Laser powder bed fusion of differently designed NiTi stent structures having enhanced recoverability and superelasticity

Tubular mesh-structured NiTi stents have been integral to the biomedical industry in the treatment of arteries’ narrowings or blockages. Conventionally manufactured stents are not patient-specific and the process consists of a series of expensive and time-consuming tube drawings, laser cutting, and post-processing techniques. In this study, laser powder bed fusion (LPBF) was utilized to fabricate four differently designed NiTi stent structures with very thin struts (∼0.08–0.3 mm) which were subsequently heat treated at 550 ℃ for 6 h. Surface modification through electropolishing decreased the average surface roughness and contributed to remarkable dimensional accuracy. Structural examinations revealed only a few minor spherical gas porosities and relative densities of higher than 99.8% for all the fabricated stents. Extremely high recoverability (∼80–96%) during compression could be recorded and bending angles varied from 16.3° to 27.9° before fracture. Nanoindentation tests indicated that the parts are all having enhanced superelasticity in which recovery ratios of higher than ∼95% were achieved. Microstructural characterization identified near-identical microstructures, with equiaxed grains in axial surfaces and elongated grains in radial surfaces oriented toward< 001 > direction parallel to the building direction. Consequently, LPBF proved to be a capable alternative to fabricate NiTi stents enabling the production of patient-specific stents in near future.