Development of a drop-on-demand droplet generator for one-drop-fill technology

This paper presents the design, fabrication and tests of a piezoelectric-type droplet generator, which can be used for on-line liquid dispensing system. The principle is to actuate a disk-type PZT by a function generator to push the liquid out of the droplet generator and form a near-spherical droplet due to surface tension. A light-emitting diode (LED) is simultaneously triggered using the stroboscopic technique. In situ recording of the droplet formation is achieved by a CCD camera to measure the droplet dimension by image processing methods. The influence of the process parameters on the droplet quality is also studied. For different liquids the drive conditions shall be adjusted in order to obtain the optimum droplet formation. An application to the one-drop-fill (ODF) technology of liquid crystal displays (LCD) was carried out in order to control the droplet sizes and the repeatability of the quantity.