Extrusion of uniform-diameter polyetheretherketone–magnesium phosphate bio-composite filaments for 3D printing of design-specific multi-functional implants

Abstract

Polyetheretherketone (PEEK) is a high-performance polymer material for developing implants for orthopedic, spinal, cranial, maxillofacial, and dentistry applications. However, the major limitation of PEEK implants is their bioinertness, i.e., their incapability to integrate with tissues. Therefore, prior efforts have always focused on developing hydroxyapatite (HA) coatings on PEEK or PEEK–HA composites. However, in this study, we engineered a highly novel bioceramic known as amorphous magnesium phosphate (AMP), which surpasses the bioactivity and biodegradation kinetics of HA. Subsequently, we incorporated AMP in PEEK to develop a unique PEEK–AMP bioactive composite in the form of uniform-diameter filaments, such that it can be used in a fused filament fabrication (FFF)-3D printing setup to develop design-specific multi-functional implants. Our results indicate that controlling extrusion parameters such as temperature gradient, screw speed, tension, and cooling rate is essential in extruding uniform-diameter filaments suitable for 3D printing. Furthermore, rheological properties confirmed the suitability of the PEEK-AMP filaments for 3D printing, and SEM revealed the uniform dispersion of the AMP particles in the PEEK matrix. Importantly, PEEK–AMP composites exhibited a yield strength of 89 MPa and Young's modulus of 3.5 GPa, confirming that AMP incorporation in PEEK does not deteriorate the inherent properties of PEEK. Moreover, we prove that 3D printing can manufacture mechanically robust PEEK–AMP structures comparable to machined ones. This comprehensive study introduces a unique and first-of-its-kind bio-composite, better than existing ones, that can be used to develop standalone bioactive multi-functional implants for reconstructive and regenerative medicine and enhance patient and surgical outcomes.