Numerical investigation of high-frequency pulsating electrohydrodynamic jet at low electric Bond numbers

Abstract

Electrohydrodynamic jet printing is a highly promising technology for the fabrication of three-dimensional micro/nanoscopic structures, but the advancement of this technology is hindered by the insufficient understanding of many aspects of its mechanisms. Here we conduct a numerical investigation on high-frequency (∼1 kHz) pulsating electrohydrodynamic jet at low electric Bond numbers ( B o e = 0.15–0.7). By analyzing the entire jetting process using the voltage distribution, electric charge density, and flow field obtained from the numerical results, we overcome the limitations of experimental approach and demonstrate the influences of electric voltage ( Φ), nozzle-to-substrate distance ( H), and liquid surface tension coefficient ( γ) on the dynamic behaviors and durations of the three jetting stages: (1) cone formation, (2) jetting, and (3) meniscus oscillation. Furthermore, as a measure of the relative significance of the electric force to the surface tension force, the impacts of B o e on the jetting process are also examined. Results show that some critical aspects of the pulsating jetting process are closely related to B o e: (1) the transitional values of B o e between the four observed jetting regimes on the variations of Φ, H, and γ apply to all three parameters; (2) the nondimensionalized Taylor cone length scales with B o e according to a power law; (3) the jetting processes that have similar B o e collapse onto a universal profile. These new findings of pulsating electrohydrodynamic jet provide a useful supplement to the currently inadequate comprehension of the complicated electrohydrodynamic jet printing process.