Abstract
Microfluidics-based cell sorting to isolate target cells is frequently used in clinical diagnostic and therapeutic applications due to its precise and fast processing profile. Although active microfluidic cell sorting possesses the advantages of more precise manipulation on target cells, passive microfluidic enables label-free cell sorting without requirement of cell surface targeting sites in addition to low-cost of functional parts. Inertial microfluidics as one passive method for high throughput of cell sorting relies on differentiable cell size among the target cells and remaining populations. However, for cell sorting via inertial microfluidics, there are still obstacles to overcome, such as limited sorting resolution, conflicting between throughput and focusing of small-sized cells, versatility and simplicity of cell sorter, and the challenge of manipulation submicron vesicles. In this thesis, we have achieved the enhancement on sorting resolution of inertial microfluidics to submicron (0.5 µm) by presenting a novel channel design of periodic contractions on repeating curve in a Newtonian fluid without sheath flow. The presented design was utilized for purifying the Candida pathogens for molecular detection of bloodstream infection. We also found that the presented method of periodic contractions on repeating curve has a significant effect on enhancing the focusing of the small particles like 1 µm in a good-diluted non-Newtonian fluid (0.02% PEO solution) without sheath flow. Such method deserved high throughput of above 100 µL/minute and was applied to the purification of bacterial pathogens from the blood. The inertial microfluidic method has advantages in recovering 2 to 3 folds higher of the pathogen than the existing lysis centrifugation method. 3 Furthermore, a pressure-driven cell sorter was developed to integrate a series of inertial microfluidic chips for the different cut-off sizes of cell sorting. The presented cell sorter was then applied to white blood cells' isolation with 92% of recovery ratio and complete composition as the original sample and isolation of specific subpopulation (i.e., lymphocytes). This provides a low-cost and universal platform for size-based cell sorting with simple operations. Lastly, we successfully allowed the submicron vesicles and particles focused based on the size in the relatively large dimension of the channel (120 x 30 µm) to ensure the high throughput (200 µL/minute). 82% of the exosomes have been isolated from extracellular vesicles by the presented method, which used both sheath flow and non-Newtonian fluid.