Single event electrospraying of water

Single event electrospraying (SEE) is a method for on-demand deposition of picoliter volumes of liquids. The steady electrospraying of water in the cone–jet mode is difficult under normal operating conditions. This paper shows that SEE can be used for water to deposit very small volumes (1 pL) and spray water in a stable pulsed cone–jet mode. The stability regime for SEE of deionized water with regard to pulse time and frequency of applied voltage was determined and was explained by the analysis of the characteristic times involved in SEE. With our unique set-up it is possible to use a pulsed cone–jet mode for a stable ejection on-demand. The pulse time for stable SEE of water is limited due to the time of formation of a space charge in between the nozzle and the counter electrode. Moreover, the maximum pulse frequency is limited to two times the natural oscillation frequency of the liquid. Additionally, the volume of liquid deposited per SEE can be calculated using a theoretical consideration of the electrohydrodynamic displacement of water inside the capillary.