Microfluidic separation of the live and dead bacteria cells in the sensor of the bacteriological quality of water

• Main Author: Liew, Jun Bin.
• Other Authors: Volodymyr Ivanov
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Environmental engineering::Water supply
• Online Access: http://hdl.handle.net/10356/16908
• Institution: Nanyang Technological University

There is a interest in developing the low cost microfluidic device for separation of live and dead bacterial cells which can be applied in sensor for bacteriology of water and wastewater quality. There are several researches have been done in this area and this report is mainly focus on two technologies, hydrophobic interaction chromatography and dielectrophoresis. The objective of this project is to investigate separation efficiency of hydrophobic chromatography separation and preparation of experiment set up for dielectrophoresis. Hydrophobic interaction chromatography mainly applied in petroleum and food science area to extract the pure particles and protein. However, this technology still have not applied and experimented in live and dead bacterial cells separation. Dielectrophoresis is defined as the motion of neutral or charged particles that have undergone polarization as a result of being placed in a non uniform electrical field. For past few years, several researches had been done in this area in order to find out the efficiency of this technology applied in live and dead bacterial cells separation. Escherichia coli were used as tested bacterial cells since it is an ideal indicator organism to test environmental samples for fecal contamination. Total four experiments have been done for hydrophobic chromatography separation. There were pure PBS chromatography, pure live cells (100% live cells) separation, pure dead cells (100% dead cells) separation and live and dead cells (50% live cells and 50% dead cells) separation. A simplified hydrophobic chromatography system had been set up and results would be measured by optical density spectrophotometer, luminescence spectrometer and imaged by fluorescence microscope. As for dielectrophoresis, procedure about fabrication of PDMS based microchannel and preparation of experiment was discussed. Set up of experiments also be discussed. As results obtained from the pure live cells and pure dead cells hydrophobic chromatography separation, it showed that live cells would trap in the chromatography system due to hydrophobic interaction between live cells and hydrophobic materials and dead cells will elute out from chromatography system. As for mixture of live and dead bacterial cells separation, the separation was observed from the results by luminescence spectrometer. As for dielectrophoresis, this report discussed about theoretical relationship between Clausius-Mossotti function and frequency applied by external electric. This relationship is main component that affect the signal of dielectrophoretic force and affecting separation of cells. The theoretically discussion shown that at frequency of 107 Hz, the dead bacterial cells will encounter negative dielectrophoretic force which moving them toward lower electric field intensity.