| Droplet forming technology is a process of producing a single droplet through the external conditions and the droplet falls on the substrate to form a layer of film or three-dimensional structure.Droplet jetting technology has been preliminary applied in the construction of a variety of biological tissue structure,electronic components.In the future,it will be more widely used in the medical field of artificial tissues and organs and flexible electronic device manufacturing industry.The stability of droplet produced by droplet injection technology is a guarantee of high precision of droplet spray forming.The process of the qualified droplets falls on the substrate relate to the frequency of micro droplet nozzle and the print quality.Therefor,in this paper,the droplet forming technology is divided into two processes: droplet formation and droplet spreading.The following work has been done in this paper:(1)The paper described the theoretical basis of droplet jetting process and analyzed the influence of rheological properties on droplet formation.The whole process of droplet formation was simulated and analyzed by simulation software.The paper established a mathmatical model of the jet nozzle and obtained the mainly factors that affect the nozzle flow by the model analysis.(2)A micro droplet experimental platform was built.The paper introduced hardware composition and main functions of the system.And each module of the system is analyzed and introduced in detail.(3)The process of droplet forming is mainly researched by experimental and comparison based on the experimental platform.When the nozzle structure is the same,the voltage drive is the main factor affecting the droplet formation.The paper The analyzed the effect of pulse amplitude and pulse width on droplet forming through comparative analysis of distilled water with low viscosity and sodium alginate solution with viscosity.The phase diagram of pulse amplitude and pulse width for solution in low,medium and high viscosity is plotted by a large number of experiments,which provides a reference basis for the selection of voltage amplitude and pulse width of different solutions.Then it analyzed the causes of some jet defects in the experiment.(4)Mathematical modeling,simulation and experiment are carried out for the spreading process of sticky micro droplet deposition.Firstly,the mathematical model of droplet dropdeposition process was built.The main parameters influencing the spreading effect are dropping speed and contact angle.Then the whole spreading process is simulated by FLUENT software,and the simulation results and theoretical values are less than 10%.Through the simulation model,the reasons for the involvement of the bubble and the sputtering are also analyzed.Finally,the experiment platform was built with sodium alginate solution for droplet spreading,and the front theory and simulation model were verified.The results of this study provide a theoretical basis for the selection of drop drop velocity and contact angle in micro droplet deposition. |
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