Dimensionless Analysis of the Transition from Continuous Jet Mode to Natural Pulsation in Electrohydrodynamic Jet Printing

Abstract

Electrohydrodynamic jet (e-jet) printing is a promising additive manufacturing technique that has demonstrated high-resolution fabrication capabilities. Various jetting regimes as a function of the input voltage signal have been identified and studied. In DC printing, a transition has been observed from the continuous jet to the natural pulsation mode, which precipitates less predictable outcomes on the print rate and quality of the final pattern. This phenomenon is not well understood, and its behavior is yet to be characterized. Accordingly, the natural pulsation initiation (NPI) of 15 solutions with unique viscosities and conductivities was analyzed. Dimensionless parameters referencing material properties (Ohnesorge and ratio of capillary to charge relaxation time), applied voltage (electric capillary), and induced flow rate (Weber) are implemented to analyze the dynamics of this transition. Our findings indicate that NPI is generally more prevalent in inks with higher conductivities. Additionally, less viscous inks appeared to inhibit NPI, providing a larger design space for attaining stable behavior.