Additive Manufacturing Of Hydroxyapatite Bone Scaffolds Via Digital Light Processing

Hydroxyapatite(HA or HAP)is a kind of biocompatible bioceramics and also an ideal artificial bone material.In order to promote the adhesion,proliferation and differentiation of human osteoblasts,artificial bone materials usually need to be processed into porous bone scaffolds.However,the traditional forming method of porous ceramics has many limitations.It can not form some complex bone scaffolds,nor can it accurately control the pore size,shape and distribution of the pore structure.In recent years,3D printing technology has developed rapidly,and has a great application prospect and development space in the field of porous bone scaffold manufacturing.The forming process of hydroxyapatite porous bone scaffold was studied for the first time by the technology of digital light possessing method.The main research contents are as follows:(1)A resin-based hydroxyapatite paste suitable for DLP 3D printing was prepared.By using Guang Min resin,dispersant and ceramic particles,the slurry with solid content of 20-60 wt%was prepared.The rheological properties of each slurry at 20-60?were compared,and the formability of the slurry was verified by reverse die forming and projector forming.(2)In this paper,a high precision DLP ceramic photocuring printer was used to determine and optimize the forming parameters of a set of resin based hydroxyapatite slurry.According to the requirements of printer forming,the slurry with solid content of 45 wt%was selected.The influence of light intensity and illumination time on the thickness of solidified layer had been studied.The relationship between the thickness of solidified layer and the exposure energy was obtained by fitting.Combining the forming efficiency,the parameter range of the single solidified layer was determined.Finally,the forming parameters of the green body were determined:the thickness of the single layer100?m,light intensity 10000?W/cm ~2,curing time 4 s,forming temperature 50?.(3)The degreasing and sintering curve was determined by means of thermogravimetric and differential scanning calorimetry(TG-DSC)combined with the characterization parameters of the quality of the formed samples.Finally the hydroxyapatite samples with less defects and higher precision were sintered.The linear shrinkage of different samples is 31.9-39.5%,the volume shrinkage is 72-74%,the density is about 94.9%,the microhardness is between 164.2-280.6HV and the grain size distribution is between 2-10?m.Further analysis shows that some hydroxyapatite is decomposed into calcium phosphate after sintering and the decomposition rate is about 2.3%.(4)A porous scaffold structure suitable for bone repair was designed and formed.The porosity of the scaffold is 49.8%.The biocompatibility of MC3T3 cells in vitro showed that hydroxyapatite porous bone scaffolds had no toxicity and could promote the adhesion,proliferation and differentiation of osteoblasts.