## 2 Materials and Methods  
### Stent Geometry and Materials  
Two existing stent patterns, i.e., those originally for polymeric stent [13] and magnesium stent [14] were adopted. Figure 1 shows tubular (two rings) and unfolded (planar) stent design Patterns A and B. Both stent design patterns were composed of repetitive cylindrical rings arranged in an offset manner and a plurality of axial straight links (SL) connecting the adjacent rings. Pattern A had an open-cell configuration and only the parts of adjacent ring segments were connected by axial bridge struts,whilst Pattern B had a combination of open-cell and closed-cell configurations. Each hoop ring in Pattern A was composed of circular curves (CC) with a width of 0.19 mm, presenting six peak-to-valley struts in the circular direction, and the ring was connected to the adjacent ring by three straight links with a width of 0.14 mm, evenly distributed at an angle of 120\({}^{\circ}\). Each hoop ring in Pattern B was composed of U-shaped segments (US) with a width of 0.17 mm, presenting four peak-to-valley struts in the circular direction, and the ring was connected to the adjacent ring by four straight links with a width of 0.16 mm, distributed in a specific manner.  
In the present research, a new stent design pattern was proposed by combining the characteristics of Patterns A and B, as shown in Figure 1c. To lower strain accumulation in the stent structure during stretching, the shape of the hoop ring in Pattern C was designed to be similar to Pattern B but composed of smooth circular arcs (width: 0.17 mm) in a small U-shape for improved stiffness. [PERSON] et al. [15] compared different stent geometric parameters and found that higher amplitudes in the ring segments induced high circumferential stresses over the smaller areas of the artery's inner surface than all the other configurations. Thus, in Pattern C, each ring possessed six peak-to-valley struts in the circular direction to reduce the ring amplitude. To increase the longitudinal flexibility of the MAS, an open-cell configuration was selected for Pattern C [16], with adjacent rings connected by three straight links with a width of 0.16 mm, evenly distributed at an angle of 120\({}^{\circ}\), similar to Pattern A. The whole stent models contained nineteen interlaced rings with a total length of 16.88 mm for Pattern A, eight rings with a total length of 16.09 mm for Pattern B, and seventeen rings with a total length of 18.21 mm for Pattern C.  
Two magnesium alloys, namely AZ31 and AE21, were used as the model bioresorbable materials in the stretching tests of planar stents and in the deformation tests of tubular stents with the three design patterns, respectively. Magnesium alloy AZ31 foil (Goodfellow Cambridge Ltd., Huntington, UK) with a thickness of 0.25 \(\pm\) 0.025 mm was used as the starting material in the planar stretching tests. Magnesium alloy AE21 (SHL-Alubin Ltd., Kiryat Biolik, Israel) tube with an outside diameter of 3.2 mm and a wall thickness of 0.335 mm was used as the preform of tubular stents in the deformation tests, and also in the FEA. The tube was made using a laboratory-scale extrusion press and a cold-drawing  
Figure 1: Tubular and planar stents with (**a**) Pattern A, (**b**) Pattern B, and (**c**) Pattern C. All dimensions are in mm.  
machine [17], and it had a wall thickness tolerance of \(\pm\)0.06 mm. Laser slitting was applied to produce tubular stents and planar specimens with the three different design patterns.  
Both the AZ31 alloy and AE21 alloy had a density around 1.80 g/cm\({}^{3}\), Young's modulus of 45 GPa, and a Poisson's ratio of 0.35. The yield strength of AZ31 was 188 MPa, and that of AE21 was 155 MPa. The stress-strain data obtained from uniaxial tensile tests (Figure 2) were used in the FEA.