Ultra-low aspect ratio spiral microchannel with ordered micro-bars for flow-rate insensitive blood plasma extraction

The ability to regulate secondary flow is significant for efficient particle/cell focusing. Microfluidic technologies have accomplished impressive progress in particle/cell manipulation with the help of the Dean effect. Herein, we explored blood cell focusing with the ultra-low aspect ratio inertial microfluidic system which uses the geometric confinement to enhance the secondary flows to different degrees. Introducing a series of micro-bars in the spiral microchannels accelerates the secondary flow, which can greatly enhance highly-efficient particle/cell focusing under various flow rates. Further, plasma extraction can be successfully achieved from 15 x diluted whole blood in an easy-to-use (without the assistance of sheath fluid and complex manufacturing of multi-layer structure), high and wide flow rates (1-5 mL/min, exhibiting no parallel construction design), long-term (at least 60 min), stable (processing at least 300 mL blood samples with consistent efficiency), and highly-efficient (99.99% blood cell rejection ratio) manner. Compared with previously-reported technologies, the engineering strategy of secondary flow in our designed dimension-confined spiral channel provides a balanced overall performance for plasma separation pointing to ease-to-fabrication, insensitive to flow-rate, high throughput and operation efficiency.