Deposition pattern of colloidal particles in electrohydrodynamic (EHD) jet printing

Abstract

In this study, the colloidal suspensions containing silica nanoparticles were deposited by electrohydrodynamic (EHD) jet prninting and the line-patterns were systematically observed. EHD jet printing is a method to eject the fluid and form line-patterns by applying high DC voltage similar to ink-jet printing that applies pressure to generate droplets. To make the line-pattern with a uniform shape, the stability of EHD jetting should be guaranteed. It depends on the operating conditions (DC voltage, flow rate, and the distance between the nozzle and the substrate) and the properties of the suspension (viscosity, surface tension, dielectric constant, and conductivity). Among the material properties, we focused on the effect of viscosity on the stability of jetting by controlling the concentration of poly(vinyl alcohol) (PVA). For the wide range of concentration, we observed the effect of operating conditions and the concentration of PVA on the surface profile of line-patterns by using optical microscope, scanning electron microscope (SEM), and profilometer. From these observations, we could find a change of the microstructure of silica/PVA and its effect on the surface profile of line-patterns. Consequently, the uniformity of the surface profile was decreased with the increase of PVA concentration. Conclusively, we could control the uniformity of the deposited pattern shape by changing the polymer concentration.