Modeling and analysis of jetting behavior of surface charge-induced electrohydrodynamic printing

Electrohydrodynamic (EHD) printing enables large-area, ultra-high-resolution manufacturing across a broad range of ink viscosities, but inevitably encounters difficulties when printing on electrically insulating three-dimensional substrates due to unpredictable electric field and surface residual charges. To overcome these obstacles, a novel approach called plasma-induced electrohydrodynamic (PiE) printing has been proposed. PiE printing employs plasma to directly create a controllable local charge region directly on substrate surfaces, which triggers EHD ink ejection and mitigates the effect of residual charges. However, the underlying mechanisms of the jetting behavior with respect to printing parameters, such as the charge-induced electric field, remain unexplored. Here, we conduct a numerical investigation, based on the Taylor-Melcher leaky dielectric model and the level set method, on the jetting behavior of substrate surface charge-induced EHD printing. We first introduce the dynamics behavior throughout the entire printing process. Then, we carry out a comprehensive investigation on surface charge-induced EHD printing under four crucial parameters: the amount of preset surface charge, the radius of preset surface charge, the duration of preset surface charge, and liquid electrical conductivity. By analyzing the induced electric field, induced charge density, fluid velocity, jet diameters, and deposited droplet sizes obtained from the numerical results, we elucidate the influence of these parameters on the dynamic behavior, durations of jetting process, and printing quality. These findings offer valuable insights into surface charge-induced EHD jetting, advancing the understanding and optimization methods for this useful micro-/nano-manufacturing technology.