## Materials and Methods
### Coating of the Cylindrical Stents with Paralyene C  
Zn stents of the rhombus design were coated with the polymer, Parylene C, in a conformal coating process that covered all the contours of the stent topology. It was carried out by sublimation in a  
Figure 4: Mechanical/crash test of photo-chemically etched cylindrical rhombus stents.  
Figure 3: Picture of photochemically-etched Zn ribbon.  
Physical Vapor Deposition (PVD) chamber manufactured by Specialty Coating Systems (SCS Labcoater PDS2010, Indianapolis, IN). The sublimation process resulted in the formation of an activated polymeric Parylene C inside the deposition chamber; the chemical process of sublimation is illustrated in Figure 5. The preliminary step before coating the stents with Parylene C involved treatment with a silane primer solution, which served as a coupling agent. The hydroxyl groups from the silane primer solution interact with the metal surface and enhance the attachment of the Parylene C. This combination of primer and Parylene C has been reported previously to give good adhesion of the polymer coating, along with mechanical and chemical robustness [33; 34]. The silane primer solution was prepared by mixing 1% adhesion promoter A-174 (methacryloxymethyl trimethoxysilane, Sigma-Aldrich, St. Louis, MO, USA) with 50 v % isopropyl alcohol/distilled water mixture. The primer solution was continuously stirred for 4-6 h at room temperature. Then, the Zn stents were immersed in the solution for 10 min, blow-dried and left for 20 min, followed by cleaning with 100% isopropyl alcohol in a sonication bath for a minute and subsequently blow-dried. The samples treated with the primer were transferred directly into the deposition chamber, as shown in Figure 6.  
In this work, we used a dimer Parylene C (dichloride-1_A_-xylylene--\"diX-C\", Sigma-Aldrich), which is a crystalline powdered material. The initial quantity was measured by a high-precision balance and transferred into the vaporization chamber, as displayed in Figure 6. Then, Paryelene C was heated to approximately 140-160 \({}^{\circ}\)C to initiate the sublimation process inside the vaporization chamber shown in Figure 7. The vaporized dimer of the polymer was transported to the pyrolysis chamber and heated at 670 \({}^{\circ}\)C, where it dissociated into two reactive monomer species. Finally, the monomers were directed to the evacuated deposition chamber, where the stents were located and maintained at near ambient room temperature. In this environment, the monomer vapor polymerized on the entire stent surface, coating it with a thin, uniform, and conformal layer of Parylene C. The process pressure in the PDS 2010 coater was set below 19 Pa. In order to evaluate the thickness of the polymer film, a flat silicon wafer partially masked with Kapton tape was placed next to the stents. After completing the Parylene C coating procedure, the Kapton tape was removed and a profilometer was used to measure the deposited film thickness. The thickness of the Parylene C can be varied by changing the initial amount of the crystalline powder dimer used, the process pressure and the evaporation temperature. The obtained conformal Parylene C coating was studied by Fourier Transform Infrared Spectroscopy (FTIR Nicolet 6700 instrument), Raman spectroscopy (Renishaw inVia instrument, with 514 nm Ar-ion laser and a  
Figure 5: Parylene C sublimation process.  
laser spot of \(\sim\)1 \(\upmu\)m\({}^{2}\)), Scanning Electron Microscopy (FEI SCIOS dual beam, 5 Kv, 10 KV), Atomic Force Microscopy (Veeco Dimension 3100), and Contact Angle measurements (Kruss, Drop Shape Analyzer).