Numerical analysis of electrohydrodynamic jet printing under constant and step change of electric voltages

Electrohydrodynamic (EHD) jet printing is a highly effective technique for micro/nanoscale three-dimensional manufacturing. However, due to the complicated electrohydrodynamic mechanisms behind liquid deformation and jet emission, the printing process with remarkable droplet consistency and excellent controllability is still under investigation. In this work, a numerical analysis is conducted on EHD jet printing under constant and step change of electric voltages. We first examine constant-voltage-based pulsating EHD jet printing and explain the impacts of voltage on the regimes, deposited droplet volumes, and durations of the three key printing stages, namely cone formation, jetting, and jet/meniscus retraction and oscillation. After that, we carry out a comprehensive investigation on EHD jet printing under various step changes of voltages, while focusing on the jet behaviors at the voltage switch and after detaching from the Taylor cone. With the assistance of the electric field distribution, interface charge density, velocity fields, and very clear liquid motion images obtained from the numerical data, we fully inspect the pulsed printing processes and elucidate the influences of the pulse time, bias voltage, and peak voltage on the printing behaviors, durations of the three printing stages, and deposited droplet volumes. Finally, based on the obtained results, we make a comparison of the printing outcomes between these two techniques. The findings discovered in this work can be used for advancing the understanding and controlling methods of this complicated but very useful manufacturing technology.