published_or_final_version / abstract / Chemistry / Master / Master of Philosophy

This thesis research focuses on the characterization of thinfilms made of poly(vinylidene fluoride) (PVDF) using an atomic force microscope. Thinfilms of PVDF were fabricated by a spin coating method with different conditions and characterized using the Atomic Force Microscopy (AFM) for morphological changes. Phase and conformational changes of PVDF were investigated using both wide angle X-ray diffraction (WAXD) and Fourier Transform Infrared Spectroscopy (FTIR). From this analysis, in-situ corona poling with annealing of spin-cast PVDF enabled a phase change from α to the mixture of β and γ phases. This process can decrease the complexity of the conventional method which requires mechanical stretching before poling PVDF in addition to thermal annealing for β phase transformation. This thesis describes some materials and surface properties of solution-cast PVDF thinfilms with various conditions such as topography and phase image, adhesion force, friction force, and roughness. Through the AFM topography and phase images, polymeric behavior and spherulites are discussed in the later part of the thesis.

This thesis research focuses on the characterization of thinfilms made of poly(vinylidene fluoride) (PVDF) using an atomic force microscope. Thinfilms of PVDF were fabricated by a spin coating method with different conditions and characterized using the Atomic Force Microscopy (AFM) for morphological changes. Phase and conformational changes of PVDF were investigated using both wide angle X-ray diffraction (WAXD) and Fourier Transform Infrared Spectroscopy (FTIR). From this analysis, in-situ corona poling with annealing of spin-cast PVDF enabled a phase change from α to the mixture of β and γ phases. This process can decrease the complexity of the conventional method which requires mechanical stretching before poling PVDF in addition to thermal annealing for β phase transformation. This thesis describes some materials and surface properties of solution-cast PVDF thinfilms with various conditions such as topography and phase image, adhesion force, friction force, and roughness. Through the AFM topography and phase images, polymeric behavior and spherulites are discussed in the later part of the thesis.

Due to the high affinity and selectivity of aptamer selected from DNA library towards target proteins, the use of specific protein biomarkers to assist early diagnosis, and the recent rapid development of piezoelectric quartz crystal (PQC) biosensor technology, the research reported is focused on developing PQC biosensor using aptamers selected from a DNA library as selective coating for the detection of albumin in urine, two protein biomarkers for malaria in sera, and the determination of trace amount of SCV helicase protein from SAR in sera. Three new aptamer-PQC biosensors are developed with research conducted on aptamer selection, optimization of coating methods for aptamers on PQC, and coupling paramagnetic nanoparticle technology with PQC biosensor in flow injection analysis (FIA) to enrich analyte and eliminate sample matrix interference. A new approach for aptamer selection is successfully attempted in the development of the first aptamer-PQC biosensor with an aim to offer an early detection of microalbuminuria enabled by an increase in detection sensitivity with aptamer selected by its actual binding with albumin-PQC biosensor. The aptamer-PQC sensor developed has shown to give a working range between 0.1 to 10 ug/mL, a detection limit (S/N = 3, n=3) of 0.048 μg/ml, repeatability of RSD = 6.8% (n=3), a response time of 1 minute and a throughput of 60 samples/hour. The developed piezoelectric aptamer sensor is shown to have sufficient sensitivity to detect microgram quantities of albumin in urine. Aptamer-PQC biosensors are developed for the detection of two protein biomarkers, PfLDH for general diagnosis and PfHRP-2 for a specific diagnosis of Plasmodium falciparum malaria parasitemia, in sera. The results show satisfactory working range from 10-100 ng/mL for both PfLDH and PfHRP-2 protein biomarker, low detection limit of 1.8 and 4.7 ng/mL and satisfactory repeatability (%RSD, n = 3) of 7.4% and 9.2% for PfHRP-2 and PfLDH respectively. It is first report for aptamer based PQC biosensor to detect malarial PfHRP-2 and PfLDH at ppb range to meet the requirement for their diagnosis. To meet the highly demanding challenge for detecting protein biomarkers at pg/mL level in high-protein sera sample, the coupling of paramagnetic nanoparticle technology with aptamer-PQC biosensor was attempted for developing aptamer-PQC biosensor for selective detection of SCV helicase protein produced from SARS CoV replication. The coupling of aptamer coated paramagnetic nanoparticles for sample pretreatment to aptamer-PQC biosensor has shown to detect helicase protein in one-minute assay with a detection limit of 350 pg/mL. The aptamer-coated crystal exhibits a frequency shift linearly proportional to the concentration of SARS helicase from 1 to 1000 ng/mL with a correlation coefficient of 0.9975 and a repeatability of 6.8% (%RSD, n=3). After the enrichment procedure, recoveries of 102% and 119% were achieved using samples spiked with SARS helicase at concentrations of 10 ng/mL and 1.0 ng/mL respectively. It is the first report to detect for SCV helicase protein using PQC biosensor at pg/mL level after magnetic bead enrichment. / published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Thesis (M. Phil.)--University of Hong Kong, 2008. / Also available in print.

Dissertation (Ph.D.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references.

