Functionally Graded 3D-Printed Scaffolds through Direct Ink Writing: Bridging Ceramics and Metals for Enhanced Multifunctionality

Abstract

Over two million bone grafts are performed worldwide, each year. The preferred method is using autografts, but there are two important downsides. There is often insufficient tissue to harvest and the scar at the harvesting side is painfull for the patient. Therefore there exists a great need to improve synthetic grafts.

Traditionally, synthetic bone scaffolds are made from only one material, this can either be a (bioactive) ceramic or metal. The former has the benefit of promoting bone growth, but has insufficient mechanical properties. Metals on the other hand have no issue competing with bone in terms of mechanical properties, but they may not be biocompatible nor aid osteo-induction.

In this study direct ink writing was used to produce multimaterial Ti6Al4V and akermanite scaffolds. The goal was to combine the favourable mechanical properties of Ti6Al4V alloy with the osteo-inductive properties of akermanite. Composites of Ti6Al4V and akermanite were evaluated as well, but similar to akermanite ceramic on itself, their mechanical performance was deemed insufficient. Akermanite and Ti6Al4V was found to react and form titanium silicide and a calicum compound, presumed to be calcium oxide. A core shell scaffold was designed which uses a Ti6Al4V shell and an akermanite composite core in order to achieve both adequate mechanical and improved bioactive properties. This scaffold performed comparable to cortical bone in stiffness, and boasted superior strength.