| Microfluidics processes or manipulates small (nanoliter to picoliter) amounts of fluids using channels with dimensions of tens to hundreds of micrometers. Pinched Flow Fractionation (PFF), as a continuous separation method without outer field, shows great potential on particle separation based on particle size. PFF device can be manufactured quickly and cheaply, and can continuously separate blood cells, micro bubbles, and genotype single nucleotide polymorphisms (SNPs) without destroying their integrality.Three velocity theoretical models for the PFF devices were compared to calculate the critical diameters of each outlet. The numerical simulation was done by the solver FLUENT. The effects of flow rate ratio of inlet2to inlet1was calculated. By adjusting the pressure upon outlet I, particles could be successfully separated. Two kinds of PFF devices were designed to divide polystyrene particles of2.0μm and14.6μm. The effects of flow rate ratio and total flow rate on the separation efficiency were examined. The conclusions are obtained as follows:1. A semi-circle velocity model was proposed based on the FLUENT simulation result and velocity profile in the cross-section. The3D-velocity profile achieved by Mathematica showed great similarity to semi-circle flow profile instead of parabolic flow profile.2. The simulation result of FLUENT showed that a PFF device with30μm and40μm in the pinched part can separated14.6pm and2μm particles when the flow rate ratio is15and20, respectively; a PFF device with50μm in the pinched part can separate particles of10um and2μm in diameter, byu applying a1300Pa pressure upon outlet I with the flow rate ratio higher than30.3. Polystyrene particles with diameter of2.0μm and14.6n can be separated based on2outlets PFF devices with pinched segment width of30μm,40μm and45μm and13outlets devices with width of20μm. The influence of the total flow rate on separation efficiency was minor, therefore a fast particle separation could be achieved by improving the flow rate. |
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