Stabilization of tricalcium phosphate slurries against sedimentation for stereolithographic additive manufacturing and influence on the final mechanical properties

Abstract

Ceramic parts manufactured by lithography-based ceramic manufacturing (LCM) excel in resolution and surface quality. The material for LCM is a photosensitive ceramic particle-filled slurry which needs to have homogeneous properties over time and during each processing step. The goal of this study was to use "mechanical" stabilization for a tricalcium phosphate-filled slurry done by increasing slurry viscosity, solids loading, or inducing thixotropic behavior. The modified slurries were compared with a nonstable reference slurry. While all methods lead to increased storage stability, only the stabilized slurry with 0.5 wt% fumed silica is stable during the printing process.

Porous Calcium Phosphate Ceramic Scaffolds with Tailored Pore Orientations and Mechanical Properties Using Lithography-Based Ceramic 3D Printing Technique

“…By comparison, photo-polymerization-based AM techniques (e.g., stereolithography (SLA) [ 27 ] and digital light processing (DLP) [ 28 ]) can create more complex shapes with high accuracy and smooth surfaces since they can selectively and precisely polymerize thin layers of photo-curable ceramic slurries using high-resolution light engines [ 29 , 30 ]. Bioactive ceramics such as bioactive glasses [ 28 , 31 , 32 , 33 , 34 ], glass-ceramics [ 35 ], and CaP ceramics [ 36 , 37 ] have been investigated as the scaffold materials with the aim to construct extremal shapes and internal porous structures that are tailored for individual patients. However, to achieve sufficiently high quality, several processing parameters need to be closely controlled including the preparation of the photo-curable ceramic slurries and control over their curing behavior as well as the heat-treatment of green scaffolds for de-binding and sintering at high temperatures [ 28 , 30 , 32 ].…”

Rapid three-dimensional structuring of transparent SiO2 glass using interparticle photo-cross-linkable suspensions

“…hoto-curable suspensions have attracted extensive research attention as indispensable for designing complexstructured ceramics and glass components through additive manufacturing (e.g., digital light processing [1][2][3][4][5][6][7][8] , laser-based stereolithography 9,10 , mask projection stereolithography [11][12][13][14] , suspension-enclosing projection stereolithography 15 , and ultraviolet-assisted direct-write 16 ), in-situ solidification 17,18 , subtractive manufacturing 19 , three-dimensional micro-template replication 20 , fiber production 21 , and stop-flow lithography 22 . Thus far, various photo-curable suspensions have been designed up to date.…”

“…While the simplest process involves direct dispersion of inorganic fine particles in photo-curable monomers with photo-radical initiators [6][7][8][9][13][14][15][16][17]21,[23][24][25][26] , many researches have also focused on multi-component mixtures containing solvents to control suspension viscosities [1][2][3][4][5][10][11][12] and to form porosity in photo-cured green compacts which was favorable to debind polymers in a controlled manner 18 . Many further attempts have also made, such as by designing monomer mixtures to tune the number of reactive functional groups for controlling the photocuring rates 23 ; selecting monomers/solvents to achieve a transparent suspension and avoid light scattering 1,[17][18][19]26 , which realizes high-resolution three-dimensional printing by microstereolithography 1 ; and adding light absorbers and/or radical inhibitors to optimize the printing resolution 2,3,9,17,24 . Based on these techniques, various ceramic/glass (SiO 2 1,9,[17][18][19][20][21][22] , Al...…”

A Methylcellulose Hydrogel as Support for 3D Plotting of Complex Shaped Calcium Phosphate Scaffolds

“…Calcium phosphate scaffolds, fabricated by stereolithography, did not collapse, due to the stabilizing effect of the surrounding resin, before the resulting scaffolds were sintered. [42,43] Furthermore, calcium phosphate scaffolds were additively manufactured by indirect printing [44], lithography-based ceramic manufacturing [45] or robocasting [25]. All of these methods have in common, that combination with biologically sensitive proteins is difficult and the inclusion of cells into the fabrication process is impossible.…”