Hydrodynamic Focusing for a Micromachined Flow Cytometer

TLDR

Flow cytometry analyzes and sorts cells by exploiting hydrodynamic focusing and cellular characteristics. The study aims to describe hydrodynamic focusing within a micromachined flow cytometer. The authors model the focusing using potential flow theory, numerically simulate the flow field, systematically study geometry and flow‑rate effects, design and fabricate a plastic micromachined flow chamber, and verify focusing by microscopic visualization. Experiments show the focused sample stream can be narrowed to ~3 µm, enabling cell sorting and counting.

Abstract

This paper describes hydrodynamic focusing inside a micromachined flow cytometer. Flow cytometry is a process whereby cells are analyzed and sorted based on hydrodynamic focusing phenomenon and specific cellular characteristics. In this study, the hydrodynamic focusing phenomenon is first modeled by employing potential flow theory. Then the flow field inside the flow cytometer is numerically simulated. The effect of the device geometry and relative sheath and sample flow rate on the focusing of the center flow is explored systematically. At last, a micromachine-based flow chamber is designed and fabricated on plastic substrates as a micro flow cytometer. Hydrodynamic focusing is verified with the use of microscopic visualization of water sheath flows and dye-containing sample flow. Experimental data indicate that the size of focused sample stream can be reduced to about 3 μm, which is applicable to cell sorting and counting.