3D-printed braided nitinol stents survive 50% compression in lab

A stent that can be squeezed to half its width and spring back without cracking is what a catheter needs to carry it into a narrow vessel. In a lab in Madrid, the team at IMDEA Materials Institute and Universidad Politécnica de Madrid (UPM) has printed such stents as braids, in one single production step. The work was led with researchers from the Massachusetts Institute of Technology (MIT) and the University of Galway, and the method is patented.

The problem they address is geometric. Most metal medical devices made by additive manufacturing, the industrial name for 3D printing, use lattices: repeating networks of rigid struts. Compressed, these lattices become excessively stiff, press hard on artery walls, and can fracture at strains approaching 25%. The braided design instead lets its interwoven filaments slide and reorient, as a textile mesh does. As Carlos Aguilar Vega, one of the study's authors, put it, lattices made with conventional additive techniques cannot reach the reversible deformation that catheter procedures require, while braids "can readily accommodate the large deformations required while maintaining both structural integrity and elastic recovery."

A printed part is not yet ready for a body. A chemical etching and electropolishing treatment smooths it to a biomedical-grade finish, and it also thins the fibers: fiber thickness fell by 47.7% and cross-sectional area by 71.1% compared with the as-printed structures. After that step, the braided stents withstood compression of up to 50% of their original diameter while keeping more than 90% elastic recovery. Their chronic outward force, the steady push they exert on the vessel wall, was up to five times lower than in conventional lattices, which the researchers link to a lower risk of vascular injury and thrombosis, meaning clot formation.

For a patient, the practical promise is custom-fitted devices. The researchers also show prototypes shaped for a fenestrated bifurcation stent and a customized aortic valve frame reconstructed from patient CT scans, and they point to smaller neurovascular devices for hard-to-reach regions of the brain as the next frontier, which would need more miniaturization and magnetic navigation. But the sources are clear about the distance left: the prototypes passed only mechanical tests, and in vitro biocompatibility tests and animal studies must come before any clinical investigation in patients. No date for that step is given, and IMDEA says it will pursue these research directions in the coming months. So the change, for now, is for device designers and surgeons who want implants fitted to an individual anatomy. Patients will feel it only once those next tests are passed.