Dielectrophoretic trapping and separation of waterborne pathogen

• Main Author: Guo, Shan Shan.
• Other Authors: Du Hejun
• Format: Final Year Project
• Language: English
• Published: 2011
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/44534
• Institution: Nanyang Technological University

This report illustrates the learning and researching experiments of that the author has undertaken throughout the final year project on dielectrophoretic trapping and separation of waterborne pathogen. The non-uniform AC electric field can interact with polarized particles in order to create an imbalance of forces on the induced dipole. This effect, causes the particles moving, is called dielectrophoresis or DEP for short. The report presents the effects of particles’ behaviour caused by the DEP force, by adjusting 3 different parameters, which are voltage, frequency and flow-rate. It includes the detail preparation procedure of each particles and fabrication processes of DEP chips. Live/dead E.Coli and E.Faecalis, yeast cell and polystyrene microbeads are tested with the DEP chips. The DEP chip uses 60 parallel electrode arrays inside the microchannel, where the particles are trapped at the edge of the electrode during the positive DEP force. The edge of the electrode is the highest electric field region. The positive DEP force makes the polarized particles move towards the strong field region. The opposite situation gives rise to negative DEP force, which causes the particles to move away from strong field region. The direction for particles to move is a function of frequency. The trapped particles can be flushed away by flow of the medium when the frequency reaches their corresponding cross over frequency. This phenomenon causes the separation of different waterborne pathogen occurring. The experimental observation shows the polystyrene microbeads are not affected by the DEP force. The trapping efficiency of live/dead E.Coli and E.Faecalis and yeast cell are increased by increasing the voltage and frequency. However, when the frequency reaches to the cross over frequency, it influences the particles’ behaviours switches from positive DEP to negative DEP. The cross over frequency can be changed by adjusting the voltage. Nevertheless, the flow-rate of the medium causes minor effect on the trapping and separation of waterborne pathogen.