Effect of gravity on electrohydrodynamic (EHD) printing of silver nanoparticle and polycaprolactone based inks

Abstract

Additive manufacturing is a promising technology to realize in-space manufacturing and long-duration manned space missions. Electrohydrodynamic (EHD) printing is an emerging additive manufacturing technology that offers high resolution and compatibility with a wide range of materials. A unique feature of EHD printing is that it does not rely on gravity for printing; instead, it uses a high electric field to induce fluid flows from micro capillary nozzles. Although gravity is not a determining factor in EHD printing, it can influence the printing process and performance. To make EHD printing a viable technology adaptable to different printing orientations and gravity magnitudes, it is essential to understand the effect of gravity on EHD printing. In this article, the effect of gravity on EHD printing of silver nanoparticle (AgNP) based ink and polycaprolactone dissolved in glacial acetic acid (PCL-GAA) ink were studied. Three printing orientations denoted as traditional, horizontal, and vertical setups were constructed in which the angle between the jetting direction and gravity direction were maintained at 0°, 90°, and 180°, respectively. The influence of gravity on critical voltage and printing resolution were studied through theoretical, experimental, and computational analyses. Results indicate that gravity has a noticeable impact on critical voltage and printing resolution. Compared with the traditional setup, the critical voltages are 5% and 10–25% higher, and the dimensions of printed patterns are 6–40% and 18–350% larger in the horizontal and vertical setups, respectively.