Not only direct current (DC) high voltage sources, but also multistep pulse voltage sources  and alternating current (AC) voltage sources can be used as the high voltage sources for EHDP. Espln et al.
Stainless nozzle (inner diameter = 62 [micro]m, outer diameter = 90 [micro]m) was used as the EHDP spinneret, and the distance from spinneret to the collector was 2 mm.
The injection and deposition behaviors of AC EHDP droplets were studied further to improve the control technology of microdroplet injection.
During the experimental process, the positive AC voltage amplitude [U.sub.b] was fixed at 2.8 kV, and then the negative AC voltage amplitude [U.sub.a] was varied to study the effect of applied voltage amplitude on the AC EHDP injection process.
Negative voltage generated a reverse force and the charged jet shrank back, which helped the EHDP jet break into droplets.
A higher duty cycle p led to longer charging time, larger charge density, and higher motion speed of EHDP jet, which would help the jet break up into microdroplets.