Research Of Micro Piezoelectric Droplet Distribution And Image Monitoring Experimental Platform

Micro droplet ejection technology is a precision dispensing technology, and it has many advantages, such as non-contact, high-efficiency, less material waste. With the in-depth research on micro droplet technology, droplet distribution has broad applications in electronic packaging, MEMS, micro-optics manufacturing and biomanufacturing engineering and other fields, and it puts forward requirements of high frequency, micro droplets and precise control to micro droplets technology. Micro droplet distribution speed, size, and direction is the main factor affecting the quality of the distribution, so it is very necessary to monitor these parameters above. Aiming at the present stage domestic and foreign research on the distribution of droplets and droplet monitoring, this paper designed a set of piezoelectric micro droplet distribution system, which will achieve droplet distribution with high frequency, micro droplets and stable and controllable. Also the system will achieve effectively image monitoring to the distribution parameters such as speed, size, direction deflection of the droplet.Firstly, this paper takes theoretical analysis of piezoelectric droplet distribution process, based on the distribution principle of the piezoelectric nozzle. We use Gambit and FLUENT to carry out modeling and simulation. Through modeling, meshing, zoning, model selection, boundary conditions, UDF function and a series of simulation processes, we get the droplet distribution process is elongated by four stages, including the liquid column, the liquid column necking, fracture shaping, droplet ejection. Then we use simulation to explore the influence of driving waveform parameters, pressure, driving speed, fluid viscosity on the speed, size, droplet formation time and other parameters of the droplet distribution process, providing foundation for the set-up of droplet distribution system.Then, the droplet distribution system is constructed according to the simulation results. The designing principles of pressure control module is to provide a back pressure and to ensure that the liquid in the nozzle at a reasonable injection location. Piezoelectric driving module generates waveforms for droplet distribution through wave generation and wave magnification, then realize distribution. Image acquisition module includes a CCD, magnifying lens and LED lights, which ensure that its work in the brightness adjustable strobe environment and effectively collect droplets ’ image. Experimental platform can adjust the mutual position of nozzle, LED and CCD, to ensure the imaging monitoring after the distribution of droplets.Next, the droplet monitoring system consists of image acquisition and control systems and image processing and analysis system. Image acquisition collects clear images of droplets through the principle of stroboscopic and delay, Lab VIEW software programming, hardware debugging. In image processing, image processing algorithm is designed and each function of the algorithm is completed programming in Lab VIEW to complete the image processing and analysis tasks. We achieve measuring the size, speed, direction and other parameters using the monitoring system built on the success of the process of droplet dispensing droplet velocity, volume, and to achieve the deflection of real-time monitoring, and judge the quality of the distribution of droplets according to certain indicators.Finally, we use the droplet dispensing system designed to carry out experimental analysis. Distribution Experiment is carried out using ethanol, water and glycerol liquid. We achieve the distribution of these liquids by adjusting the parameters of pressure, voltage amplitude, etc. And we monitor the parameters of the distribution process to prove the stability of micro-droplet dispensing. We then use the droplet distribution system to achieve stable distribution from 100 Hz to 5000 Hz. And explore the influence of pressure, the driving waveform parameters, voltage, viscosity of the liquid and other parameters of droplet dispensing process, come to the discipline of distribution and summarize the control method of droplet distribution. Finally, the experimental results are summarized and the reasons and ways to avoid satellite droplets are given.