3D printing of multi-scale porous β-tricalcium phosphate scaffolds: Mechanical properties and degradation

Abstract

Processing-structure-property relationships of 3D-printed multi-scale porous ceramics were investigated. Direct ink writing (DIW) of oil-templated colloidal pastes produced hierarchically porous beta-tricalcium phosphate (TCP) scaffolds. Print architecture and microporosity within filaments were varied, mimicking bone structure. The scaffolds exhibited 60–70 % porosity with interconnected macropores 300–700 μm and microporosity within the filaments at the 10 micron-scale. Varying surfactant and oil concentrations created two micro-pore morphologies – bubble-like pores (emulsion) and channel-like pores (capillary suspension). Emulsion scaffolds were stronger, stiffer and more reliable than capillary suspension scaffolds under both compression and bending. Reducing nozzle diameter and inter-filament distance improved strength and stiffness, at lower density. Immersed at physiological pH, the hierarchically porous TCP scaffolds' strength and modulus degraded at a moderate rate suitable for bone tissue engineering (BTE). Mechanical behavior can be controlled by manipulating process parameters which influence the material's structure. These properties were comparable with trabecular bone, promising for BTE.

Keywords

• Direct ink writing
• Hierarchical porosity
• Bone scaffolds
• Strength
• Elastic modulus
• Calcium phosphates