Computational and experimental investigation into mechanical performances of Poly-L-Lactide Acid (PLLA) coronary stents.

Poly-L-lactide Acid (PLLA), as a credible biodegradable polymer-based material, can provide a promising amount of degradation time for vessel remodeling. Served as a sort of reliable intravascular implants, PLLA stents are expected to provide sufficient scaffolding to the target arteries without generating too much recoil after deployment. Besides, the stress and strain distribution should be as homogeneous as possible, and the stent conformability in fitting to the nature curvature of the vessels needs to be guaranteed. In the present study, mechanical performances of a stent made of PLLA material were investigated based on 3-D finite element method (FEM) and experiment verification. Simulations contained several deformation steps: crimping, spring-back after crimping, expanding and spring-back after expanding. The stent's deformation and stress/strain distributions were analyzed. Several indexes including the radial recoil ratio after crimping and expanding to different sizes, the radial properties including radial strength, the radial stiffness and the collapse pressure were established. In vitro static loading experiments of the stent were conducted as the verification of the FEM results, and a good agreement between them was obtained. Moreover, simulation of three-point bending was performed to assess the bending flexibility of the stent, and bending stiffness was defined as a measurement of structure resistance to the bending deformation.