Liquid crystal display technique (LCD) for high resolution 3D printing of triply periodic minimal surface lattices bioceramics

The ability to fabricate highly porous bioceramic scaffolds with triply periodic minimal surface (TPMS) lattices that mimic the architecture of trabecular bone has been a limitation in ceramic additive manufacturing. The present paper describes a vat-photopolymerization technique using a high-resolution liquid crystal display (LCD), as a dynamic mask-generator, to manufacture TPMS constructs with porosities above 90%, pore sizes below 200 µm, and a minimum wall thickness of 38 µm. We systematically investigate the effects and mechanisms of processing variables, including refractive index and particle size distribution of powders on the cure depth of photosensitive slurries and dimensional accuracy prints made from hydroxyapatite and baghdadite (Ca6Zr2(Si2O7)2O4). Our results demonstrate that the difference between the refractive index of solid particles and the photosensitive resin is a critical factor in dictating print quality and dimensional accuracy. Additionally, we showed that irrespective of the bioceramic composition, reducing the particle size from 9.0 μm (d50) to 0.5 μm (d50), enhances the quality of the surface finish, while decreasing the smallest feature size that can be achieved. This study presents the LCD technique as a robust and effective alternative to conventional stereolithography techniques (i.e, digital light processing and scanning stereolithography) for 3D fabrication of bioceramic scaffolds and a manufacturing technique for the implementation of advanced topological optimizations of bone scaffolds and production of patient-specific implants.