Drops-on-drops thick film coating by stable viscous electrostatic jets

Applying micro spray of electrostatic inkjet to thick film coating was examined experimentally. High quality coating is expected by drops-on-drops of super fine and mono-diameter droplets. At first, the jetting states of two viscous solutions were observed to determine coating parameters. Then, with those parameters examined, the possibility of thick film coating was tested. According to the increment of applied voltage, jetting mode was varied from Mode 1, dripping, to Mode 2, jetting. The most favorable condition for coating was the stable cone-jet mode in the jetting mode, where a well-oriented thread was jetted from the stable Taylor Cone at the nozzle tip and broken up into mist during flight. From the coating experiments with the selected liquid and conditions of jetting, the possibility of uniform and thick film was demonstrated by piling up the droplets several times, whose diameters were less than 10 micrometers. The alternative methods to enhance breaking up of droplets and stabilize its process were also proposed.