Microfluidic Chip For Dielectrophoretic Separation Of Particles Based On Novel3D Electrodes

Separations of micron-sized particles are of great importance in a large numberof applications in many fields, such as biomedical diagnosis, biochemical analysis,food safety, and environmental monitoring. Some of the conventional separationtechniques are centrifugation, flow cytometry, chromatography, andfluorescence-activated cell sorters. Dielectrophoretic separation, based onmicrofluidic chips, attracted wide research concerns dealing with its benefits interms of reduced sample volume, cost of reagent, analysis time, and feasibility inpackaging. However electrodes used in dielectrophoretic separation are usually hardto be integrated with other microfluidic components which hinder the popularity ofthis technique.Hence, this study focuses on developing a new type of dielectrophoreticseparation chip. These chips are based on3D electrodes that are easily assembled.The following thesis analyzed the principle of dielectrophoretic separation,simulated the particle-separating process, designed and fabricated a three-layeredseparation chip, built a particle separation system based on the fabricated chip, andperformed some particle-separating experiments.First we studied the principle of dielectrophoretic separation of particles inmicrofluidic chips. This includes flow property in microchannels, external forcesexerting on particles, dielectrophoretic force expression, dielectrophoreticproperties of polystyrene particles and yeast, and the movement of particles inmicrochannels.Then we designed a microfluidic chip for separation of particles with differentcharacteristics and carried out the finite element simulations. A three-layeredseparation chip was simplified to a2D model for the simulation. We then calculatedthe distribution of flow field, electric field, and dielectrophoretic force in the mainchannel. After that we predicted the trajectory of particles before optimizing thecrucial parameters for the chip.Afterwards, we fabricated a separation chip by using MEMS techniques. Atfirst we created the three layers of the chip, these are the substrate, the3Delectrodes, and the microchannels which were all developed using ITO, AgPDMS,and PDMS respectively. These three layers were integrated into a chip, after whichthe basic performance of the chip was tested. Finally, experiments of particle separation were performed using the fabricatedchip which includes the building of a separation platform, the preparation ofexperimental samples, and the separating experiments.Through the research provided by this thesis, we developed a microfluidic chipby integrating3D electrodes with PDMS channels that successfully separatedparticles of different size or different electric properties depending on the sampleused. The performance of the chip shows promising application potential for theseparation of human cells.