Abstract

Extrusion Freeforming of Ultrafine Bioceramic and PEEK Tissue Engineering Scaffold

Shoufeng Yang, Professor, Chair of Additive Manufacturing, University of Southampton

Extrusion-based additive manufacturing (AM) technologies offer the ability to rapidly print functional complex 3D structures from variety of inks/pastes with different resolutions. Minimum feature size printed from ceramic colloidal inks is limited to circa 70µm as these inks either experience nozzle jamming (or clogging) or need exceedingly high pressure to impel ceramic ink to flow through a fine nozzle. In this talk, the parameters affecting the extrusion resolution, including ceramic paste formulation, extrudate velocity, and nozzle geometry, will be discussed. An extrusion-based AM system was designed and set up and series of experiments were conducted to analyse the effects of paste solvent content, extrudate velocity and die design on extrusion pressure using the Benbow’s model. In addition, factorial design of experiment (DOE) was served for statistical analysis of contribution of each control factor on the extrusion pressure and the results were considered as a guide for 3D direct writing of high resolution hydroxyapatite (HA) scaffolds. HA scaffolds with filaments as fine as 30µm could be printed for the first time by carefully adjusting the process parameters. This bioceramic scaffold have also been used to produce bioactive PEEK/hydroxyapatite (PEEK/HA) composite with a unique configuration in which the bioactive phase (i.e. HA) distribution is computer-controlled within a PEEK matrix. 100% interconnectivity of the HA network in the biocomposite represents superior advantage over alternative forms of production. Moreover, the technique can be employed to produce porous PEEK structure with controlled pore size and distribution, facilitating greater cellular infiltration and biological integration of PEEK composites within patient tissue. The results of unconfined, uniaxial compressive tests on these new PEEK/HA biocomposites with 40% HA under both static and cyclic mode were quite promising, showing the composites possess yield and compressive strength w