Electrostatically-assisted direct ink writing for additive manufacturing

Abstract

Nozzle-based three-dimensional (3D) printing (additive manufacturing) technologies, which build a model by depositing and stacking materials layer-by-layer, are limited by long layer-build time resulting in low throughput. While nozzle-based printing is already arguably versatile, such sub-categories as Direct-Ink-Writing (DIW) find difficulty when printing material on rough surfaces. Recently electrohydrodynamic (EHD) elements added new features in droplet positioning but also revealed limitations in the achievable build height due to the need for a grounded substrate or embedded electrode. Here, we introduce an additional electrode added to the printhead generating an electric field (E.F.) between the above-mentioned electrode and printing nozzle. The resulting Coulomb force pulls the extruded ink in the direction of printing allowing faster translational speed, thinner trace widths, and improved deposition on rough surfaces without a decrease throughout the build height. We also developed the electrohydrodynamic theory of the proposed DIW processes. After completing DIW experiments on a translating belt with a stationary nozzle, an electric field oriented in the direction of printing was retrofitted to a DIW-based 3D printer. The integration of the electrode to the printhead allowed successful prints at the machine’s maximum speed of 500 mm/s for a documented situation in which DIW previously failed in existing literature. Similarly, successful prints were achieved on rough surfaces where the printing was impossible without the applied E.F. Along with new design opportunities, these results unlock speed restriction within nozzle-based printing while significantly expanding versatility and substrate choices. Compared to the state-of-the-art DIW processes, our electrostatically-assisted direct ink writing technology shows orders of magnitude faster direct writing speed (> 500 mm/s) and capability of printing on super-rough surfaces which were impossible before.