Numerical and Experimental Investigation of Microfluidic Devices for Manipulation of Microentities

Abstract

The thesis work aims to introduce low-cost microfluidic Lab-on-a-Chip microdevices for controlled manipulation of a variety of biological micro-objects, such a blood cells and circulating tumor cells. A particle-based simulation technique called Dissipative Particle Dynamics (DPD) technique was first employed to design multiple microfluidic devices for investigating the motion of biological micro-objects at low Reynolds numbers. A DPD inhouse FORTRAN code was developed to simulate the trajectories of single and multiple microparticles in the presence of the hydrodynamic forces, a transverse deflecting force, and inter-particle interaction forces. The Dielectrophoresis (DEP) force was investigated as a case study for the transverse deflecting force and the particle-particle interactions between biological micro-object were described using a simplified version of the Morse potential. Multiple microfluidic devices with different configuration of microelectrodes were numerically designed to investigate the dielectrophoretic behavior of biological micro-objects in four basic operations: (i) focusing of bioparticles into a single stream in the middle of the microchannel, (ii) switching of the target micro-objects to any desired outlet, (iii) medium exchange and dipping of the target micro-objects, and (iv) separation of target objects from a sample of heterogeneous micro-objects. The DPD simulation results were verified and validated against previously reported numerical and experimental works in literature. The computationally designed microdevices were fabricated by employing standard lithographic techniques, and experiments were conducted using red blood cells and MDA-MB-231 cancer cells as the representative biological micro-objects. Red blood cells suspended in an isotonic sucrose/dextrose medium were used to perform the operations of focusing, switching, medium exchange, and dipping operations. The intercellular interaction force was to found to have a negligible effect in continuous-flow based motion of RBCs under the DEP force. Finally, the separation of MDA-MB-231 cancer cells from healthy blood cells was also demonstrated in the experiments. The experimental results in all the targeted operations showed good agreement with the numerical results.

Date of Award	Dec 2019
Original language	American English