Preparation And Performance Of Porous TPMS Scaffold Based On Selective Laser Sintering

Additive manufacturing(AM)has opened up new horizons in bone tissue engineering with its advantages in the manufacture of complex parts.Among them,selective laser sintering(SLS)can accurately control the pore structure of bone scaffolds and sinter a variety of composite materials,so it is favored by people.Bone scaffolds need to meet good mechanical and biological properties.Polylaurolactam(PA12)is a commonly used sintered material for SLS,and its molded parts have good mechanical properties;hydroxyapatite(HA)can effectively promote bone growth.Therefore,this article takes SLS forming PA12/HA composite TPMS porous scaffold as the goal.First,determine the optimal process parameters of SLS,then design the pore structure for the scaffold,and then use SLS to prepare bone scaffolds with different composite materials.Through compression experiments and biological activity tests,the mechanical properties and biological properties were studied.Finally,a gradient porous bone scaffold was designed and formed,and the mechanical properties were used as indicators for discussion.In order to study the optimal process parameters of SLS,six different process schemes were designed in this paper,and PA12 sintered parts were prepared for regular exploration.Through comprehensive analysis of the density,dimensional accuracy,cross-sectional morphology,compression performance and finite element molten pool of the sintered parts,it is determined that the sintered parts with an energy density of0.08J/mm~2 have the best performance.At the same time,combining the equipment parameters obtained from multiple experiments,the optimal process parameters are obtained as follows:preheat temperature 170℃,powder layer thickness 0.1mm,substrate thickness 10mm,scanning distance 0.12mm,laser energy density(AED)0.08J/mm~2(P=12W,V=1500mm/s).Aiming at the design of the pore structure of the bone scaffold,this paper uses the Schwarz P,Diamond,and Gyroid three-period minimal surface(TPMS)structure as the basis,and uses the Grasshopper software to realize the parametric modeling of the scaffold curvature(a)-porosity(K).The SLS stent was formed with PA12 material,and the mechanical properties of the P-curved stent were found to be the best through compression tests.Subsequent experiments were carried out with P-curved stent structure for research.For the PA12/HA composite bone scaffold,this article discusses the physical and chemical properties of the composite material,biological properties,and the influence of different porosities on the mechanical properties of the composite bone scaffold.Firstly,it was determined from the perspective of phase and thermal analysis that the composite materials with different proportions did not undergo physical or chemical reactions.Subsequently,4 different PA12/HA ratio schemes were designed,each of which formed 6 types of stents with porosity of 50%,55%,60%,65%,70%,and 75%respectively.Through the compression test of each group of scaffolds,the relationship between scaffold porosity(K)and corresponding elastic modulus(E)is obtained,So as to realize the parameterized modeling of the curvature of the scaffold(a)-porosity(K)-elastic modulus(E)in Grasshopper.In order to determine the best proportioning scheme,this article carried out hydrophilicity test,cross-sectional morphology observation,CCK-8 inspection on the stents formed with different proportions,combined with composite finite element sintering analysis,and finally determined 96%PA12/4%HA is the best ratio of bone scaffold composite materials.Relying on the a-K-E parametric modeling method of the scaffold,three gradient porous scaffolds were constructed with porosities of 55%-59%-64%(A),64%-55%-59%(B),and 55%-64%-59%(C).Axial and radial compression experiments were carried out on the composite gradient bone scaffold formed with 96%PA12/4%HA.The results showed that the compression modulus of radial compression was much higher than that of axial compression;The compressive modulus and yield strength of group B are the highest under radial compression,which are 348.07MPa and 12.26MPa respectively;In axial compression,the compressive modulus and yield strength of group A are the highest,248.45MPa and 12.06MPa,respectively.