Microstructural and Mechanical Characterization of Thin-Walled Tube Manufactured with Selective Laser Melting for Stent Application

Abstract

This paper focuses on microstructural and mechanical characterization of metallic thin-walled tube produced with additive manufacturing (AM), as a promising alternative technique for the manufacturing of tubes as a feedstock for stents micromachining. Tubes, with a wall thickness of 500 μm, were made of 316L stainless steel using selective laser melting. Its surface roughness, constituting phases, underlying microstructures and chemical composition were analyzed. The dependence of hardness and elastic modulus on the crystallographic orientation were investigated using electron backscatter diffraction and nanoindentation. Spherical nanoindentation was performed to extract the indentation stress–strain curve from the load–displacement data. The obtained results were compared with those for a commercial 316L stainless steel stent. Both tube and commercial stent samples were fully austenitic, and the as-fabricated surface finish for the tube was much rougher than the stent. Microstructural characterization revealed that the tube had a columnar and coarse grain microstructure, compared to equiaxed grains in the commercial stent. Berkovich nanoindentation suggested an effect for the grain orientation on the hardness and Young’s modulus. The stress–strain curves and the indentation yield strength for the tube and stent were similar. The work is an important step toward AM of patient-specific stents.

Cell–Material Interactions in Direct Contact Culture of Endothelial Cells on Biodegradable Iron-Based Stents Fabricated by Laser Powder Bed Fusion and Impact of Ion Release

“…Even the corrosion process did not alter the roughness significantly, rather the forming degradation layer adapted to the 3D structure of the underlying substrate. For conventional stents in the field of cardiovascular application, a roughness Ra < 0.5 μm is envisaged . In ongoing studies, we address this issue of surface treatment to decrease macro roughness.…”

Self-Adhesion Conductive Sub-micron Fiber Cardiac Patch from Shape Memory Polymers to Promote Electrical Signal Transduction Function

“…This is similar to ref 14, owing to the addition of the electret; the viscosity of the suspension used for electrospinning decreases, and consequently, the brittleness of fibers increases with agglomeration of electret content. We adopted the maximum value of (5% PU–9% PANI–0.5% SiO 2 ) stress–strain to calculate a Young’s modulus of 0.11 MPa and based on the equation where σ and ε are the stress and the corresponding strain, respectively. We also tested the shape recovery property and tensile elasticity; the results indicated that the sub-micron fiber patch was not broken during hand stretching and could keep integrity for several seconds under 250 g counterpoise load (Figure b–e).…”

Effect of Blasting Treatments on the Surface Topography and Cell Adhesion on Biodegradable FeMn‐Based Stents Processed by Laser Powder Bed Fusion

“…The root mean squared roughness (R q ) and arithmetic average roughness (R a ) of the microblasted stent strut surfaces were reduced from 3.17 AE 0.58 and 2.66 AE 0.58 μm for glass treatment and 2.88 AE 1.08 and 2.34 AE 0.86 μm for corundum treatment compared with the as-built surface 3.94 AE 0.77 and 3.27 AE 0.62 μm, respectively. [45] Conventional laser cut stents for cardiovascular applications need an arithmetic average roughness <0.5 μm, [51] Table 2. Roughness of as-built stent struts and after microblasting with glass beads and corundum particles.…”