A method is demonstrated for studying hydrodynamic effects in pulsed electrohydrodynamic (EHD) jetting, for the drop-on-demand printing of small droplets. The transient behaviour of pulsed EHD jets and the deposition of liquid on to a substrate were investigated by using an ultra-high
speed camera (Shimadzu HPV-1) with a Newtonian aqueous liquid (water-glycerol). Time-resolved images of jets induced by two consecutive voltage pulses, with different time delays, were captured. Image analysis was used to determine the jet length, meniscus radius at the nozzle, and deposit
volume in each case and revealed that the behaviour of an EHD jet depends strongly on the delay time after a previous ejection event. The effect originates in the time taken for the meniscus shape and position to recover to their equilibrium values and plays a critical role in the design of
printing strategies for EHD drop-on-demand applications. It is possible that the maximum printing frequency achievable by pulsed EHD jetting can be increased by optimizing the drive waveform in order to accelerate recovery of the meniscus position.