Customized PEEK implants with microporous and surface modification using 3D printing

Polyetheretherketone (PEEK) is a high-performance, semi-crystalline thermal polymer with medical advantages such as biocompatibility and radiolucency. PEEK has an elastic modulus comparable to that of human cortical bone, so it can effectively reduce the stress shielding effect caused by the mismatch between the mechanical properties of an implant and human bone tissue. However, PEEK is biologically inert, and its use typically relies on a variety of surface modification methods, such as surface coatings of bio-ceramic materials, enhancing the surface bioactivity, and osseointegration. Compared to thermal spray or plasma spray technologies, the cold spray is carried out at relatively low temperatures, retaining the original properties of the material. This research establishes an open-source three-dimensional printer compatible with PEEK and also develops a powder-spray module based on the cold spray technology that can coat the surfaces of PEEK printings with hydroxyapatite (HA) to improve its bioactivity. This paper discusses the best parameter selection for PEEK printing, a thermal history analysis of the printing process, and the adhesion of HA powder coated on PEEK specimens with different porosities. Finally, the PEEK implant is printed to measure its performance under a vertical load.