Improvement of Mechanical Performance of Bioresorbable Magnesium Alloy Coronary Artery Stents through Stent Pattern Redesign
2. Materials and Methods
2.1. Stent Geometry and Materials
2.2. Analysis of Stretching Behavior of the Planar Specimens
2.3. Experimental Evaluation of Stretching Behavior of the Planar Specimens
2.4. FEA of Deformation Behaviors of the Tubular Stents
- Step 1.
- Crimp the stent specimen to an outside diameter of 2.5 mm;
- Step 2.
- Release the crimper and let the stent specimen recoil;
- Step 3.
- Expand the stent specimen to a specific inside diameter (2.67 mm for Stent B and 2.52 mm for Stent C);
- Step 4.
- Release the expander and let the stent specimen recoil.
- Step 1.
- Move the upper load applicator downwards and bend the stent specimen to a deflection of 1.4 mm;
- Step 2.
- Retract the upper load applicator and release the stent specimen to let the spring-back of the bent stent occur.
2.5. Experimental Evaluation of Deformation Behaviors of the Tubular Stents
3.1. Stretching Behavior of the Planar Specimens
3.2. Crimping Behavior of the Tubular Stents
3.3. Expanding Behavior of the Tubular Stents
3.4. Radial Strength of the Tubular Stents
3.5. Flexibility of the Tubular Stents
- In terms of scaffolding capacity and radial recoil, the performance of Pattern C was better than that of Pattern B.
- A new stent design pattern proposed for magnesium alloys (Stent C) exhibited balanced radial strength and deformability. In comparison with the existing stent pattern designs (Stents A and B), Stent C had a compromised overall mechanical performance in expanding deformability, radial strength, and radial recoil. However, the expanding capacity of Stent C would need to be improved.
- The crimping deformability of Pattern C was comparable with that of Pattern B, and better than that of Pattern A. Stent A exhibited non-uniform shrinkage and rotated axial links during crimping, and then cracking and fracture occurred. Thus, this design pattern would not be suitable for magnesium alloy stents.
- Stent C had bending flexibility comparable with Stent B at low deflections and it had far better bending flexibility than Stent A. The advantage of Stent C over Stent B became apparent when the bending deflection exceeded 0.6 mm. Stent B had poor consistencies at large deflections due to the squashing of the stent circular rings, where Stent A and C performed much better.
- Stent pattern redesign could open up new possibilities for magnesium alloy stents to meet the performance requirements of bioresorbable coronary artery stents, despite the low ductility of magnesium alloys at normal body temperature.
Conflicts of Interest
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|Stent A||Stent B||Stent C||PLLA Stent |
|Bending stiffness (Nmm2)||60.1||42.1||41.5||2.9|
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Wang, Q.; Fang, G.; Zhao, Y.-H.; Zhou, J. Improvement of Mechanical Performance of Bioresorbable Magnesium Alloy Coronary Artery Stents through Stent Pattern Redesign. Appl. Sci. 2018, 8, 2461. https://doi.org/10.3390/app8122461
Wang Q, Fang G, Zhao Y-H, Zhou J. Improvement of Mechanical Performance of Bioresorbable Magnesium Alloy Coronary Artery Stents through Stent Pattern Redesign. Applied Sciences. 2018; 8(12):2461. https://doi.org/10.3390/app8122461Chicago/Turabian Style
Wang, Qian, Gang Fang, Ying-Hong Zhao, and Jie Zhou. 2018. "Improvement of Mechanical Performance of Bioresorbable Magnesium Alloy Coronary Artery Stents through Stent Pattern Redesign" Applied Sciences 8, no. 12: 2461. https://doi.org/10.3390/app8122461