Research On Droplet Sorting Based On Microfluidic Chip

The droplet microfluidic technology is a technology in which discrete droplets are formed by shearing incompatible fluids in a microchannel,and the droplets are manipulated.Compared with traditional microfluidic technologies,droplet microfluidic technology has the advantages of low sample consumption,no cross-contamination,fast mixing speed,strong anti-interference ability and so on.It has been widely used in protein crystallization,single cell analysis,microspheres.and nanoparticle preparation,PCR reaction and many other fields.However,the generation of droplets and the capture of cells are a random process of Poisson distribution,and it is impossible to directly form droplets of uniform size or one-to-one capture of cells.Therefore,droplet sorting based on precise size and cell capture conditions become the key to research.The droplet sorting is achieved by comparing the differences between the droplets,such as the size of the droplets,the substances contained in the droplets,etc.,in order to extract high-purity target droplets from a large number of droplets.Droplet sorting can be divided into active sorting and passive sorting.Active sorting uses external forces such as magnetic fields,electric fields,and sound waves to achieve sorting,but the sorting effect cannot have the characteristics of high purity,high efficiency,and biocompatibility at the same time.Passive sorting uses micro-channel structure,gravity,etc.to realize sorting.Although the biocompatibility is better,the purity or sorting efficiency is relatively insufficient.This thesis provides a new droplet sorting method,which uses a field programmable gate array(FPGA)to quickly calculate the size of the droplet or the cell size in the droplet through image processing algorithms to determine the target droplet.This method has the characteristics of label-free,high purity and good sensitivity.The main research contents of this thesis are as follows:(1)A test platform based on a microfluidic chip and FPGA is constructed.The platform is composed of a microscope,a high-speed camera,an FPGA development board,a display screen,a constant pressure pump,etc.,which can realize image acquisition and processing and droplet analysis and can provide power for droplet sorting.(2)Based on this platform,a microfluidic chip for droplet sorting is designed,and then COMSOL simulation is performed on the microfluidic chip,which verifies that the microfluidic chip can produce droplets normally and can sort different types of droplets.Based on the simulation,the rationality of the chip design was verified and the optimized size of the microfluidic chip was determined.(3)Based on the simulation results,a microfluidic chip is fabricated using photolithography and PDMS technology.At the same time,high-speed images are obtained based on the microfluidic chip,and an FPGA-based image analysis algorithm is designed to obtain the size of the droplet or the single cell in the droplet,and determine the target droplet.(4)Based on the microfluidic chip and image analysis algorithm,This subject obtained droplets of precise size,with a sorting efficiency of 87.1%;at the same time,This subject conducted a single cell capture experiment based on droplets to accurately sort the droplets of captured single cells.The sorting efficiency can reach 86.8%,and the purity can reach 88.3%.In summary,This subject verified the feasibility of the sorting platform and provided a label-free,high-purity droplet sorting method based on FPGA.