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    Microfluidic device with 3D electrode structure for high throughput dielectrophoretic applications
    (2014-10) Zeinali, Soheila
    Microfluidics is the combination of micro/nano fabrication techniques together with knowledge of fluid behavior at the microscopic level to pursue powerful techniques in controlling, manipulating and measuring chemical, physical and biological processes at micro/nano scale. Sorting and separation of bio-particles are highly considered in diagnostics and biological analyses. By implementing the characteristics of microscale flow phenomenon, dielectrophoresis (DEP) has offered unique advantages for microfluidic devices. In DEP devices asymmetric pair of planar or three dimensional (3D) electrodes could be employed to generate non-uniform electric field. In DEP applications, facing 3D sidewall electrodes is considered to be the key solution of increasing device throughput because of producing homogeneous electric fields along the height of microchannels. Despite all advantages, fabrication of 3D vertical electrodes requires considerable challenge. In this thesis, in order to highlight the advantage of 3D electrodes over planar electrodes, the simulations are performed. Based on the developed computational model, the design parameters are decided. For the fabrication of the device, two different fabrication techniques have been proposed. In the first method, both the mold and the electrodes are fabricated using high precision machining. In the second method, the mold is fabricated with tilted sidewalls using high precision machining and the electrodes are deposited on the sidewall using sputtering together with a shadow mask fabricated using wire electric discharge machining (WEDM). The both techniques are assessed as highly repeatable and robust methods. Only the manipulation of particles with negative-DEP has been demonstrated in the experiments, and the throughput values up to 105 particles/min have been reached in a continuous flow.