Study On Micro Dispensing Method For A Valvecontrolled Pneumatic Jetting System

In the field of life sciences,various types of test activities,such as protein crystallization,gene sequencing,new drug manufacturing,PCR,etc.,often require analysis of various biological reagents.Related research activities mainly operate on liquid in the range of 1 00mPa.s,and the volume of liquid that needs to be dispensed has reached the level of nL or pL,which urgently requires the micro-liquid distribution technology to be faster,smaller,more precise,and applicable.Among the many small amount of liquid dispensing methods,the valve-controlled pneumatic jetting method uses air pressure to drive the droplets out the nozzle at high speed,and has the characteristics of small dispensing volume,high dispensing accuracy,and fast operation speed.However,the method is difficult to control,the system is complicated,and the system parameters haves a great impact on the dispensing processing of the micro liquid.When the system parameters are set improperly,it may cause the phenomenon of dispensing failure,which in turn will affect the accuracy of the micro liquid.Therefore,how to control the dispensing volume and repeat dispensing accuracy of the micro liquid is very meaningful.In response to the above problems,the paper established a valve-controlled micro liquid jetting system.The CFD simulation model of the micro liquid dispensing process and the bond graph of the micro jetting system were constructed,and the influence of different system parameters on the behavior of droplets in the dispensing process was studied by using numerical simulation combined with experiments.Then use the LabVIEW particle analysis module to extract the size information of the droplets during the dispensing process,and obtain the theoretically calculated droplet volume,which provides theoretical guidance for the setting of system parameters and the selection of reagent characteristics.The research results ensure that the micro liquid jetting system cab distribute droplets with faster speed,smaller volume and higher precision in the field of life sciences.In order to ensure that droplets with different viscosities can be stably separated from the end of the nozzle,the formation and separation process of micro droplets was studied in this paper.Firstly,the simulation model of the micro liquid dispensing process was constructed based on the CFD simulation software Fluent Then change the driving pressure,liquid viscosity,surface tension,nozzle diameter and other system parameters in the micro liquid dispensing jetting,and convert these system parameters into dimensionless parameters to study the combine effect of the droplets shape and volume,as well as the jetting interval between droplets Finally,the conditions that the droplets can be separated from the nozzle to achieve ejection are given,so as to provide guidance for subsequent experimental researchThen,according to the structure and working principle of the valve-controlled pneumatic micro liquid jetting system,and based on the bond graph theory,the bong graph model of the micro jetting system was established by the lumped parameter method,and the state equation of the system was obtained.Then the simulation is caried out through the Simulink module of Matlab software,and on this basis,the influence law of the system parameters on the jetting velocity and dispensing volume of the micro droplets is obtained.Then,the validity of the bond graph model of the micro liquid jetting system is verified through experiments,and this research results provide theoretical guidance for the design of the micro liquid dispensing system and the optimization of system parameters.In the next step,in the dispensing process of micro liquid,the paper built a micro jetting volume visual monitoring platform.Using an industrial camera with a strobe light,a series of droplet pictures ae collected through image acquisition software Vimba Viewer.Then based on the Lab VIEW program,perform particle analysis on the collected droplet image to obtain the size of the droplet.An explored the impact of changing system parameters on the droplet flying speed Finally,the droplet ejection experiment verified the validity of the theoretical calculation of droplet volume.Finally,based on the above.research,the next design a valve-controlled pneumatic jetting system,and builds an experimental platform including a micro liquid jetting valve,the micro liquid jetting valve driving module,the pneumatic driving module,and the volume monitoring feedback module.Based on this platform,experiments on the repeatability and distribution accuracy of micro liquid materials of different viscosities.Experimental results show that the repetition accuracy of the micro liquid system is better than 8%(CV)and the distribution accuracy is controlled within ±5%.The experimental results are consistent with the simulation results to verify the feasibility of the system in the field of life sciences.