Advances and obstacles to unify the concept of “printability” in Ceramics Direct Ink Writing

In Additive Manufacturing, “printability” describes the ability to shape a functional 3D object from a starting material. This concept is not easy to define because it depends on several factors including material considerations (microstructure and rheological properties), as well as process parameters that cannot be evaluated by a single metric. Some printability criteria have been proposed to classify and map the rheological properties of DIW inks. However, these criteria fail to capture all the relevant rheological aspects, and to consider DIW system technical specifications, processing parameters, and final part properties, while rheological characterisation methods remain inconsistent and lack standardisation. This review tackles this gap in the field by providing an overview of literature investigating the links between rheological properties and printability for ceramics DIW. Based on recent findings, we present an overview of specific rheological tests and parameters that correlate with printing behaviour to achieve high-quality outcomes in ceramic 3D printing.