Theoretical and Numerical Analysis of Mechanical Behaviors of a Metamaterial-Based Shape Memory Polymer Stent

Abstract

Shape memory polymers (SMPs) have gained much attention in biomedical fields due to their good biocompatibility and biodegradability. Researches have validated the feasibility of shape memory polymer stent in treatment of vascular blockage. Nevertheless, the actual application of SMP stents is still in infancy. To improve the mechanical performance of SMP stent, a new geometric model based on metamaterial is proposed in this study. To verify the feasibility and mechanical behavior of this type of stent, buckling analysis, and in vivo expansion performance of SMP stent are simulated. Numerical results exhibit that stent of a smaller radius behaves a higher critical buckling load and smaller buckling displacement. Besides, a smaller contact area with vessel and smaller implanted stress are observed compared with traditional stents. This suggests that this SMP stent attributes to a reduced vascular restenosis. To characterize the radial strength of SMP stent, an analytical solution is derived by the assumption that the deformation of stent is mainly composed of bending and stretch. The radial strength of SMP stent is assessed in form of radial force. Analytical results reveal that radial strength is depended on the radius of stent and periodic numbers of unit cell in circumferential direction.

Actuator Behaviour of Tailored Poly(thiourethane) Shape Memory Thermosets

“…Consequently, SMPs are capable of displacing loads during the recovery process, releasing their accumulated energy, and behaving like a smart actuator [ 6 , 7 , 8 ]. These outstanding properties have attracted great interest in recent decades, and their uses in a wide range of applications such as biomedicine [ 9 , 10 ], aerospace [ 11 ], textile engineering [ 12 ], and many others [ 13 ] have been studied.…”

Principles for Controlling the Shape Recovery and Degradation Behavior of Biodegradable Shape-Memory Polymers in Biomedical Applications

“…The structural integrity of biodegradable polymer stents is another actively discussed topic, considering that the primary goal of stent implantation is to achieve structural maintenance under external pressure, induced by vessel walls [ 30 , 31 , 92 , 93 , 94 , 95 ]. Laser-etched polyurethane-based stents in several geometries showed collapse pressures comparable to those of commercialized steel stents [ 92 ].…”

“…Another PU-based stent that adopted a solution-mixing fabrication method provided an increased elastic modulus, radial stiffness, and force recovery [ 30 ]. Mechanical performance and structural stability have been studied using numerical methods [ 94 , 95 ]. Stents fabricated by 3D printing are an attractive future solution for patient-personalized designs that optimize mechanical behavior in combination with finite element analysis (FEA) studies [ 31 , 93 ].…”

Smart materials in cardiovascular implants: Shape memory alloys and shape memory polymers

“…48 However, recent advances in developing different geometries of polymeric stents has allowed for the creation of stents with similar radial strength to Nitinol. 41,49 There have been recent advances in developing multistimuli responsive SMPs. [50][51][52] Most of these materials require reprograming following the initiation of the shape memory effect with the first stimuli.…”

“…Initial SMP self‐expanding stents had a radial resistive force lower than that of metallic stents 48 . However, recent advances in developing different geometries of polymeric stents has allowed for the creation of stents with similar radial strength to Nitinol 41,49 …”