Doyoung Byun

Electrospray on superhydrophobic nozzles treated with argon and oxygen plasma

We report on a simple process to fabricate electrohydrodynamic spraying devices with superhydrophobic nozzles. These devices are useful, among other things, in mass spectrometry and printing technology. The superhydrophobic nozzle is created by roughening the surface of the polyfluorotetraethylene (PTFE) by argon and oxygen plasma treatment. We have developed a polymer-based electrospray device with a flat, superhydrophobic nozzle capable of maintaining a high contact angle and stable jetting.

Efficient Control of Electrospray Emission for Colloid Microthruster with Laminated Electrodes

(Abstract) In this paper, MEMS based colloid micro-thruster, feature by MEMS fabricated nozzle with a conductive pole inside, is developed by bulk silicon processing. This paper also investigates the effect of the laminated electrodes on the efficiency and stability for forming jets from the liquid meniscus. Unlike conventional colloid microthruster, which is composed of conductive nozzle and single external extractor electrode, we offer more efficient mechanism for controllable operation based on layered electrodes and pole type nozzle. The layered electrodes allow the cone and jet formation, and acceleration of spray to be controlled by the voltage signals applied to individual electrodes. It is experimentally verified that the use of the pole type nozzle and the layered electrodes allow the stable and sustainable cone jet mode for an applied voltage as low as 800 V.

The Experimental Study of EHD Printing for Different Nozzle Shapes

The shape of nozzle cross-section plays an important role in stabilizing electrospray jet. The angle of contact line is governed based on the famous Young-Laplace equation. Compared to a round nozzle that has a constant curvature along the orifice, the square nozzle has four square corner edges and four straight edges that hold the meniscus in a different manner and is of interest in this study. By utilizing both square and round capillary nozzle, we examine the effect of nozzle shape in electrohydrodynamic jetting. The ejections were recorded with a high speed camera and analyzed to examine the jetting repeatability based on dynamic movement of meniscus. The result suggests that if the corner edges are not sharp, then its effect on repeatability is also limited.