architecture for multiplex biosensor arrays for <i>in-situ </i>measurements in environmental applications. The system was designed based upon an indirect sensing scheme with pH or oxygen sensitive dye molecules working as the transducer that is easily adaptable with various enzymes for detecting different analytes. </p>

<p style="text-indent: 30px;">Characterization of the multi-channel fiber optic PL-based sensor system was carried out in this thesis. Experiments were designed with interests in investigating this system’s performance using the transducer without the biorecognition component thus providing reference figures of merit, such as sensitivity and limit of detection, for further experiments or applications with the addition of various biosensors. A pH sensitive dye, fluoresceinamine (FLA), used as the transducer is immobilized in a poly vinyl alcohol (PVA) matrix for the characterization. The system exhibits a sensitivity of 8.66×10<sup>5</sup> M<sup>-1</sup> as the Stern-Volmer constant, K<sub>SV</sub>, in H<sup>+</sup> concentration measurement range of 0.002 – 891 µM (pH of 3.05 – 8.69). A mathematical model is introduced to describe the Stern-Volmer equation's non-idealities, which are fluorophore fractional accessibility and back reflection. Channel-to-channel uniformity is characterized with the modified Stern-Volmer model. Combining the FLA with appropriate enzymatic biosensors, the system is capable of 1,2-dichloroethane (DCA) and ethylene dibromide (EDB) detection. The calculated limit of detection (LOD) of the system can be as low as 0.08 ?g/L for DCA and 0.14 ?g/L for EDB. </p>

<p style="text-indent: 30px;">The performances of fused fiber coupler and bifurcated fiber assembly were investigated for the application in the fiber optic PL-based sensor systems in this thesis. Complex tradeoffs among back reflection noise, coupling efficiency and split ratio were analyzed with theoretical and experimental data. A series of experiments and simulations were carried out to compare the two types of fiber assemblies in the PL-based sensor systems in terms of excess loss, split ratio, back reflection, and coupling efficiency. </p>

<p style="text-indent: 30px;">A noise source analysis of three existing PL-intensity-based fiber optic enzymatic biosensor systems is provided to reveal the power distribution of different interference components. The three systems are a single channel system with a spectrometer as the detection device, a lab-developed multi-channel system, and a commercial prototype multi-channel system both using a photomultiplier tube (PMT) as the detection device. The thesis discusses the design differences of all three systems and some of the circuit design alteration attempts for performance improvements. </p>


Adviser: Kevin L. Lear
Co-Adviser: N/A
Non-ECE Member: Jennifer L. Mueller, Mathematics
Member 3: Ali Pezeshki, Electrical and Computer Engineering
Addional Members: N/A,N/A

[1] Z. J. Yi, Z. Zhong, K. F. Reardon, W. N. Wang, M. Katragadda, and K. L. Lear, "A Multi-Channel Fiber Optic Photoluminescence System for Multiplex Biosensor Arrays," Optical Fibers and Sensors for Medical Diagnostics and Treatment Applications X in series Proceedings of SPIE, San Francisco, CA, vol. 7559, 2010

[2] Z. Yi, R. Yan, R. Safaisini, K. Lear, “Optimization of waveguide thickness for local evanescent field shift detection,” Integrated Optics: Devices, Materials, and Technologies XV in series Proceedings of SPIE, San Francisco, CA, vol. 7941, 2011

[3] R. J. Yan, N. S. Lynn, L. C. Kingry, Z. J. Yi, R. A. Slayden, D. S. Dandy, and K. L. Lear, "Waveguide biosensor with integrated detector array for tuberculosis testing," Applied Physics Letters, vol. 98, pp. 013702, Jan. 2011

Program of Study:
ECE 441
ECE 504
ECE 514
MATH 531
ECE 457
ECE 580
PH 521
ECE 699