Study On The Mechanism And Method Of Linear Injection Of Micro Reagents

Reagent treatment technology is one of the most commonly used experimental means in life science experiments.In the experimental operations in biology,chemistry,medicine and other fields,micro reagents often need to be absorbed,distributed,transferred and other operations.In recent years,with the development of these fields,more and more kinds of liquids are involved in the research,and the volume of liquids required in the experiment is getting smaller and smaller.In the process of automatic micro-liquid dispensing,the demand for liquid dispensing speed and accuracy is getting higher and higher.It can be seen that these developments urgently require the dispensing of micro liquid to be faster,more trace,more accurate,and more applicable.Among many micro liquid dispensing methods,the linear injection dispensing technology based on syringe pump is the most commonly used micro-liquid dispensing methods at present,because of the advantages of simple structure,easy control,reliable operation and high precision.The principle of the method is to use the motor to drive the piston to do linear motion to realize the automatic absorption and discharge of a certain amount of liquid.In the actual use of linear injection dispensing system,the setting of system parameters has a great influence on the dispensing process of micro liquid.When the system parameters are not set properly,the reagent may appear adhesion,bubble,breakage,residue,satellite droplets and other phenomena after leaving the sample needle,and rebound,breakage and residue may appear after collision with the wall of reaction cup.The occurrence of these phenomena may affect the final amount of reagent liquid,which is not ideal dispensing effect,and the dispensing accuracy of micro-liquid dispensing system may not be guaranteed.Aiming at the above problems,this thesis designs a micro-liquid dispensing system based on syringe pump and the equivalent model of the dispensing system and the simulation model of reagent detachment and collision process based on the system are built.The method of numerical simulation combined with experiment is used to study the influence of different system parameters on the liquid behavior characteristics in the dispensing process.The obtained laws provide theoretical guidance for obtaining ideal dispensing results in subsequent research and applications,and design and optimization of micro-liquid dispensing systems.In this thesis,a micro-liquid dispensing system based on syringe pump is designed.According to the bond-graph theory,the equivalent model of the dispensing system is established by lumped-parameter method,and the state equation of the system is obtained.According to the state equation of the system,the MATLAB simulation program diagram is established in Simulink,and then the influence of key system parameters on the dispensing process is analyzed and simulated by focusing on pipeline pressure and outlet flow.The results provided theoretical guidance for the design of the micro-liquid dispensing system and the setting of system parameters.Secondly,the micro-liquid dispensing process based on syringe pump is studied by numerical simulation.The CFD simulation software Fluent is used to build the simulation model of micro-liquid dispensing process.Considering the existence of the isolated air column in the simulation model,the influence of various system parameters,such as air volume(length),reagent volume(length),pipeline diameter,surface tension,viscosity,inlet velocity,etc.on the morphology of liquid is analyzed comprehensively by simulating the morphology change of liquid in the whole process from flowing in the pipeline to leaving the sample needle.The parameter range that could achieve the normal dispensing of liquid is obtained.Next,the collision process of micro liquid with reaction cup wall after leaving the needle tube is studied by numerical simulation.Based on the CFD simulation software Fluent,a simulation model of the micro-liquid collision process is constructed.Starting from the characteristics of the reagent itself and the surface characteristics of the reaction cup wall,the parameters of the reagent volume,dispensing speed,viscosity,surface tension,contact angle and wall angle are studied.The influence law of the liquid behavior characteristics during the collision,the conditions and causes of the phenomenon appearing in the analysis process,and the influence law of different parameters are obtained,so as to optimize and guide the setting of system parameters.Finally,a set of experimental platform for micro-liquid dispensing system based on syringe pump is built.Validation experiments are carried out based on the laws obtained from theoretical research,which include the validation of the system model and the visual monitoring of the process of reagent separation and collision.Under the guidance of the above theoretical research,experiments on reagent dispensing accuracy and repeatability are carried out,thus verifying the feasibility and reliability of the research results of the micro-liquid dispensing technology based on syringe pump in this thesis.