Red blood cell and white blood cell separation using a lateral-dimension scalable microchip based on hydraulic jump and sedimentation

In most microfluidic techniques, channel width must be in range of few tens of micrometers for the device to work properly. With these dimensions, low-cost mass-production of microfluidic devices for use in point-of-care test is an issue. Here we present a hydraulic jump-based technique for size-selective microparticle or cell sorting in which working mechanism is not affected by channel width. Similar to converting kinetic energy to potential energy in macro scale, high-speed flow in a microfluidic channel is intentionally transformed into a flow with high potential energy by adjusting the channel height, inducing hydraulic jump. Depending on the strength of this energy transformation, particles with appropriate sizes can be trapped in a designed location as a result of sedimentation. With properly designing lengths of multiple expanded-height chambers and controlling the flow rate, it is possible to trap and release particles or cells selectively based on their size. To demonstrate application of our technique, we enriched 9.77 and 4.95 μm microbeads as well as WBCs and RBCs in separate chambers. Experimental results showed >90 % selective enrichment of microbeads based on size. In addition, 69 % of WBCs and 80 % of RBCs were trapped in the first and second chamber, respectively.