LPBF fabrication of NiTi endovascular stent-like structures and chemical etching post-processing: A feasibility study

Nitinol alloy is one of the most interesting options for the manufacture of biomedical devices, due to its superelastic behavior, which is particularly exploited for the endovascular self-expanding stents. This work intends to exploit the Laser Powder Bed Fusion (LPBF) Additive Manufacturing (AM) technique to overcome the main limitation of the NiTi: it is available only in wires or tubes and needs laser cutting to be shaped as a stent. By using LPBF, not only tubular stents can be manufactured, but other shapes can also be envisioned to treat pathologies in vessel bifurcations or in vessels with variable diameters. The work includes a dedicated experimental campaign with metallographic analyses to evaluate microstructure and defects, differential scanning calorimetry (DSC) to determine transformation temperatures, and tensile tests to assess the mechanical performance of LPBF printed coupons. Finally, a stent-like demonstrator is fabricated and chemically etched to demonstrate the proposed manufacturing route. The findings provide insight into the process parameters required to manufacture stent-like NiTi structures by 3D printing, establishing a process chain and dimensional control approach capable of producing geometries within the range reported for commercial .peripheral self-expanding stents. In this respect, the present process validation constitutes a necessary foundation for the subsequent optimization of thermal post-processing aimed at restoring appropriate transformation temperatures and functional behavior. The work therefore supports the future development of patient-specific NiTi stents, provided that the required heat-treatment route is successfully established.