## 2 Methods and Materials
### Design and Simulation Analysis  
The stent structure design and simulation analysis were performed using the Creo Parametric 3.0 (Parametric Technology Corp., Needham, MA, USA) and Ansys 19.2 (Ansys Corp., Canonsburg, PA, USA) software packages. Creo was used to draw the stent structure, and the two-layer structure is presented in Figure 2; the structure's main geometric parameters were defined as the strut length, strut width, crown width, and connector. The results obtained in [PERSON] et al.'s tensile tests [46] on PLA single wires were referenced for the [PERSON]'s modulus required for the stent simulation analysis; the [PERSON]'s modulus was 1400 MPa, and the Poisson ration was set to 0.35. To simplify the simulation and shorten the calculation time, a one-layer structure was used in the simulation.  
The simulation analysis was conducted using three approaches. One approach was compression analysis: first, the proposed stent had a 90-degree radial symmetrical structure and a head-tail axial symmetrical structure. Tetrahedron grids ranging from 0.13 to 0.04 mm (i.e., 0.13, 0.1, 0.07, and 0.04 mm) were used for simulation. According to the simulation results, the equivalent strain error between the 0.07 mm and 0.04 mm grids was within 1%. To reduce simulation time and meet the required simulation accuracy, a 0.04 mm grid was thus applied for subsequent simulation analysis. During the stent compression simulation, the boundary conditions were defined as the rigid tube compression fittings, frictionless support was applied to the symmetry plane, and the model was assigned to a cylindrical coordinate system. A radial displacement moving toward the axis was applied to the compression surface to compress the stent to an outer diameter of 2 mm. The second approach was the expansion analysis of the stent structure: different axial displacement was provided to the front and rear faces of the single-layer stent to simulate the different compression exerted on the stent by the elastic band, as shown in Figure 3. The simulation  
Figure 1: Conceptual map of the biodegradable, self-expanding stent: (**a**) original-size stent (diameter 4 mm); (**b**) loading the TPU elastic band onto the stent to reach the self-expanded diameter (diameter 6 mm); (**c**) stent compression; (**d**) stent compressed and inserted into a silicone tube (diameter 2 mm); (**e**) self-expanding stent inserted into an AVF.  
Figure 2: Geometry and parameter definitions of the designed stent.  
used a cylindrical coordinate system and set the direction of rotation to be fixed; thus, the stent could be deformed in the axial and radial directions simultaneously. The third approach was the radial reactive force analysis of the stent structure: the one-layer structure of the stent's axial structure was used to simulate the stent's radial reactive force. Frictionless support was applied to the axial symmetry plane, and six pairs of rigid plates were placed radially along the circumference of the stent structure. Each pair of plates was set to apply inward compression displacement in the radial direction to simulate the reactive force of the stent structure on multiplane compression.