A passive microfluidic device for continuous microparticle enrichment

: A passive microfluidic device is reported for continuous microparticle enrichment. The microparticle is enriched based on the inertial effect in a microchannel with contracting-expanding structures on one side where microparticles/cells are subjected to the inertial lift force and the momentum-change-induced inertial force induced by highly curved streamlines. Under the combined effect of the two forces, yeast cells and microparticles of different sizes were continuously focused in the present device over a range of Reynolds numbers from 16.7 to 125. ∼68% of the particle-free liquid was separated from the sample at Re = 66.7, and ∼18 μL particle-free liquid was fast obtained within 10 s. Results also showed that the geometry of the contracting-expanding structure significantly influenced the lateral migration of the particle. Structures with a large angle induced strong inertial effect and weak disturbance effect of vortex on the particle, both of which enhanced the microparticle enrichment in microchannel. With simple structure, small footprint (18 × 0.35 mm), easy operation and cell-friendly property, the present device has great potential in biomedical applications, such as the enrichment of cells and the fast extraction of plasma from blood for disease diagnose and therapy.