Intravascular stents are mainly made of biomedical metals, alloys or medical macromolecule materials, which are manufactured by special processing, and are used as medical devices for treating stenosis or occlusion of human blood vessels. Among metal stents, airbag expansion stents made of stainless steel or cobalt-chromium alloys, and self-expanding stents made of nickel-titanium alloy Nitinol are products already on the medical market.
With the widespread use of nickel-titanium alloy self-expanding stents in the interventional treatment of diseases such as vascular stenosis, the manufacturing technology of nickel-titanium alloy stents has also been developed. It has roughly experienced three different manufacturing technologies. The original nickel-titanium alloy The self-expanding stent is a helical coil-shaped structure, and a braided mesh-structured stent appeared later. The newer technology currently is laser-cut tubular stent.
Australian research institute CSIRO Lab22 Additive Manufacturing Laboratory, in response to the needs of clinicians to improve the nickel-titanium alloy self-expanding stent, has developed a stent manufactured by selective laser melting (SLM) 3D printing technology. The stent is free in design and customizable. It shows certain advantages.
High geometric accuracy and customized
Lab22's additive laboratory has achieved many results in the field of medical device 3D printing research and development, including personalized 3D printed sternum implants and heel implants.
The Lab22 team has been exploring the feasibility of 3D printing Nitinol self-expanding stents in the laser melting additive manufacturing process in selected areas. Selective laser melting 3D printing technology can create complex vascular stents with high geometric accuracy, and at the same time it is easy to realize on-demand manufacturing of customized stents for patients.
The Lab 22 team also said that using SLM to develop Nitinol stents is challenging. The nitinol material they used was Nitinol, which is a shape memory alloy that exhibits superelasticity when pressed. The material has a unique crystal structure, which changes when subjected to pressure or heating. The two different phases of the alloy (martensite and austenite) are determined by temperature, and the phase transition temperature is extremely sensitive to the manufacturing conditions of the stent. In order for the stent to exhibit self-expansion, the transition temperature needs to be 37 ° C below body temperature. In addition, the process parameters of SLM 3D printing require ultra-fine mesh structures suitable for the manufacture of stents, including thin struts with dimensions of 80-200 μm.
According to Lab 22 Additive Manufacturing Laboratory, additive manufacturing technology provides freedom for stent design, design developers can develop the proximal and distal diameters of blood vessels of specific sizes as needed, and can also manufacture larger sizes through this process The new shape of the stent, cross branches and proximal and distal blood vessels. In addition, 3D printing technology will enhance the customized production capacity of vascular stents, reduce inventory, and increase the effective utilization of resources. For patients, this type of 3D printed special vascular stent has better vascular compliance and is expected to improve the patient experience.
Nitinol self-expanding stents have roughly undergone the evolution of three technologies: spiral coil-like structures, braided mesh-like stents, and laser-cut tubular stents.