Multiphysics Simulations Of Microfluidic Particle Separation Chips

Microfluidic particle separation technology is a key part of microfluidic chip technology,which is often used in biological detection,medical reagent preparation and other fields.The accuracy and safety of biological particles in the process of sorting are important factors to be considered in chip design.Traditional particle separation techniques(such as centrifugation and dissolution)require large sample size and low separation accuracy,and often cause irreversible damage to particles.With the development of science and technology,such traditional sorting technology cannot meet the requirements of modern medical field for low cost,high efficiency and high safety.Based on the flow effect of microscale and the external physical field,microfluidic sorting technology can complete the particle sorting process on a centimeter-level chip,also known as Lab on a chip.This kind of sorting chip has the advantages of miniaturization,high efficiency and integration,and has developed rapidly in recent decades.Microfluidic active sorting chip achieves the purpose of sorting by externally applied physical fields such as acoustic,optics,electricity and magnetism,combined with the flow in the chip.Compared with the passive sorting chip,the microfluidic active sorting chip has higher particle separation efficiency.However,active sorting chips often involve multi-phase flow,micro-scale flow,complex boundary flow,multi-physics field and other factors,and the separation mechanism is very complex.In order to understand the effects of multiple physical fields on particle separation in active sorting chips,numerical simulation is very important.The acoustic particle sorting chip,particle inertial focusing chip and dielectrophoresis sorting chip involve the coupling of multiple physical fields and complex flows.Based on the finite element method and the lattice boltzmann method,a set of numerical simulation models for multi-physics field sorting chip was established in this thesis,which made a contribution to the simulation field of microfluidic technology.Based on the above methods,this thesis analyzed the motion characteristics and deformation characteristics of particles of the three chips under the action of multiple physical fields and complex flow fields.The main research contents and achievements include:(1)The motion characteristics of particles in an acoustic sorting chip were studied:The finite element model of the acoustic sorting chip was established,the distribution of acoustic radiation force and acoustic flow in the standing wave field was analyzed,the motion characteristics of particles of different sizes under the action of the two were compared,and the appropriate particle size was given based on the simulation results.It was also proved that the finite element method is effective in solving the coupling problem of multiple physical fields.(2)The focusing property of particles in asymmetric curved channels was studied:A lattice boltzmann model of asymmetric curved flow channel was established to analyze the complex flow field distribution and the secondary flow distribution of cross section in the flow channel structure.Based on the discrete phase model,the focusing characteristics of particles of different sizes were simulated,and the relationship between particle focusing mechanism and particle diameter was discussed.The simulation results show that the particle retention is due to unreasonable structure and its influence on the success rate of particle sorting was analyzed.It was also proved that the lattice boltzmann method is effective in solving micro-scale and complex flow fields.(3)The deformability of particles in dielectrophoretic separation chips under the interaction of multiple physical fields was studied:The FEM-LBM model of dielectrophoretic separation chip was established,and the electric field,flow field and particle motion characteristics in the chip were analyzed.The particle deformation was discussed and the velocity and voltage conditions of particle rupture were obtained.Combining the statistical knowledge and simulation results,the flow channel structure was optimized,and the empirical model of particle safety parameter and the setting of various external parameters was established to provide reference for the design optimization of dielectrophoresis sorting chip.