Abstract
A colloidal solution is a mixture of small insoluble solid particles with a fluid, widely used as ink solutions in inkjet-based 3-dimensional (3D) printing technology. During the printing process, the liquid solvent is removed via subsequent drying processes, such as evaporation, with only solid particles deposited on the substrate. The printed products’ quality and mechanical properties can be harmed when the particle distribution is non-uniform due to the internal flows occurring in a droplet during evaporation. To address this issue, a freezing sublimation-based printing method was developed in recent year to minimize internal flow-related particle motions during the drying process, which can improve the quality of printing. While the colloidal particles were found to be distributed much more uniformly on substrates using the novel freezing sublimation-based method, it was found that colloidal particles could form 3D porous structures on substrates after the solvent was sublimated. In this paper, an experimental study was conducted to evaluate the particle deposition patterns of 15% (w/v) Pearlitol 100 SD Mannitol water solution droplets under different sublimation conditions. The porous structures formed on substrates after sublimation were visualized using microscopy imaging technology. The results obtained from this study showed that pores formed in printed structures are directly related to the escaping gaseous phase from frozen droplets during sublimation. Smaller and fewer pores are formed when the heating rate during sublimation is slower. Therefore, a slow sublimation process is recommended for the freezing sublimation-based inkjet 3D printing method for producing better quality and higher resolution 3D products.
