Experimental Research On EHD Printing

The manufacturing technique of micro structure or pattern is extremely important in the micro electromechanical system (MEMS) fabrication technique. The high precision in the MEMS fabrication, the printing technique can be used in the functional material printing, macromolecule printing, bio-sample printing, package glue printing. Especially, the printing technique will have a big requirement in the fabrication of micro polymer bio-apparatus. The basic printers have been used broadly in the printing of functional material printing, macromolecule printing, bio-sample printing, et al. However, they are limited in the future applications because of self-defects. In the dissertation, a novel Drop-On-Demand (DOD) printing mechanism based on the ElectroHydroDynamics (EHD) instability is presented. Not only designing and establishing the EHD printing system, but the works focus on the investigation of the formation of jets and the influences of the experimental parameters on the droplets, such as the solution, the voltage amplitude, the printing distance, the collector surface character, and seek the optimum parameters. This paper includes five aspects listed as follows:(1) Bring forward a novel method for the high precision DOD printing technique based on the principle of EHD. Design and establish the EHD DOD printing system.(2) Observe the formation of jets on the surface of pendent drop at the outlet of the printer nozzle by optical microscope, including the Taylor cone, the different printing modes at different printing distance, such as dripping mode, cone-jetting mode. And based on the experiment results, analyze the reasons for the printing mode.(3) In the dripping mode, the experiment results show that the droplet diameters get smaller with the voltage increasing. And when the frequency increases, the droplet diameters get smaller. Also the uniformity of the droplets turns worse as the average diameters changing smaller. The droplets behave different on four kinds of collectors, such as silicon, aluminum, copper, paper. On the silicon, the droplets are the largest and most uniform. On the paper, the droplets are the smallest and the most unorderly. (4) In the cone jetting mode, the experiment results show that the droplet diameters get larger with the voltage, the solution concentration and the voltage duty cycle increasing respectively. When the frequency and the contact angle increase respectively, the droplet diameters get smaller. Also, simulate the aggradations of the droplet, and investigate the different characters of the collector surface that influent the droplets by the CFD Fluent software.(5) Analyze the intensity of electric field in EHD printing process by the ANSYS software to study the electric field distribution and calculate the electric field by numerical model.