Page 117 - IJB-8-2

RESEARCH ARTICLE

Fabrication of Microstructured Calcium Phosphate

Ceramics Scaffolds by Material Extrusion-Based 3D

Printing Approach

Peifang Dee , Sharlene Tan , Hortense Le Ferrand 1,2,3 *
1
1,2
1 School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore
2 Singapore Centre for 3D Printing, Nanyang Technological University, Singapore 639798, Singapore
3 School of Materials Science and Engineering, Nanyang Technological University of Singapore, 50 Nanyang Avenue,
Singapore 639798, Singapore

Abstract: Natural materials such as bone and enamel have intricate microstructures with inorganic minerals oriented to
perform multiple mechanical and biological functions. Current additive manufacturing methods for biominerals from the
calcium phosphate (CaP) family enable fabrication of custom-shaped bioactive scaffolds with controlled pore structures for
patient-specific bone repair. Yet, these scaffolds do not feature intricate microstructures similar to those found in natural
materials. In this work, we used direct material extrusion to 3D print water-based inks containing CaP microplatelets,
and obtained microstructured scaffolds with various designs. To be shear-thinning and printable, the ink incorporated a
concentration of 21 – 24 vol% CaP microplatelets of high aspect ratio. Good shape retention, print fidelity and overhanging
layers were achieved by simultaneous printing and drying. Combined with the 3D design, versatile CaP microstructured
objects can be built, from porous scaffolds to bulk parts. Extruded filaments featured a core-shell microstructure with
graded microplatelet orientations, which was not affected by the printing parameters and the print design. A simple model
is proposed to predict the core-shell microstructure according to the ink rheology. Given the remaining open porosity after
calcination, microstructured scaffolds could be infiltrated with an organic phase in future to yield CaP biocomposites for
hard tissue engineering.
Keywords: Robocasting; Calcium phosphate; Microstructure

*Correspondence to: Le Ferrand Hortense, School of Mechanical and Aerospace Engineering, Nanyang Technological University,
Singapore 639798, Singapore; hortense@ntu.edu.sg
Received: December 23, 2021; Accepted: February 26, 2022; Published Online: February 26, 2022

Citation: Dee P, Tan S, Le Ferrand H., 2022, Fabrication of Microstructured Calcium Phosphate Ceramics Scaffolds by Material Extrusion-
Based 3D Printing Approach. Int J Bioprint, 8(2):551. http://doi.org/10.18063/ijb.v8i2.551

1. Introduction predicts that high aspect ratio CaP platelets with
nanoscale thickness do not break, but experience pull-
Natural materials such as bone and enamel possess highly out from the protein-matrix . At present, numerous bone
[3]
complex microstructures featuring calcium phosphate
(CaP) rods or platelets oriented in multiple directions [1,2] . repair materials have been developed, including bioactive
These complex microstructural patterns are thought to glasses, hydroxyapatite composites, bone cements, and
contribute to the outstanding mechanical and functional polymers [5-7] . Among these, CaP-based scaffolds are
properties of these natural materials [3,4] . In bone, for promising due to similar chemical composition with natural
example, the local alignment of CaP anisometric bone. Furthermore, additive manufacturing, also called
nanoplatelets in an organic phase results in a combination three-dimensional (3D) printing, is now extensively used
of toughening mechanisms that increase crack resistance to fabricate 3D scaffolds enabling vascularization, cell
and prevent brittle fracture . Indeed, using the tension- invasion, and bone growth [8,9] . However, these synthetic
[4]
shear chain model, fracture mechanics theoretically bone implant materials lack the complex microstructures
© 2022 Author(s). This is an Open-Access article distributed under the terms of the Creative Commons Attribution License, permitting distribution and
reproduction in any medium, provided the original work is properly cited.
109