Flow-rate and particle-size insensitive inertial focusing in dimension-confined ultra-low aspect ratio spiral microchannel

Abstract

Inertial microfluidics have shown its particular capability to manipulate micro-scale particles in a simple, high-throughput, and passive manner. Up till now, inertial focusing approaches remain challenging in the quest to achieve both flow-rate and particle-size insensitive focusing with simple design and robust operation. In this research, we develop a dimension-confined ultra-low aspect ratio spiral microchannel to realize flow-rate and particle-size insensitive inertial focusing. Equally distributing microstructures in the spiral microchannel, the secondary flow enhancement is explored by the computational fluid dynamics simulation. Utilizing the accelerated secondary flow, 15.5 µm polystyrene fluorescent particles are efficiently focused (>99%) in the similar position of microchannel within a wide range of flow rates (0.5–3.5 mL/min) during a long operation duration (0–60 min). Further, different sized particles (7.3, 9.9 and 15.5 µm) are all well focused (>90%) near the inner wall when different flow rates (1–3 mL/min) are applied. Similarly, three types of tumor cells (K562, HeLa and MCF-7) are successfully focused in the same position of the microchannel under high flow rates (1.5–2.5 mL/min). The enhanced secondary flow in our channel enables the flow-rate and particle-size insensitive inertial focusing in a sheath-less, high-throughput, and easy-to-fabricate manner, which is promising for development of portable inertial microfluidic device for flow cytometry, online sample processing, and so on.