An Experimental Investigation on Colloidal Droplet Behavors in a Freezing-Based Inkjet Three-dimensional (3D) Printing Method

Inkjet-based three-dimensional (3D) printing is an additive manufacturing technology that has received much attention in recent decades. In this method, liquid droplets of ink are dripped onto a substrate. After drying, the liquid phase evaporates, but solid particles of printing materials in the ink remain and form the desired structure on the substrate. During a typical evaporation-based drying process, fluidic motions into droplets affect the distribution of solid particles. Thus, the resolution and uniformity of printed patterns are limited. In this study, we developed a novel freezing sublimation-based method to improve printing quality: the printed inkjet droplets were frozen onto the substrate. Afterward, a sublimation-based drying process removed liquids from the frozen pattern. Using this method, a rapid freezing process of inkjet droplets improves the adhesivity of printing materials on different surfaces, widening the applicable working conditions of the inkjet-based 3D printing method. In addition, a sublimation-based drying process shifts the frozen liquid phase into a gaseous phase, which minimizes the internal flow of the liquid phase during the drying process. Thus, this method significantly improved the uniformity of materials in a printed structure. In this study, we experimentally proved the concept of this proposed method and investigated the effects of printing conditions on the quality of printed patterns.