Research Of Microfluidic Impact Printing Technology And Its Application

In recent years microdroplet technology has emerged as a promising tool for modern biochemical analysis experiments and materials synthesis.As a novel microreactor,microdroplet has several highlights,including miniaturization,compartmentalization,and parallelization.At present,microdroplets are mainly generated by emulsification method,micro:fluidic method and printing method.Benefiting from flexible handling of droplet size,number,generation rate,and dispensing position,drop-on-demand printing technology are widely used in a variety of fields such as biological tissue printing,drug screening,chemical crystallization,and gene analysis.Microfluidic impact printing technology,as a novel drop-on-demand printing technology,combining the characteristics of microfluidic technology and traditional printing technology,generates microdroplets under the action of external energy implemented on microfluidic cartridge structures.The modular design enables the interchangeablity of microfluidic cartridges,increasing handling flexibility and applicability when printing droplets.In addition,thanks to the low-cost and disposable propery of microfluidic cartridges,cross-contamination when printing multiple reagents is no longer a critical issue.In this dissertation,we devote to research on the working principle,structural design,system construction and practical application of microfluidic impact printing technology.(1)The theoretical research of microfluidic impact printing technology and the construction of printing system.A mathematical model of microfluidic impact printing was established,revealing the effect of actuator operating parameters and cartridge structure parameters on droplet size.The finite element method was used to simulate the process of droplets generation.A multi-channel microfluidic impact printing system based on piezoelectric drive was built and the performance of the system was characterized.The fabrication process of microfluidic cartridge was studied.The surface of the nozzle of the cartridge was super-hydrophobic treated by the femtosecond laser direct writing technology to avoid liquid adhesion,which increase the system stability and printing frequency from 65 Hz to 125 Hz.(2)Design and optimization of flow resistance characteristics of microfluidic cartridges.According to the mathematical model and verified by experiment,the flow resistance of the microchannel in the microfluidic impact printing system is an important factor affecting the printing performance of the droplets.The effects of microchannel flow resistance ratios on droplet volume and ejection velocity were studied,and the optimal flow resistance ratio range was determined.A converging channel with asymmetric flow resistance is introduced into the microfluidic cartridge,which reduces the air aspiration volume of 40%during printing.The printable droplet volume range extends from 6.5?10.8 nL to 6.1?12.5 nL,and the maximum print rate is also increased from 65 Hz to 90 Hz.(3)Research on portable digital droplet dispensing technology.Combine microfluidic impact printing technology with traditional pipetting technology,a novel digital droplet dispensing technology was proposed.The technology uses a single nanoliter droplet as the smallest unit,the target volume is calculated by multiplying the unit volume of ejected droplets and the number of ejections.Compared with the traditional pipetting technology,the droplet dispensing technology has nano-scaled resolution with an error of less than 2.3%.With high-resolution,high-precision liquid handling capabilities,digital droplet dispensing technology delivers outstanding performance in practical applications such as low-concentration solution dilution and biochemical analysis.The creative point of this dissertation is to comprehensive study the working principle of microfluidic impact printing technology,and establish a mathematical and finite element simulation model to predict the droplet volume under different parameters.The influence of flow resistance on droplet printing performance was analyzed.The cartridge was optimized by introducing a converging channel to improve the stability of the system and increase the printing rate.A piezoelectric-driven 4-channel microfluidic impact printing system was built,and the robustness of nanofluidic printing and the substitability of microfluidic chip were proved.The fabrication process of the microfluidic chip is perfected,and the super-hydrophobic treatment of the nozzle surface was preposed to achieve high-precision,high-resolution droplet printing.A digital droplet dispensing technology based on microfluidic impact printing technology and traditional pipetting technology was proposed to achieve high-precision portable distribution of nanoliter volume liquids.