Sample Preparation of Biofluids Using Microscale Vortices

Analysis of cellular samples is widely used for medical diagnostics. While there has been significant progress made in developing cell detection and analysis technologies, the development of miniaturized and automated tools to prepare cellular specimens for sample analysis quietly lags behind. Sample preparation continues to be performed off-chip with macroscale instruments, like the bench top centrifuge, which limits the use of cell-based diagnostics in point-of-care settings, and increases the cost of tests through manually-performed steps. This dissertation reports the development of a miniaturized microfluidic device that recapitulates the high-throughput operations of enrichment and concentration of a standard laboratory centrifuge. The "Centrifuge Chip" employs unique inertial fluid physics to selectively isolate larger cancer cells from bloody samples using laminar fluid microvortices. Specifically, cancer cells are captured in vortices while smaller leukocytes and erythrocytes are not stably trapped in vortices and are significantly reduced in the collected concentrated sample. This unique cell trapping mechanism was explored to systematically understand particle and cell behavior in microvortices and to design deterministic and predictable vortex trapping systems for biological and clinical applications. The design rules were employed to develop a tool for 1) isolating rare circulating tumor cells from blood of cancer patients and 2) harvesting large quantities of cancer and mesothelial cells from pleural and peritoneal effusions. By selectively enriching larger cells over a background of red and white blood cells, the miniaturized centrifuge replaces the traditional centrifugation step in the clinical lab while also potentially enabling more sensitive analysis of pure preparations originating from a larger volume. Ultimately, the Centrifuge Chip is an instrument that increases reproducibility of cell-based protocols, minimizes manual handling steps, reduces reagent costs via label free biomarker, and potentially revolutionizes traditional sample preparation procedures