Study On Particle Separation Chip Based On Sheath Liquid Flow Focusing And Self-charging Droplets

The microfluidic chip is a technique for manipulating fluids on a micro-scale channel.It combines the basic functions of a biochemical laboratory onto a chip with a surface area of only a few square centimeters.It is also called a “lab on-chip”..Due to its high integration,low pollution,and low cost,microfluidic chips are widely used in many fields such as environment,biology,energy,national defense,and agriculture.Among them,the droplet microfluidic technology is a new branch developed from the field of microfluidics,and the dispersed microdroplets are regarded as independent microreactors.Because the droplets generated by the microfluidic chip are relatively uniform in size,flexible in manipulation,and have excellent thermal energy transfer,it has wide applications in drug screening,particle separation,high-throughput single-cell research,and the like.Sodium alginate is a water-soluble material that has good biocompatibility and is therefore often used in biological experiments such as drug mixing and cell fixation.In addition,the sheath flow structure can realize the neat and orderly arrangement of the micro particles or cells,and can prevent the droplets from wrapping a plurality of micro particles.Based on this,this paper will conduct droplet formation and sheath flow experiments under different conditions,and based on the droplet microfluidic technology,analyze the movement process of "self-charging" sodium alginate droplets in the electrostatic field.Design a particle separation chip based on sheath flow focusing structure and self-charging sodium alginate droplets and build related systems,which are used to screen microparticles and provide technical support for screening biological samples such as cells and viruses.The main work of this paper is as follows:(1)Processing microfluidic chips with microelectrodes and optimizing their processing technology: selecting suitable processing materials according to chip functions and related processing environments,fabricating silicon molds by photolithography,and preparing microfacies by molding After the PDMS substrate of the channel structure is completed by the plasma cleaning method,the low temperature wire is introduced into the microelectrode channel to obtain the microfluidic chip with the microelectrode structure;whether the heat treatment is effective and the recovery is fast after the bonding The hydrophobicity of the surface of the PDMS chip runner.(2)Study on the influencing factors of sodium alginate droplet formation: analyze the influence of different dispersed phase viscosity and continuous phase flow rate on droplet formation.(3)Study on the influencing factors of the sample solution width after focusing: based on the sheath liquid focusing principle and the derived formula,find out the factors that may affect the focusing width and use single factor experiments to explore their effect on the sample solution width after focusing.Influence;an orthogonal experiment was designed to find the primary and secondary factors affecting the width of the sample solution after focusing.(4)Study the charge type and charge amount of self-charging sodium alginate droplets in non-polar oil: First,design and prepare a microfluidic chip with microelectrode and flow focusing structure;By changing the direction of the electrostatic field,the type of charge carried by the self-charging droplets was investigated.According to the force of the self-charging droplets in the electrostatic field,the formula for calculating the charge amount is derived.Finally,the speed of the droplet along the direction of the electric field under different voltage conditions is measured using a high-speed camera and ImageJ image analysis software.And substituting it into the self-charging droplet charge calculation formula to calculate the charge amount of the droplet.(5)Design a microfluidic sheet for microparticle separation and build a corresponding system for microparticle separation experiments.