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

Biomaterials Advances, vol. 188, pp. 215054

Abstract

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.

Authors 6

1. Xuezhi Cao

   Loughborough University

   Affiliation as printed

   Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Epinal Way, Loughborough, LE11 3TU, UK

2. Simin Li corresponding

   Loughborough University

   Affiliation as printed

   Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Epinal Way, Loughborough, LE11 3TU, UK. Electronic address: S.Li@lboro.ac.uk

3. Manuela Pacella

   Loughborough University

   Affiliation as printed

   Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Epinal Way, Loughborough, LE11 3TU, UK

4. Lukas Masseling Aachen Fraunhofer Institute for Laser Technology ILT Aixway3D GmbH

   Fraunhofer Institute for Laser Technology

   Affiliation as printed

   Fraunhofer-Institute for Laser Technology ILT, 52074, Aachen, Germany; Aixway3D GmbH, 52074, Aachen, Germany

5. Changqing Liu

   Loughborough University

   Affiliation as printed

   Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Epinal Way, Loughborough, LE11 3TU, UK

6. Liguo Zhao corresponding

   Nanjing University of Aeronautics and Astronautics · Fuyao University of Science and Technology

   Affiliation as printed

   School of Intelligent Manufacturing and Future Technologies, Fuyao University of Science and Technology, Fuzhou, 350109, China; School of Energy and Power Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China. Electronic address: L.Zhao@nuaa.edu.cn