Influence of grain size and grain-size distribution on workability of granules with 3D printing

3D printing is a promising method for fabrication of scaffolds. Microporosity is one of the most important properties of scaffolds and directly influences cell attachment, differentiation, proliferation, spreading, resorption, bone ingrowth, and contact. Microporosity depends on grain size (GS) and grain-size distribution (GSD) of granular materials used for 3D printing of scaffolds. By targeted selection and combining of granules with different GS, generating of scaffolds with defined microporosity is possible. However, changing GS and GSD will influence flowability as one of the elementary 3D printing property. The aim of this study was to examine how the change in GS and GSD affects flowability of granules and workability with 3D printing especially during recoating step. Hydroxyapatite granules with different GS and mixtures were characterized optically and tested for flowability by using different methods. The suitability for 3D printing was determined by using different recoating mechanism. For every GS and mixture, a desired recoating mechanism was identified. Finally, a correlation between GS, flowability of granules, and desired recoating mechanism could be found.