Research Of Multi-physics Field Particle Sorting Based On Inertial Expansion And Contraction Channels

Microfluidics has received widespread attention in the fields of biological analysis,medical detection and environment monitoring due to its advantages of low sample throughput,short analysis period,high detection sensitivity and high integration,while cell sorting plays a crucial role in cell biology,cell based diagnosis and cure,therefore it is essential to study how to achieve high accuracy and high efficiency sorting of cells with high throughput.At present,the microfluidic chip for cell sorting mainly includes inertial sorting,dielectrophoretic sorting,microfiltration sorting,sound surface wave sorting,etc.Each sorting method has its own characteristics,among which inertial sorting is widely used due to the advantages of high sorting throughput and simple structure.In this paper,based on the group’s previous research,the inertial sorting technique was studied in depth and combined with deterministic lateral displacement and dielectrophoresis sorting techniques to form a multi-physical field sorting structure.The polystyrene spheres(PS)and silica microspheres were used to simulate real cells for particle sorting experiments,and some progress was achieved in achieving high particle sorting efficiency and high sorting accuracy with high throughput.The main results of the work were as follows:(1)A multi-physical field particle sorting chip based on an inertial scaling channel with deterministic lateral displacement cascade was proposed to combine the two passive sorting methods to achieve high accuracy and efficiency in sorting particles with large size differences at high throughput.This chip was easy to integrate and had the advantages of sheathless,simple structure,and without matching of the flow resistance which consisting of one one entrance,two exits and the main channel.The particle flow rate and trajectory were simulated and analysed using simulation software to optimise the structural parameters.Particle sorting experiments were performed using different sizes of polystyrene spheres(simulating biological cells)to demonstrate the focusing and sorting effects of 5 μm and 20 μm PS particles at different flow rates and to verify the sorting performance.Using 5 μm PS spheres as the target particles,the sorting efficiency was 99% and the sorting purity was 96.1% at a flow rate of 300 μL/min.The optimum flow rate for particle sorting was determined based on the sorting effect and applied to 5 μm and 10 μm polystyrene spheres,and the average sorting efficiency and sorting purity were 93.1% and 90.4% for the 5 μm and 10 μm PS particles respectively.The integrated chip showed excellent sorting results for particles with large size differences under high throughput conditions.(2)For the different electrical properties of particles,a multi-physical field particle sorting chip based on a combination of inertial scaling channels and planar electrode structures was proposed.By using planar electrodes to produce a dielectrophoretic force that was proportional to the size of the particles and the magnitude of the electric field intensity,positive or negative depending on the CM factor number characteristics,the structure was able to achieve the particle sorting based on both the difference of particle size and the different dielectric properties of the particles.Simulation software was used to optimise the chip structure parameters and fabricated the particle sorting microchip by analysing the effects of parameters such as the flow field distribution of the planar electrodes,the electric field distribution,the electrode width and distance,and the dielectrophoretic force on the particles.The particle sorting effect of 4 μm and 10 μm PS particles was investigated at a flow rate of 14 μL/min and a solution conductivity of 1 μS/cm.After several experimental tests,the particle sorting efficiency and sorting purity were 96.1% and 94.5% by using 4 μm PS as the target particles.The chip showed high sorting efficiency and purity for particles with different dielectric properties but similar sizes.(3)In order to meet the demand for high sorting efficiency and high sorting purity of multiple cells with high throughput in microfluidic chips,a particle sorting chip cascaded with an inertial CEA channel and a three-dimensional electrode structure was developed.The particle flow field distribution,electric field density and particle trajectory in the channel were analysed by simulation software,and the 3D electrode processing process was explored to design and prepare the microfluidic sorting chip.The optimum flow rate conditions were determined by performing sorting tests on 4 μm and 20 μm PS particles at different flow rates and different solution conductivities.Under these conditions,the sorting efficiencies of 4 μm and 20 μm PS spheres and 4 μm Silica microspheres exceeded 97% and the sorting accuracies exceeded 95% with stable results.