Hybrid direct ink writing of silicone-based emulsions for advanced hardystonite bioceramic scaffolds

Hardystonite (Ca 2 ZnSi 2 O 7 ) is an advanced Ca-Zn silicate bioceramic that demonstrates an excellent balance between biological response and mechanical performance. While it shows great promise for tissue engineering applications, achieving complex architectures presents significant challenges. This study emphasizes the synergy between polymer-derived ceramics and additive manufacturing (AM) as an effective and versatile approach for creating hardystonite-based porous structures. This is made possible through emulsification of aqueous nanodroplets within a silicone paste, supported by surfactants; the nanodroplets may contain CaO- and B 2 O 3 -yielding compounds in solution and ZnO nanoparticles in suspension. The emulsified pastes exhibit a suitable pseudoplastic behavior for the shaping of reticulated porous scaffolds by direct ink writing (DIW); the stability of geometries, before ceramic conversion of the printed bodies, is enhanced by UV curing, supported by photocurable acrylates within the silicone matrix. Phase pure Ca 2 ZnSi 2 O 7 ceramics were achieved by heat treatment at 1200 °C in air. The incorporation of B 2 O 3 enhanced the ionic interdiffusion and promoted the formation of B-containing hardystonite solid solution, at much lower processing temperature (1000 °C); it also significantly affected the porosity distribution and the resulting mechanical performance.