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High-Performance Self-Expanding NiTi Stents Manufactured by Laser Powder Bed Fusion
Xiang Li,Shijie Hao,Baopeng Du,Bo Feng,Haohang Li,Ping Qiu,Bingmin Huang,Lishan Cui,Ying Yang 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.5
Laser powder bed fusion (LPBF) is a promising technology for the manufacturing of customized medical implants, due tothe intrinsic potential in the fabrication of components with complex geometries. However, for the LPBF-produced vascularimplants, the dimensional accuracy, forming quality and surface finish are still unable to satisfy the medical requirements. This work provides a systematic study on dimensional accuracy control, relative density, surface polishing, shape memoryfunction, superelasticity property and deployment capability of LPBF-produced self-expanding NiTi stents, aiming at promotingtheir application in the biomedical field. The dimensional deviation of stent struts between designed prototype andas-melted products is reduced to 3% by applying laser beam compensation (LBC) strategy. Meanwhile, the study reveals thatthe LBC parameters have strong influence on the relative density of NiTi stents. 99.89% of relative density is achieved forLPBF-produced NiTi stent as the LBC value is optimized to 120 μm. The incompletely melted powders, balling and rippingstructures on the surface of NiTi stents are observed to exhibit different removal processes during electrochemical polishing. The surface roughness (Ra) of NiTi stent is decreased from 7.17 μm for as-melted stent to 0.34 μm for as-polished one. Basedon high relative density and surface quality, the stents exhibit excellent shape memory function and superelasticity propertyin the process of cyclic deformation. Finally, the deployment capability of the stents is assessed. The results confirm thatLPBF-produced NiTi stents can be successfully crimped and released during the deployment process.