The Study On Mechanical Properties Of 4D Printed Vascular Stents Based On Shape Memory Polymer

Shape memory polymers are a type of smart material that can respond to external excitations then change shape and function.The 4D printing technology based on shape memory polymer combines the advantages of smart materials and additive manufacturing,and is an effective method for rapid prototyping of complex structures.It has important applications in aerospace,electronic components,and medical.Due to its good biocompatibility and degradability,shape memory polymers play an important role in the field of biomedicine.This paper focuses on the application of shape-memory polymers in the biomedical field and study 4D printed vascular stents based on shape memory polymers.The mechanical properties of 4D printing SMP materials were characterized.Based on this,combined with the constitutive theory of shape memory polymers,the viscoelastic properties of 4D printing materials were analyzed.The 4D printed blood vessel stent structure was designed and optimized.The mechanical properties of the stent were analyzed by finite element simulation.The mechanical properties of the 4D printed stent were analyzed through experiments.The research contents of this paper are as follows:(1)The glass transition temperature and dynamic mechanical properties of shape-memory polymers were characterized by thermomechanical analysis and differential scanning calorimetry.The viscoelastic behavior of the shape memory polymer was analyzed by tensile test,stress relaxation test and creep test.(2)Design the plane and three-dimensional structure of blood vessel stents,use genetic algorithms to optimize the structure,and compare the mechanical properties before and after optimization.Stent models with different numbers of elements in the circumference were designed to analyze the influence of the elements number on their mechanical properties.(3)Static simulation of vascular stent was carried out to analyze its supporting force and suppleness;According to the environment of vertebral artery vascular,the fluid-structure coupling analysis of blood vessel stents in blood vessels was performed to study its strength and stiffness in the blood.The viscoelastic parameters of 4D printing materials were fitted by using the viscoelastic constitutive theory of shape memory polymers and experimental data,and the mechanical properties and recovery rate of the stent were analyzed.The deformation behavior of blood vessel stents in blood vessels was simulated to analyze the stent’s ability of supporting blood vessels and deformation.(4)A number of 4D printed vascular stent models were prepared and the expansion experiment was performed to analyze the effect of the number of structural units and the temperature on the shape memory performance of the stent.Through the deformation experiment of the blood vessel stent s in the counterfeit blood vessels,the function of distracting the blood vessel was verified.The vascular stents were subjected to a compression test and a three-point bend test to analyze their basic mechanical properties.