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

Fung, Kar Man. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 110-114). / Abstracts in English and Chinese. / 摘要 --- p.i / ABSTRACT --- p.ii / ACKNOWLEDGMENTS --- p.iii / TABLE OF CONTENTS --- p.iv / LIST OF FIGURES --- p.vi / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Background and Motivation --- p.1 / Chapter 1.2 --- Objective of the project --- p.4 / Chapter 1.3 --- Organization of the thesis --- p.5 / Chapter 2. --- Literature Review --- p.7 / Chapter 2.1 --- Control on Micro-Manipulation --- p.7 / Chapter 2.1.1 --- Visual Feedback Control --- p.8 / Chapter 2.1.2 --- Sensor-Based Feedback Control --- p.9 / Chapter 2.1.3 --- Bilateral Control --- p.9 / Chapter 2.2 --- Force Sensing System on Micro-Manipulation --- p.10 / Chapter 2.3 --- PVDF Sensor --- p.11 / Chapter 2.4 --- Summary of the Literature Review --- p.12 / Chapter 3. --- Micro-Manipulation --- p.14 / Chapter 3.1 --- Introduction of Micro-Manipulation --- p.14 / Chapter 3.2 --- Probe Station --- p.14 / Chapter 3.2.1 --- Micromanipulators --- p.15 / Chapter 3.2.2 --- Microscopes --- p.15 / Chapter 4. --- Piezoelectric Polyvinylidence Fluoride (PVDF) Sensor --- p.16 / Chapter 4.1 --- Charteristic of PVDF Sensor --- p.16 / Chapter 4.1.1 --- Piezoelectric Properties --- p.16 / Chapter 4.1.2 --- Dimensions of the PVDF Sensor --- p.18 / Chapter 4.2 --- Comparison of Piezoelectric Materials --- p.19 / Chapter 5. --- Theoretical Analysis of PVDF Sensor --- p.21 / Chapter 5.1 --- Sensitivity of PVDF Sensor --- p.21 / Chapter 5.2 --- Relationship between the Deflection and the Force of the PVDF --- p.22 / Chapter 5.3 --- Calculation of the Spring Constant K of the PVDF --- p.23 / Chapter 5.4 --- Simulation on the output from the PVDF Sensor --- p.23 / Chapter 6. --- Experimental Analysis of PVDF Sensor --- p.26 / Chapter 6.1 --- Force-Deflection Diagram --- p.26 / Chapter 6.2 --- Frequency Response of the PVDF Sensor --- p.27 / Chapter 7. --- 1-D PVDF-Based Sensing System --- p.30 / Chapter 7.1 --- Original Design of the Sensing System --- p.30 / Chapter 7.1.1 --- Plastic pipe and adapter --- p.31 / Chapter 7.1.2 --- PVDF Sensor --- p.32 / Chapter 7.1.3 --- Probe-tip holder --- p.32 / Chapter 7.2 --- Current Design of the Sensing System --- p.32 / Chapter 7.3 --- Analysis of the Sensing System --- p.34 / Chapter 7.3.1 --- Frequency Response of the Sensing System --- p.34 / Chapter 7.3.2 --- Sensitivity of the Sensing System --- p.41 / Chapter 8. --- Experiments on 1-D PVDF Sensing System --- p.49 / Chapter 8.1 --- Experimental Setup of the 1-D Sensing System --- p.49 / Chapter 8.1.1 --- Programmable Micromanipulator --- p.50 / Chapter 8.1.2 --- Charge Amplifier --- p.51 / Chapter 8.2 --- Calibration of the 1-D Sensing System --- p.53 / Chapter 8.2.1 --- Noise Signal from the system --- p.53 / Chapter 8.2.2 --- Signal from vibration --- p.55 / Chapter 8.3 --- Experimental Results on touching a substrate --- p.60 / Chapter 8.3.1 --- Description --- p.60 / Chapter 8.3.2 --- Results from touching a substrate --- p.62 / Chapter 8.3.3 --- Analysis of the deflection after touched a substrate --- p.67 / Chapter 8.4 --- Experimental Results on touching a micro mirror --- p.68 / Chapter 8.4.1 --- Description --- p.68 / Chapter 8.4.2 --- Results --- p.70 / Chapter 8.5 --- Experimental Results on lifting a mass platform --- p.74 / Chapter 8.5.1 --- Description --- p.74 / Chapter 8.5.2 --- Results --- p.76 / Chapter 9. --- Modification of 1-D Sensing System --- p.79 / Chapter 9.1 --- Design of the system --- p.79 / Chapter 9.2 --- Experimental Setup of the system --- p.80 / Chapter 9.3 --- Experimental Results on lifting a mass platform --- p.81 / Chapter 10. --- 2-D PVDF-Based Sensing System --- p.90 / Chapter 10.1 --- Design of the Sensing System --- p.90 / Chapter 10.2 --- Experimental Setup --- p.91 / Chapter 10.3 --- Calibration of the 2-D Sensing System --- p.92 / Chapter 10.3.1 --- Noise Signal from the system --- p.92 / Chapter 10.4 --- Experiments Results on touching a substrate --- p.94 / Chapter 11. --- Experimental Analysis --- p.97 / Chapter 11.1 --- Data Acquisition --- p.97 / Chapter 11.2 --- Spectrum Analysis of the Experimental Data --- p.101 / Chapter 12. --- Conclusion --- p.103 / Chapter 13. --- Future Work --- p.105 / Chapter 13.1 --- Control of the Sensing System --- p.105 / Chapter 13.2 --- Tele-operation System on force feedback sensing system --- p.107 / Chapter A. --- Appendix --- p.109 / Chapter A. 1 --- Procedures in using probe station --- p.109 / Bibliography --- p.110

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--Auburn University. / Abstract. Vita. Includes bibliographical references (p. 190-202).