Research On The Characteristic Of Particle Inertial Focusing Based On Microfluidic Technology

Microfluidics is a technology that manipulates fluids on a micro-scale to achieve functions such as detection and analysis.It is also called lab on a chip or microfluidic chip and is one hot topic of the cutting-edge multi-disciplines.Microfluidic chips have the advantages of high integration,saving reagents,high controllability,and low cost.They have shown great potential in in-vitro diagnostics,chemiluminescence,and clinical research.Inertial microfluidic particle focusing and sorting has many advantages,such as simple structure,easy operation,and good biological applicability.Therefore,it has enormous application potential in cell counting and screening.However,the current research on particle focusing in inertial microfluidic is still in the stage of the phenomenological study.Understanding the particle migration characteristic in the shrinkage-expansion array channel is not enough,and the channel structure needs to be further enriched to improve particle focusing and sorting performance.For this reason,the interaction model between particles and fluids was used to numerically study the focusing and sorting characteristics of particles in the microchannels with the shrinkage-expansion array.First,the model of fluid acting on particles is used to simulate the dynamic behavior of the particles in the shrinkage-expansion array microchannel;the influences of the shrinking-expanding angle,inlet flow rate,and particle size on the focusing behavior are studied.Secondly,a single-inlet multi-sheath fluid shrinkage-expansion array microchannel is proposed.The fluid-particle interaction model is used to simulate the dynamic behavior of particles in the microchannel.The effects of the sheath angle,sheath position,sheath number,and sheath fluid flow are studied on the focusing and sorting characteristics.Finally,to improve particle focusing and sorting performance,the array channel is spiraled to intensify Dean drag force.The influences of channel aspect ratio,spiral length-to-width ratio,and channel Reynolds number on particle focusing characteristics were studied.The main conclusions are as follows:1)When the asymmetric shrinkage-expansion microfluidic chip with no sheath fluid has a contraction-expansion angle α of 90°,the flow disturbance caused by the contraction-expansion structure is the strongest the particle focusing effect is the best.The particles of 7 μm and above can be entirely focused in this optimized design.The Reynolds number has a weak impact on the focusing effect of 15 μm particles.When the flow rate is increased,the processing capacity can be improved.It is found that the suffering force of particles changes periodically with the length of the channel.The structure adopted in this paper can realize the sorting of particles with a particle size of≥15 μm and 1～3 μm.2)A single-induction multi-sheath fluid asymmetric contraction-expansion array microchannel is proposed.Due to the difference in flow channel structure required for particle focusing and sorting,this paper has obtained the optimal flow channel structure corresponding to 15 μm particle focusing and particle sorting between 3 μm and 15 μm.Furthermore,analyzing the force in the focusing direction of 15 μm particles,the correlation equation of the minimum channel length required for complete focusing of different particle sizes was fitted.Finally,the accuracy of the correlation equation was verified.3)Study on the dynamic behavior of spirals asymmetric contraction-expansion microfluidic particles with a single introduction of multiple sheath fluid.When the spiral aspect ratio is 9:11 and the channel height is 40 μm,the particle focusing effect is the best;when the channel Reynolds number is greater than 57.3,the separation of 5 μm and10 μm particles can be achieved.When the Reynolds number is greater than 76.4,the separation of 5 μm and 15 μm particles can be achieved.