Preparation Of NHA Bone Tissue Engineering Scaffold Based On MAM Freeform Fabrication

MAM (motor assisted microsyringe) freeform fabrication is a new technology to process bone tissue engineering scaffolds, which has unique advantages in the fabracation of three-dimensional porous scaffolds with precise structure and complex micropores. Nano-hydroxyapatite (nHA) possesses satisfying chemical stability, biocompatibility and mechanical properties. And it is widely used in the regeneration and renovation of bone tissues. The preparation of nHA ceramic slurry, technology of MAM freeform fabrication and the sintering process of nHA bone tissue engineering scaffolds were investigated in the paper.The performance of the scaffold is determined by the properties of slurry. The influence of dispersant and PH on the HA slurry was firstly researched in this paper. Combined with MAM free forming tests of scaffold fabrication, it was analysed that solid fraction had effects on the scaffold processing. The 35vol% nHA ceramic slurry was prapared with 1.5% NH4PAA and PH 9～10. The moisturizer and the thickener were added to improve the jetting and forming properties of nHA slurry.The parameters of processing have direct effects on the performance of scaffolds. The optimized processing parameters were found out through lots of experiments, aiming to obtain scaffolds with perfect appearance and porous structure. The diameter of nozzle was 0.34mm, the scan speed was 5mm/s, the jetting speed was 0.004mm/s, the layer height was 0.3mm, and the center-to-center rod spacing was set to be 0.6mm or 0.8mm. Draw-back and expiation were set during the processing, to stop the leakage from the nozzle to improve scaffold quality.Sintering conditions influenced the phase composition, pore structure, microstructure and mechanical strength of scaffolds. Two different sintering methods were used in the paper, conventional sintering and microwave sintering. The influence of sintering temperature and sintering method on the phase, microstructure and the compressive strength of scaffolds was analyzed in this paper. The better sintering process was obtained. The scaffolds with linear shrinkage of 31.2% showed good pore structure with 56.2% porosity (interconnected macro pore size was 175～440μm, micro pore size was 1～10μm within the rods), and improved mechanical properties (the compressive strength was 45.2Mpa) when sintered to 1200℃for 30min by microwave sintering.