| 总结: | <p>Magnetic particle separation in microfluidic systems is a method for enriching or isolating biological entities such as cells or biomarkers of diseases using magnetic beads that covalently bind to a target; it is compatible with lab-on-a-chip technology and has potential to be integrated with other functional blocks. This thesis describes the operation of a magnetic particle separator using a novel configuration of permanent magnets to provide higher separation efficiency with minimum trapping of particles. The novel magnet configurations consisted of two (Double Magnet) or four (Quadrupole) rectangular permanent magnets arranged around a microfluidic channel. The magnet configurations guide magnetic particles along adjustable trajectories by simply varying the separation distance between the magnets or their aspect ratio. Influence of the salient geometrical parameters on the behaviour of the trajectory was studied and experimental verifications are presented using particle suspensions of 1 μm and 2.8 μm sized magnetic beads. In addition, it was discovered that the magnetic beads gather along a line that can be uniquely positioned within the fluidic cell leading to improved performance. </p> <p>The performance of the magnetic separator was studied for five magnetic particle types by simulating 400 individual particle trajectories following an Eulerian-Lagrangian model. The model incorporated experimentally found particle properties such as size and susceptibility. Magnetic separation was performed in continuous flow and pulse mode operation. In continuous separation a maximum separation efficiency of 35% and 55% was found experimentally for the Double Magnet and Quadrupole configuration, respectively, and in pulse mode operation a separation efficiency of more than 80% could be achieved in experiments and simulations.</p> <p>Further, in order to improve the accuracy of the magnetophoretic force calculations, the magnetic responsiveness of the particle types across a magnetic field range of 38-70 mT was studied using a particle tracking system and SQUID relaxometry. The susceptibility of all particle types showed a magnetic field dependence and a promising correlation between the two measurement techniques could be found.</p>
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