Study On Particle Capture And Separation Technology Of Sheathless Flow Microfilter Array Based On Dielectrophoresis

With the progress of micro-nano processing technology,the application direction of particle separation based on microfluidic chip is developing rapidly.In the particle separation scheme,the dielectrophoresis separation technology has become a research hotspot because of its advantages of free marking,non-invasion,high tunability and little damage to cells.Particle sorting and particle capture,as important means of studying single particle,are widely used in chemistry,life science and other fields.Traditional dielectrophoretic sorting chips all adopt the sheath flow to focus,but this scheme will dilute the sample,reduce the actual sample flux,and add additional flow channel design and external detection equipment,which hinders the development of portable and disposable chips.In this study,the dielectrophoresis separation method and the focusing scheme design of the non-sheath flow filter array were combined,the particle diameter and its own dielectric properties were used to achieve the particle capture and separation,and the microfluidic separation chip based on the microfiltration array and the dielectrophoretic force was prepared.The main research contents of this paper are as follows:Initially,the principle of fluid dynamics and dielectrophoresis is introduced in detail.According to the formula of dipole moment of particles,the formula of dielectrophoretic force was derived,the factors affecting the dielectrophoretic force and direction were analyzed,and the main forces on particles in microfluids were determined.The dielectric frequency response of silica particles and polystyrene pellets was analyzed by Matlab.On top of that,the structure of microfiltration array and microelectrode was designed and optimized by simulation analysis,and the deformation degree and focusing effect of microfiltration array were analyzed under the flow rate of 8mm/s-28mm/s.According to the structural characteristics of microfiltration array and microelectrode,the microfiltration array mold was prepared by photolithography and deep silicon etching,and the PDMS chip channel was prepared by film pouring.Microelectrodes were prepared by photolithography and wet etching.The PDMS channel and the microelectrode were treated by oxygen and other particle surface treatment.Finally,a microfluidic chip particle sorting platform was built to complete the sample solution configuration of different particles.According to the simulation results of Matlab,the critical frequency of silicon dioxide and polystyrene pellets was tested with a planar electrode.The capture and focusing effects of the microfiltration array were tested,and the capture efficiency of polystyrene pellets(20um)reached 81% when the flow rate was 14.4ul /min.The polystyrene pellet(diameter 20um)solution was mixed with two kinds of silica particles with diameters of 4um and 20 um respectively.In the separation experiments with different diameters,the collection efficiency of polystyrene pellet was more than 99% and the separation purity was 67.5%.The collection efficiency of silicon dioxide was more than 95% and the separation purity was more than 99%.In the experiment with the same diameter,the collection efficiency of polystyrene pellets is more than 99%,the separation purity is greater than 95.3%,the collection efficiency of silica is greater than 95%,the separation purity is greater than 98.9%.