Microstructure, mechanical properties and in-vitro performance of superelastic nitinol stents produced by μ-LPBF

Additive manufacturing enables the fabrication of patient-specific self-expanding Nitinol stents. However, the relationships among processing conditions, microstructural evolution, multi-scale mechanical behaviour, and in vitro deployment performance remain poorly understood. This study carried out microstructural, mechanical and functional assessments for personalised Nitinol stents produced by micro-laser powder bed fusion (μ-LPBF). The as-printed Nitinol exhibited a predominantly equiaxed microstructure with low porosity. The austenite finish temperature remained below body temperature, indicating stable austenitic behaviour under physiological conditions. Mechanical testing further revealed a measurable superelastic response with ~3% recoverable tensile strain. Electrochemical polishing transformed a particle-covered surface into a glossy finish for the as-printed stents, with the arithmetic mean roughness (Ra) being reduced to an average value of 1.89 ± 0.60 μm. The personalised μ-LPBF stents exhibited enhanced luminal restoration during in-vitro deployment, with local expansion exceeding that of the conventional design by up to 16.84%. These results demonstrate that the personalised μ-LPBF Nitinol stents achieve improved in-vitro luminal restoration compared with the conventional geometry.