Ink formulation in direct ink writing of ceramics: A meta-analysis

Direct ink writing (DIW), or robocasting, is emerging as a key additive manufacturing technique for ceramic materials. Nevertheless, controlling ink rheology, finding optimal ink properties for printability, and optimising final mechanical performance have consistently posed major challenges. This review addresses these critical aspects of ceramic DIW through a meta-analysis. It encompasses rheological data from various ceramic inks and reviews methods for tuning ink properties to improve printability. The collected rheological properties are integrated into various printability criteria and models, leading to the proposal of an empirical criterion based on two key rheological parameters. Furthermore, the mechanical properties of both dense and porous ceramic components are discussed, revealing their correlations with rheology and processing defects. The objective of this comprehensive work is to serve as a valuable toolkit and guideline, providing researchers with the necessary insights to develop superior ink formulations and enhance the mechanical performance of robocasted ceramic components.