Study On Surface Microstructure Design And Fabrication Of Titanium Alloy Bone Prosthesis Based On 3D Printing And Its Properties

Every year,there are tens of millions of cases of severe bone tissue diseases caused by population aging,car accidents and tumors.Orthopedic clinic is in urgent need of research and development of bone tissue prosthesis with personalized size characteristics and excellent bone integration effect.The surface of bone tissue repair is an important interface for the interaction between the host bone tissue and the implant material,and it is the main site for the adhesion,proliferation and differentiation of osteoblasts.It plays a decisive role in osteointegration and bone tissue repair and reconstruction.In this paper,the selected laser melting 3D printing technology was used to prepare orthopedic implants with personalized macro size characteristics.By adjusting the key process parameters in 3D printing,a new method based on reducing energy density was proposed to construct bone tissue engineering scaffolds with micron-scale pore surface structure characteristics.Then,the micronscale pore structure on the surface of the scaffold was further optimized by pickling alkali heat treatment to form a micro-nano topological bionic structure.Finally,the multi-level,multi-scale,three-dimensional micro-nano topological structure design of the bionic bone tissue was completed to improve the osteogenic activity of the bone tissue engineering scaffold.This paper has carried out research work in the following aspects:(1)In this paper,the influence of laser power,scanning speed and scanning distance on the surface morphology of single and multilayer melt by selective laser melting was discussed.It was found that with the decrease of laser power or the increase of scanning speed,the width of single melting pool decreased gradually.When the linear energy density was less than 100J/m,the microstructure characteristics of random pore surface began to appear.When the linear energy density was between 34 J/m and 78J/m,the random pore structure was most obvious.With the increase of scanning distance,the melting pool was gradually pulled apart.When the scanning distance was greater than 0.12 mm,the surface microstructure characteristics of regular holes began to appear.The adjustment of laser power and scanning speed mainly had a great influence on the dimensional accuracy of the scaffold in the Z direction,and a little influence on the X/Y direction,while the adjustment of scanning distance had a great influence on the dimensional accuracy in the X/Y direction.The method of preparing random pore structures by adjusting the laser power had obvious effect on the massive and porous scaffolds,while the method of preparing regular pore structures by adjusting the scanning distance had better effect on the massive scaffolds.The control principle and rule of customizing the surface microstructure of bone scaffold by adjusting the printing process parameters were put forward.(2)The physical properties and biological functions of the random pore structure surface were tested and analyzed.It was found that with the decrease of laser power,the random pore structure gradually became obvious,the porosity of the scaffold increased from 4.6% to 41.5%,and the surface roughness increased from 11.46?m to21.97?m.When the laser power was less than 60 W,the surface of the random pore showed excellent hydrophilicity and the contact Angle was 0°.The compressive strength of the porous scaffold decreased from 238.31 MPa to 11.51 MPa,and the elastic modulus decreased from 3.59 GPa to 0.11 GPa,showing certain plastic fracture characteristics.It was found that the growth rate and state of the cells on the surface of the massive scaffold with random pore structure were worse than that on the surface without microstructure,but the overall biocompatibility was good.However,experiments on porous scaffold cells showed that the bioactivity of random pore surface was better than that of non-porous surface.The surface of random pore structure was conducive to the infiltration and growth of cells into the inside of the scaffold and further improved the bone integration performance.(3)The physical properties and biological functions of the surface of the regular pore structure were tested and analyzed.It was found that the regular pore structure gradually appeared with the increase of scanning distance.The porosity of the scaffold increased from 7.3% to 38.3%,and the surface roughness increased from 14.41?m to38.41?m.When the scanning distance was greater than 0.16 mm,the surface of the regular hole formed had excellent hydrophilicity,and the contact Angle was 0°.With the increase of scanning distance,the mechanical properties of porous scaffolds changed little.Compared with the surface without microstructure,the initial growth rate of cells on the regular pore structure surface was faster and the cell spread was better.In the later stage,the pore structure surface close to the cell size was more conducive to the proliferation and differentiation of cells,and showed better osteointegration performance.