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

Inertial microfluidics have shown its particular capability to manipulate micro-scale particles in a simple, highthroughput, 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 mu m 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 mu m) 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.

Automated summary

A novel microchannel structure was developed for flow-rate and particle-size insensitive inertial focusing; efficient focusing of particles and tumor cells at different flow rates was achieved through enhanced secondary flow; providing important reference for the development of portable inertial microfluidic devices.