By Sean Fenske, Editor-in-Chief

Medical devices are one of the most critical products that can be manufactured. However, not all companies dedicate resources to the industry when they also serve multiple other markets. In fact, since the medtech industry is often working in small volumes compared to consumer, industrial, or automotive, it can be challenging to gain the necessary access to certain material supply chains.

Fortunately, there are companies that have dedicated their attention to the medical device manufacturing industry’s needs. One example of this is firms providing the unique metal Nitinol. The material is used by several industries, but since it is not easily processed, there aren’t a large number of providers of it. Medtech manufacturers who require the metal are better served working with a dedicated supplier and processor of it.

To help further explain this novel material and the challenges involved with its availability, Jonathan Howe, Senior Director of Corporate Development at Confluent Medical Technologies, took time to speak with MPO about it. In the following Q&A, Howe provides insights on the metal, what makes it difficult to process, and what the status of its availability is.

Sean Fenske: What makes Nitinol an attractive material for medical device manufacturing?

Jonathan Howe: Nitinol’s super elastic and shape memory properties make it ideal for a number of medical device applications, particularly for interventional therapies like structural heart valves and neurovascular stents. These therapies require devices that can be delivered minimally invasively within some fairly tortuous arteries or veins and then provide structural support to restore anatomical function. Some of these applications require the structural support to have a very high fatigue life (think how many times your heart beats in a year or, for some of these applications, decades).

Fenske: In what types of form factors is the material offered and for what applications are these commonly used?

Howe: The Nitinol raw materials (or mill product) come in coil and rod formats, which are typically converted into a wire or tube. These Nitinol wires and tubes are then converted into components. For example, tubes are often further processed using lasers and secondary processes to cut and shape the material to the design specifications.

Nitinol is used in a wide area of medical device markets such as structural heart, cardiovascular, neurovascular, peripheral vascular, ENT, pulmonary, and orthopedic markets. Essentially, for medical device markets that require minimally invasive surgery and some level of structure support/strength, Nitinol is the ideal material choice.

Fenske: Why is the supply of this material limited to certain manufacturers? What are the challenges involved in the manipulation of it?

Howe: In order to understand why there are limited manufacturers, it is first important to understand some of the important material requirements of Nitinol. Two of these requirements are the transition temperature and the non-metallic inclusions.

The transition temperature is the temperature at which the Nitinol material changes from one phase (austenitic) to another phase (martensitic). This phase change triggers the material’s shape memory properties. The temperature window in which the material has to transition is pretty tight (think room temperature vs. body temperature differences). This means the material needs to have a precise and repeatable transition temperature.

Also, as previously mentioned, a number of Nitinol device applications require high fatigue resistance. It has been shown that the size and amount of non-metallic inclusion in the Nitinol material can affect the device’s fatigue resistance.

Finally, most medical devices require the Nitinol material to conform to ASTM F2063, which defines these transition temperatures and non-metallic inclusion levels.

Given these two critical Nitinol design requirements, we can now turn to why the material’s supply is so limited.

Nitinol is created by combining roughly equal parts of nickel and titanium. The trick is in a relatively small change in the mixture—in the range of approximately 0.1% or less—which can have a large impact on the transition temperature. This ratio needs to be consistent throughout the entire Nitinol device. These medical devices are often less than a gram in size, yet the Nitinol manufacturing process to melt and mix them is in batch sizes of hundreds to thousands of kilograms. For any Six Sigma readers, this translates to needing Six Sigma capability on the uniformity of the materials to control composition variations of less than 0.1%. Note the batch sizes need to be this large in order to achieve the scale required to minimize cost and maintain lead times.

During the melting process to create the homogenous mixture, there are some byproducts that need to be minimized. Some of these byproducts can create microscopic inclusions that can affect the medical device fatigue performance.

In conclusion, to successfully manufacture Nitinol, one needs to be able to have very sophisticated processes and know-how that can homogenously control the nickel and titanium to an extremely precise ratio while minimizing the inclusion size to meet the rigorous medical device design requirements and comply with ASTM F2063. Downstream converters of the material then need to have processes and know-how to ensure these processes maintain the desired transition and inclusion specifications. Overall, it is a highly complex process that requires extensive industry knowledge—expertise that is hard to come by.

Fenske: Can you please speak to some of the concerns regarding the material’s availability? What are the challenges here?

Howe: There are a couple of key drivers that have made material availability over the last few years a challenge. First, as the medical device market came out of the pandemic, we saw significantly higher demand signal fluctuations. These demand fluctuations cause a bullwhip effect on supply chains that can impact material availability.

Additionally, the Nitinol supply chain is complex. To the casual observer, it may appear there is a single raw material made into a medical device. However, the reality is there is a large supply chain that spans a number of different independently owned companies, each with a role in getting the Nitinol raw material into the correct form factor to meet the ASTM specifications. Most of these independent companies have manufacturing lines that share Nitinol capacity with other alloys that support a number of different industries like defense and aerospace. As the demand in these industries has increased significantly in recent years, the available capacity for Nitinol is strained.

Confluent has been a pioneer of Nitinol since our founding as NDC over 30 years ago and recognized these challenges early on. Recent significant investments in the supply chain have ensured there is dedicated medical Nitinol capacity for our customers. You and your readers can learn more about these recent investments at Nitinol.com.

Fenske: What advantages are realized from working with a company that can provide both Nitinol materials as well as Nitinol components or sub-assemblies leveraging the material?

Howe: There are a number of advantages when working with a company that can provide a vertically integrated supply chain. These advantages mirror some of the challenges as noted in the previous questions.

A vertically integrated supplier is closer to the end user demand signal, which allows information to flow more smoothly and reduces any bullwhip effects when there are demand fluctuations. This allows the vertically integrated supplier to respond more efficiently, which helps keep costs down and reduce lead times.

In addition, when there are demand changes, particularly when increasing, a more vertically integrated supply chain is able to react faster to meet those demands. They can accomplish this without having to make costly inventory investments that ultimately tie up cash and add cost to the supply chain, which can affect the medical device part cost.

Further, by having a capacity capable of being dedicated to the fabrication of medical Nitinol raw materials, the risk of a supplier choosing to use their capacity for non-medical demand is mitigated.

Through Confluent’s partnership with ATI, the company now has the most integrated, dedicated medical Nitinol capacity throughout the entire supply chain. With this partnership plus previous investments, Confluent can now offer medical device companies improved lead times and more confidence in their Nitinol supply chain.

For example, Confluent is now offering four- to six-week lead times for production-ready qualification builds on tubing. Confluent also continues to offer industry-leading rapid prototyping lead times of two weeks or less.

In conclusion, the advantages of working with a firm like Confluent, which has invested heavily in a vertically integrated supply chain, include having a partner that can:

• Produce speed-to-market for Nitinol material with critical performance criteria
• Offer a supply chain that can scale and respond to changes in demand
• Provide industry-leading lead times of four to six weeks for production-ready tubing and two weeks or less for rapid prototyping

So from melt to component, Confluent is proud to partner with our customers to bring the Nitinol performance advantages to patients to help these companies save lives.

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