| Summary: | 博士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 101 === Nowadays, emerging infectious diseases seem to appear in an endless stream all over the world, and the mutation of microbes makes problems in the use of antibiotics. How to improve the diagnostic efficiency and reduce the antibiotic misuse were important issues that researchers are studying. Dielectrophoresis (DEP) for the manipulation of cells, microbes, viruses and DNA, has been widely integrated into microfluidic chips or min devices for manipulating specific targets accurately. In this thesis, three subjects will be introduced, I. Microbial quantification based on grayscale image processing in a DEP chip The first part is the quantification of bioparticles based on the grayscale image processing (GIP) in the DEP-based microfluidic chip. The polystyrene beads were used as the sample particles to test for the feasibility of this approach; and then, the Candida cells were tested by GIP method to compare the standard counting of hemocytometer. The detection range of sample concentration is around 105-107 cells/ml, and the experimental time does not exceed 30 min. Ⅱ. Dielectrophoresis-based antibiotic susceptibility test The second part is the screening of the antibiotic susceptibility of Gram-negative bacteria (GNB) based the changes in their DEP behaviors. The -lactam antibiotics, whose function is to inhibit the cell wall synthesis, were used as the sample drugs to treat GNB. The -lactam-induced cell elongation happens in drug susceptible bacteria, and the significant change in DEP behavior can be observed at the inhibitory concentration within two hours. The antibiotic susceptibilities of important clinical pathogens (Escherichia coli and Klebsella pneumoniae) to -lactam antibiotics were tested by dielectrophoresis-based antibiotic susceptibility test (d-AST), and compared with the results of the standard culture method. In summary, the techniques of electrokinetics and microfluidics were integrated into one device for rapidly detecting bacteria and their drug sensitivity. Most importantly, the time needed of bacteria growth can be reduced from days to hours, and the occurrence of multidrug resistant bacteria also can be avoided. Ⅲ. AC electrokinetic motions of colloidal particles on the electrically-induced wave structure In the last subject, we demonstrated the electrically-assisted lithography that the wave structures induced by non-uniform electric fields were fabricated on the interdigitated electrode (IDE) arrays, and then colloidal particles were manipulated on the wave structure. In low frequency (~30 kHz), AC electroosmosis (ACEO) is predominant that particles were transported along valleys of the wave structure. The DEP force became stronger as the frequency raised to hundreds of kHz (~200 kHz), and then particles were collected at peaks of wave structures. Particles also can be concentrated at specific positions via changing the AC waveform. In addition, the size-dependant particle separation on the wave structure was also performed. Different size particles (0.5 and 2 m) can be separated into two populations due to the joint effect of drag force and DEP force, as they were transported by ACEO along the valley of the wave structure. The wave structures were fabricated rapidly and simply through the DEP-assisted lithography; and further, the joint AC electrokinetic phenomena of particles under the non-uniform electric fields were observed. The cell assembly, pattern, transportation and separation are potential applications to be going to achieve.
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