| Faced with the phenomenon that more and more people have suffered from vascular obstructive diseases which seriously threaten the health and security of human life,it is very important to develop customized and personalized vascular stents with good mechanical properties,biocompatibility and biodegradability.Polylactic acid(PLA)has good biocompatibility,biodegradability and processability,and also has shape memory effect,which is an ideal material for vascular stenting.Fused deposition modeling(FDM),one of 3D printing technologies,has simple and reliable equipment.The processing technology of FDM is not limited by geometry complexity,which is suitable for personalized and customized processing of complex structure vascular stents.Based on the study of mechanical properties and shape memory effect of FDM printed PLA samples,we have printed PLA vascular stents with negative Poisson's ratio structure.The 3D printing of PLA vascular stent enriches the methods of manufacturing for vascular stent.The influence of the size parameters of the 3D printed PLA vascular stent on the radial strength and longitudinal flexibility of the stent has been studied to provide the basis for the design and manufacture of the stent.The negative Poisson's ratio effect,the diameter recovery ratio and length recovery ratio of 3D printed PLA vascular stent have been studied,which provides a new idea for stent implantation and expansion.In order to study the mechanical properties of 3D printed PLA samples and identify the FDM 3D printing parameters suit for PLA negative Poisson's ratio stent,single factor experiment is used to study the influence of layer thickness,raster angle and number of contours on tensile,flexural and compressive strength of 3D printed PLA samples.The results show that the layer thickness has a significant effect on the mechanical properties of 3D printed PLA samples.With the increase of layer thickness,the tensile,flexural and compressive strength of 3D printed PLA samples decrease gradually.While the influence of raster angle and number of contours on mechanical properties is relatively small.The shape memory effect of 3D printed PLA samples is researched.The influence of FDM parameters—namely,layer thickness and raster angle—and deformation temperature and recovery temperature in shape memory creation procedure on the shape recovery ratio and the maximum shape recovery rate is evaluated using the orthogonal experimental design method.Range analysis and ANOVA analysis indicate that the sequence of the magnitude of effect of the four factors on the shape recovery ratio is as follows:recovery temperature,deformation temperature,raster angle and layer thickness.The factors affecting the maximum shape recovery rate,in descending order,are recovery temperature,layer thickness,deformation temperature and raster angle.Under different parameters,the highest shape recovery ratio is 98%,and the maximum shape recovery rate is 2.036 mm/s,which indicates that a large shape memory effect of the PLA shows potential for application in self-expanding vascular stents.Based on the study of mechanical properties and shape memory effect of 3D printed PLA samples,the PLA vascular stents with different diameter,different wall thickness and different unit geometric parameters of arrow shaped negative Poisson's ratio structure are manufactured.The mechanical properties of PLA vascular stents are tested.The influence of diameter,wall thickness and unit geometric parameters on the radial strength and longitudinal flexibility of FDM printed PLA vascular stents has been obtained.The results show that the increase of stent diameter not only makes the radial strength of 3D printed PLA vascular stents become lower,but also reduces the longitudinal flexibility.The increase of the wall thickness of the stent strengthens the radial strength of 3D printed PLA vascular stents but the longitudinal flexibility is reduced.The change of unit geometric parameters leads to the change of the surface covering ratio.And the increase of surface covering ratio leads to the increase of radial strength but the decrease of longitudinal flexibility.In the experimental research on shape memory effect of 3D printed PLA vascular stents,when the 3D printed PLA vascular stent with arrow shaped negative Poisson's ratio structure is crimped by crimping device under deformation temperature,the radial and longitudinal size of stent can decrease at the same time.And the stent with negative Poisson's ratio structure can expand simultaneously in both radial and longitudinal direction.When the deformation temperature and recovery temperature are both 65~oC,the diameter recovery ratio of stent is more than 95%and the maximum can reach 98%.The length recovery ratio is above 97%.This indicates the feasibility of utilizing the shape memory effect of PLA to realize the gradual expansion of 3D printed PLA vascular stents under temperature excitation. |
PDF Full Text Request