Simulation And Experimental Study On Piezoelectric Diaphragm-driven Microdroplet Jetting Technology

As an accurate and efficient printing technology, the ink-jet printingtechnology has gained great success in commercialization of products. Therapid development of this technology shows that a precisely controlledmicrodroplets generation technology has great application value. With thedeepening of its application, microdroplets generation technology hasexpanded to microelectronics packaging and micro-optics manufacturingtechnical field from the original inkjet printing. Meanwhile, the kinds ofmaterial are not limited to thermal ink, but the high viscosity fluid materialssuch as lubricant, photoresist or molten metal used in industrial fiels.Microdroplet jetting technology is a digital controlled micron dropletsgeneration and dispensing technology. In this thesis, a piezoelectricactuated diaphragm-driven microdroplet jetting technology is presented.This technology uses multilayer piezoelectric ceramic attached a push rodto drive the diaphragm and squeeze the liquid material for drop-on-demandjetting. We can precisely controlled the microjet process and get smallerdroplets at high frequency by piezoelectric ceramic control signal. Themicrojetting device can effectively prevent the heat conduction frommaterial to piezoelectric ceramic by using the push rod to drive thediaphragm instead of the piezoelectric sheet direct drive.This thesis focuses on the research of piezoelectric diaphragm-drivenmicro-droplet jetting technology and the design of the microjetting device.Firstly, the primary principle of the microdroplet jetting technology isintroduced and theoretical analysis be made to established themathematical model of the microjetting system. Two-dimensionalaxisymmetric simulation models are presented to predict the fluid interface during the microjet process using CFD software and VOFmethod. We analyzed the effect of parameters on the droplet ejectioncharacteristics based simulations, such as droplet diameter and dropletejection velocity. The empirical formulas and criteria for microdropletformation are concluded based on the analysis data.According to the results of simulation analysis and theoretical study,we carried out the the design of the microdroplet jetting device, includingdriving parameters and structure design. And then develop a piezoelectricactuated diaphragm-driven microdroplet jetting device.In order to conduct the microjetting experiments, the piezoelectricdiaphragm-driven micro-droplet jetting experiment system has been madeup, which consists of three sub-systems besides microdroplet jettingdevice:motion control system, temperature control system, measuring&image acquisition system.Finally, we conduct the microjetting experiments using liquid materialwith viscosity ranging from0cP to150cP, including water, mixture ofwater and glycerol and liquid paraffin. We have obtain microdroplets ofdifferent volumes, whose size variation less than1.5%of diameter. At thesame time, we change the control parameters to do the microjettingexperiments, like backpressure, the temperature of material, operatingfrequency. According to the experimental results, we analyzed the effect ofthese parameters on the microdroplets. The experiments demonstrate thatthis microjetting technology has a good performance on micron dropletsgeneration and dispensing. And the experimental results agree well withthe simulation results, which proves this simulation model and method iscorrect.