• Researchers at IMDEA Materials Institute and Universidad Politécnica de Madrid (UPM) have created implants capable of adapting to each patient’s anatomy.
• The combination of 3D printing and metamaterials enables structures that are more flexible than conventionally manufactured devices.

An international research team led by IMDEA Materials Institute and Universidad Politécnica de Madrid (UPM) has developed a pioneering method for manufacturing personalised cardiovascular medical devices using three-dimensional printing of nitinol, a superelastic alloy.

This breakthrough, published in npj Metamaterials (Nature Portfolio), also involved researchers from the Massachusetts Institute of Technology (MIT) and the University of Galway, and enables the design and manufacture of highly flexible braided structures in a single production step.

The technology has already been patented, and its innovative potential has been recognised with the National James Dyson Award, one of the world’s most prestigious international awards for young engineers and designers.

These structures mimic blood vessels and can be compressed without failure, enabling their delivery through a catheter.

The research addresses one of the principal challenges in the design and manufacture of minimally invasive transcatheter devices (MITDs): the difficulty of developing implants with complex three-dimensional geometries, tailored to the specific needs of individual patients and capable of being compressed for implantation through a catheter.

“The clinical impact of nitinol-based MITDs has been transformative for cardiovascular interventions,” explained Dr Carlos Aguilar Vega, one of the authors of the publication.

“However, despite their widespread clinical adoption, current manufacturing methods impose fundamental geometric limitations that restrict their optimisation and personalisation.

“While recent advances in powder metallurgy-based techniques, such as spark plasma sintering, have expanded the manufacturing possibilities for these devices, it remains challenging to develop implants that combine complex geometries, mechanical flexibility and patient-specific anatomical adaptation,” he added.

Most metallic medical devices produced through additive manufacturing are based on lattice structures, consisting of networks of interconnected elements arranged in repeating patterns. While these architectures are relatively straightforward to design and manufacture, their mechanical behaviour relies primarily on the bending of rigid struts.

This represents a major limitation for transcatheter applications, where implants must be compressed to fit inside small-diameter catheters, navigate through blood vessels, and subsequently recover their original shape after deployment, all without suffering permanent deformation or fracture.

The researchers found that conventional lattice structures are unable to withstand the large deformations required by these procedures. As they are compressed, they become excessively stiff, exert high forces on arterial walls and face a significant risk of fracture at strains approaching 25%.

Braided architectures, by contrast, behave very differently. Rather than deforming through the bending of rigid elements, they accommodate deformation through the movement and reorientation of interwoven filaments, in a manner similar to conventional braided stents or textile meshes.

To achieve the biomedical-grade surface finish required for implantation, the team applied a combined chemical etching and electropolishing treatment.

Testing showed that this post-processing step reduced fibre thickness by 47.7% and cross-sectional area by 71.1% compared with the as-printed structures. As a result, the new braided stents were able to withstand compressions of up to 50% of their original diameter while maintaining more than 90% elastic recovery.

In addition, the chronic outward force (COF) was up to five times lower than that observed in conventional lattice structures, significantly reducing the risk of vascular injury and thrombosis.

“Lattice structures manufactured using conventional additive manufacturing techniques are unable to achieve the high degree of reversible deformation required for transcatheter applications,” said Dr Carlos Aguilar Vega.

“Braided architectures, on the other hand, can readily accommodate the large deformations required while maintaining both structural integrity and elastic recovery.”

The research team successfully validated several prototypes from a mechanical standpoint using widely accepted performance indicators and a single compression-expansion cycle that replicates the actual insertion of the device into a catheter and its subsequent deployment.

Although these results are promising, the next steps include in vitro biocompatibility testing and animal studies before clinical investigations in patients can begin.

The researchers also identify the development of neurovascular devices capable of addressing diseases in remote and difficult-to-access regions of the brain as one of the next frontiers in the field.

Achieving this goal will require further miniaturisation of complex NiTi structures, exploring technologies such as ultra-high-precision three-dimensional printing based on two-photon polymerisation using metallic suspensions, as well as magnetic functionalisation to enable remote magnetic navigation.

These are among the research directions that IMDEA Materials Institute intends to pursue in the coming months.