Inertial Separation of Particles Assisted by Symmetrical Sheath Flows in a Straight Microchannel

Over the past two decades, inertial microfluidics, which works at an intermediate range of Reynolds number (∼1 < Re < ∼100), has been widely used for particle separation due to its high-throughput and label-free features. This work proposes a novel method for continuous separation of particles by size using inertial microfluidics, with the assistance of symmetrical sheath flows in a straight microchannel. Here, larger particles (>3 μm) are arranged close to the channel sidewalls, while smaller particles (<2 μm) remain flowing along the channel centerline. This conclusion is supported by experimental data with particles of different sizes ranging from 0.79 to 10.5 μm. Symmetrical Newtonian sheath flows are injected on both sides of particle mixtures into a straight rectangular microchannel with an aspect ratio (AR = height/width) of 2.5. Results show that the separation performance of the developed microfluidic device is affected by three main factors: channel length, total flow rate, and flow rate ratio of sheath to sample. Besides, separation of platelets from whole blood is demonstrated. The developed microfluidic platform owns the advantages of low fabrication cost, simple experiment setup, versatile selections of particle candidates, and stable operations. This systematic study provides a new perspective for particle separation, which is expected to find applications across various fields spanning physics, biology, biomedicine, and industry.