CFD schematic of "microfluidic drifting"
The planar nature of standard microfluidic manufacturing processes only facilitates 2D focusing. Current 3D hydrodynamic focusing devices require tedious assembly of individual components and multiple alignments and exposures during mold fabrication. These limitations increase cost and complexity. The disclosed invention introduces a novel fluid manipulation technique “microfluidic drifting” to allow 3D hydrodynamic focusing with a simple single layer planar microfluidic device. The method is effective, robust, and requires only standard soft lithography fabrication methods. 3D hydrodynamic focusing is accomplished in a 2-step sequence: (1) focus sample flow in the vertical direction using “microfluidic drifting” and (2) focus in the horizontal direction using two horizontal focusing sheath flows. Switching between static flow and 3D focusing takes <3s and is highly repeatable.
Application & Market Utility
This invention permits many applications otherwise impossible due to the current limitations of impractical and specialized 3D microfabrication techniques required for 3D hydrodynamic focusing. The mechanism of 3D focusing is illustrated in the figure above using a computational fluid dynamics simulation. This invention allows 3D focusing with a single-layer planar device fabricated using soft lithography. Vertical and horizontal compression ratios can be easily altered by changing flow rates.
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