Additive manufacturing of bone-like composites

• Main Author: Dee, Pei Fang
• Other Authors: Hortense Le Ferrand
• Format: Thesis-Master by Coursework
• Language: English
• Published: Nanyang Technological University 2023
• Subjects: Engineering::Materials::Composite materials; Engineering::Materials::Biomaterials
• Online Access: https://hdl.handle.net/10356/170508
• Institution: Nanyang Technological University

Bone is a calcium phosphate (CaP) composite possessing extrinsic toughening mechanisms due to its hierarchical structure across multiple length scales. CaP ceramics are attractive materials for bone repair due to their osteoconductivity but lack fracture toughness for loadbearing applications. Inspired by cortical bone, fabrication of CaP composites with hierarchical structures is of great research interest. In this work, microstructured CaP ceramic is made by direct ink writing (DIW), where a shear-thinning water-based ink containing CaP microplatelets is extruded line-by-line. During the material extrusion process, the CaP microplatelets are aligned depending on the shear forces experienced in the nozzle during 3D printing. After sintering CaP ceramic printed by DIW, the porous material could be impregnated with a hydrated matrix to aim for a bioceramic/hydrogel composite. Hydrogels are chosen over conventional engineering polymers, noting that bone is a living hydrated tissue. Two hydrogels were explored. Firstly, an alginate-polyacrylamide interpenetrating network was chosen for its high toughness and notch resistance. Ionic coordination between alginate and calcium is expected to strengthen the ceramic-hydrogel interface for effective load transfer. Secondly, another hydrogel chosen is polyvinylpyrrolidone-tannic acid-iron (III). Tannic acid contains catechol functional groups which act as a good crosslinker for producing adhesive materials in biomedical applications. Inspired by natural composites such as cortical bone, a combination of techniques to fabricate CaP composites with complex hierarchical structure unseen in conventional bioceramics has been explored. In future, 3D printed CaP composites with hierarchical structures could pave the way for bioactive bone repair materials.