Favorite (1)
Alleima, a company with over 20 years of experience in nitinol processing, is at the forefront of overcoming these obstacles.
In 1962, William J. Buehler discovered the shape-memory properties of nickel-titanium alloys at the Naval Ordnance Laboratory, naming the alloy family nitinol. This discovery revolutionized the medical device industry. Traditional materials like stainless steel and titanium lack the flexibility and elasticity of living tissues, leading to biomechanical incompatibility and issues such as the loosening of bone implants. Nitinol, however, closely mimics the properties of living tissue, making it ideal for implants. Its super-elasticity has paved the way for vascular implants like self-expanding stents, filters, and grafts, significantly advancing medical procedures.
The American Standard of Testing Material (ASTM) committee has developed standards for nitinol used in medical devices and implants. These standards define testing methods and specifications for nitinol in various forms, such as wire, tube, and sheet. However, without in-depth knowledge, these standards can be too broad, leading to material variation from different suppliers. Nitinol’s properties are highly sensitive, with slight changes in nickel content or cold work significantly affecting its behavior.
“I am working with a team of experienced materials specialists, development and mechatronics engineers, quality managers, and skilled operators to overcome these barriers and automate the processing as much as possible to achieve smart manufacturing for a smart material”. Dr. Bernd Vogel, a recognized nitinol expert who has been fascinated with nitinol processing since starting his university studies 30 years ago).
When nitinol is part of an assembly, carefully considering joining methods is crucial. Nitinol can be welded to itself using a laser or e-beam, but welds lack super-elastic properties and should be placed where minimal deformation occurs. Joining nitinol with other materials like titanium or stainless steel is challenging. Successful methods include soft soldering with aggressive fluxes, resistance welding, and diffusion welding. Mechanical options like crimping or shrink-fitting are generally preferred.
Alleima is one of the companies globally that can offer joining as a core capability.
The industry also faces difficulties in converting nitinol fabrication into industrial automation due to the material’s sensitivity to processing conditions. Medical products made from nitinol are often handcrafted with low automation, making the process dependent on the worker and difficult to validate. The high variety of needed versions of implants like stents makes automated processes less profitable. However, mass production of nitinol articles, such as super-elastic guide wires used in surgical procedures, has been successful due to their consistent demand and performance benefits.
Shape-restoring applications form the largest family of medical instruments made from nitinol. These products are temporarily deformed for introduction into the body and return to their original shape without temperature changes. They are used for various functions, including loops, snares, retractors, and baskets for removing foreign bodies and blood clots. In urology, stone retrieval baskets are in high demand, allowing for some degree of automation in their manufacturing process.
When manufacturing medical devices, quality is paramount, followed by productivity and profitability. Whether using manual operations or automated processes, partnering with an experienced nitinol processor is essential. Understanding the effects of cold work, heat treatment, strain rate, and cycle number on material properties is crucial for achieving the desired stress-strain behavior and ensuring the success of nitinol-based medical devices.
“In my role as Global Technology and Innovation manager at Alleima, we have built up a process that supports our customers to realize their ideas by leading them through each stage of the challenging development process of nitinol, all the way to market approval. This sets us apart from the competition”, Dr. Bernd Vogel ends.
