Control and improvement of jet stability by monitoring liquid meniscus in electrospray and electrohydrodynamic jet

• Introduce a method for feedback control of the applied voltage.
• Improve the stability and uniformity of electrohydrodynamic jetting or electrospray.
• Control algorithm based on analysis of meniscus morphology.
• Reduce jet start-up time for onset of jetting.

Electrospray and electrohydrodynamic (EHD) jet have been paid much attention to produce fine droplets or particles. However, although applying a constant voltage, meniscus fluctuation may occur because of the variation in electric field. There are various reasons for the change in electric field such as distance between a nozzle to a substrate, wetting condition, pressure drop, and liquid vaporization. The fluctuation of the meniscus during jetting may cause unstable jetting and spray, which results in non-uniform patterning or coating. To tackle this problem, this paper introduces an advanced control of applied voltage that keeps the meniscus stable. An image processing method called meniscus characterization is used to provide information about the meniscus shape to a controller as a feedback signal. In addition, this meniscus information is also used to evaluate an optimal voltage that is applied to the nozzle to improve the startup time in the spray and EHD ejection. The experiment results show that the shape of meniscus is stably maintained, the jetting and the electrospray also become stable and the jet startup time is reduced.