Time resolved imaging of electrohydrodynamic jetting on demand induced by square pulse voltage

Electrohydrodynamic (EHD) printing is receiving much attention due to its high resolution printing capability, as well as its many advantages such as reduced manufacturing steps and non-toxic, flexible processes. However, many issues need be resolved before it can be widely used. In this work, to demonstrate EHD printing on demand, square pulse voltage signals are applied between a hole-type electrode and the nozzle supplied with working fluid from a reservoir at constant pressure. Continuous fine jet, pulsating fine jet, and pulsating droplet modes are observed depending on the voltage signal. To obtain the optimum voltage pulse duration, the change in the jetting start time is measured by varying the voltage configurations and hydrostatic pressure applied to the nozzle. Among the modes, the pulsating droplet mode is studied in detail for various voltage signals. Futhermore, the printing is demonstrated using the optimized voltage signal.