In Perm, a new technology for 3D printing stents for coronary blood vessels has been developed.
The article has been published in the journal Materials. The research was conducted with financial support from the Russian Science Foundation.
Ischemic heart disease is a leading cause of cardiovascular diseases among the adult population, contributing significantly to mortality and disability worldwide. Coronary stents are used for its treatment – these are metallic frameworks that are placed within a vessel at the site of narrowing. They restore blood flow and reduce complications.
The quality requirements for such implants are high, which means that their manufacturing process must be precisely calibrated. For the past 10 years, cardiovascular stents have been produced using laser cutting technology; however, the method of selective laser melting is becoming increasingly popular, as it allows for the printing of personalized products with complex metal structures. Nevertheless, there is a lack of information regarding its application in implant manufacturing.
Scientists at Perm Polytechnic University have developed a two-stage technology for selective laser melting of cardiovascular stents made from cobalt-chromium alloy and identified the most suitable manufacturing parameters.
“Before starting the printing technology, it is necessary to design a 3D model of the future stent and assess the properties of its material – the metal powder. Cobalt-chromium alloy is often used for medical implants – it is non-toxic, does not cause allergic reactions, and is durable and long-lasting. It is crucial that it retains all these properties and does not contain harmful impurities,” explains Alexey Kuchumov, Associate Professor of the Department of Computational Mathematics, Mechanics, and Biomechanics, Head of the Biofluids Laboratory at PNIPU, Doctor of Physical and Mathematical Sciences.
“In the first stage, we conducted numerical modeling of the melting process and determined the optimal width, height, and depth of laser penetration. This is important because if the values are too small, the stent will be unacceptably thin and insufficiently strong, while too large values will lead to deviations from the 3D model. The thermal distribution of the melting process was also calculated to ensure uniformity. Numerical modeling helps avoid numerous resource-intensive experiments for determining suitable printing modes for implants,” says Andrey Drozdov, Senior Lecturer in the Department of Innovative Engineering Technologies, Researcher at the Biofluids Laboratory of PNIPU.
In the second stage, the polytechnic researchers proceeded to the actual manufacturing of the stent using selective laser melting, taking into account the values calculated in the first stage.
“Based on the experiment results, we identified the most optimal printing parameters. We considered exposure time (how long the product will be subjected to the laser radiation of the printer), the distance from one exposure point to another, and the power of the laser printer. The most suitable modes turned out to be 40 microseconds at 15 micrometers, as well as 60 microseconds at 10 micrometers – all at a power of 40 or 42.5 W. The unsuitable modes were found to be 20 microseconds at 5-15 micrometers. The stents printed with these parameters exhibited defects – too many pores, cracks, and so on,” explains Polina Kilina, Associate Professor of the Department of Innovative Engineering Technologies, Leading Researcher at the Biofluids Laboratory of PNIPU, Candidate of Technical Sciences.
The two-stage technology of selective laser melting developed by the scientists at Perm Polytechnic University could serve as an alternative to the manufacturing of microtubes and laser micro-cutting. Precise modeling and optimization of printing parameters enable the creation of more reliable personalized implants based on individual 3D models, which can improve patient outcomes and enhance the effectiveness of ischemic heart disease treatment.