By Sean Fenske, Editor-in-Chief
 
When a medical device manufacturer needs reinforced tubing, they may be concerned with the interior diameter, exterior diameter, length, plastic material, or other specifications. They may not, however, give as much thought to the actual wire used within the tube wall to enable the reinforcement. The wire that’s used for reinforced tubing, however, is just as critical a consideration as the tube itself.
 
Potentially even more significant is the wire used as part of a finished medical device, such as transcatheter technologies. For this type of product, the wire plays a more “active” role in the actual delivery of care, carrying a stent, valve, or other life-preserving technology to a location deep within a patient’s body. The wire must perform as required and, as such, must be developed to exacting standards.
 
Assisting device makers with these challenges is Ulbrich Specialty Wire Products. Both Ed Treglia, vice president/general manager, and Ryan McFarland, product manager, took time to speak with MPO about the many variables involved with identifying the right wire for an application. They offer insights on materials, shapes, and their impact on different applications.
 
Sean Fenske: When we’re talking about specialty wire for medical device manufacturers, what are we talking about specifically?
 
Ryan McFarland: Specialty wires are those that are developed specifically for an application, as opposed to commodity-type wires that are mass produced with limited regard to how they could enhance performance in the end use. It’s the difference between a purpose-built product and more of a one-size-fits-all product. At Ulbrich, we specialize in tackling the challenges that our customers face and provide them with a highly specialized product that meets the demands of their manufacturing processes and end-use application.
 
Ed Treglia: To add to that, effectively producing specialty wire for medical devices requires capable human technical resources who remain focused on serving the unique needs of the end application. It also requires specially designed equipment for all processing steps, including hot and/or cold working, thermal treatment, plating or coating, and precision winding.
 
Fenske: How is wire used within medical tubing and what benefits are realized?
 
McFarland: The two primary types of wire that are used to produce medical tubing are mandrel wire and braid-reinforcement wire. Silver-plated or bare-copper mandrel wire is often used as a tool to form the tube.
 
Manufacturers of braid-reinforced medical tubing require extremely small “ultra-fine” wires that possess precisely controlled dimensions, properties, and winding so they can successfully produce consistent product. Therefore, high levels of precision in the wire manufacturing are critical.
 
Treglia: Those precisely controlled dimensions and concentricity of the mandrel wire enable highly accurate tubes to be produced over it, as the dimensions of the tube ID will be exactly that of the OD of the mandrel over which it is formed. This tube production technique also requires that the mandrel have a carefully controlled surface finish quality.
 
Braid reinforcement wires are typically extremely small, round or flat, stainless steel wires that are braided over the tubing to give it burst strength, torque transmission, column strength, etc. In special cases, tungsten wires are used to enable increased strength and/or radiopacity of the braid. Other metals or alloys can be used to achieve special properties or characteristics. An overcoating is typically applied over the braid layer, which fully encapsulates the braid. The mandrel wire is eventually stretched and removed from the inside of the tubing.
 
Fenske: What are the differences between braid, coil, and mandrel as it relates to medical tubing and catheters?
 
McFarland: Braided and coiled wires are both used to reinforce medical tubing. Coil reinforcement is typically used to improve kink resistance, while braid reinforcement is used when torque transmission and burst strength are also required. Coil wires are helically wound, resulting in different physical characteristics and behavior of the tubing than with braiding, where wires are crossed over one another. Mandrel wire is used as a tool to form the inner diameter of the medical tubing and is not part of the finished product.
 

Fenske: When manufacturers are developing transcatheter products, what must they keep in mind as it relates to the wire component?
 
Treglia: Most medical manufacturers need to consider a vast amount of information about the procedures to be performed when manufacturing their components and devices. The number and complexity of medical procedures performed with transcatheter techniques has grown significantly in recent years. The pace of development of new medical procedures and technologies continues to expand and evolve. This has led to manufacturers also needing to keep expertise, technology, and innovation in mind when working with the wire component of the parts they produce.
 
McFarland: In addition, specialty wire is an integral component needed to produce most of these devices, and in a multitude of ways, can enable rapid, precise, and uniquely designed life-saving devices.
 
Ulbrich’s Development Partnership puts medical device design engineers directly into contact with our wire making experts, enabling effective development of a highly customized wire solution for their device. Our Braid Wire Accelerator™ Program can put wire into the hands of the development engineer within just a few days.

 
Fenske: In what other types of medical devices and applications is specialty wire used?
 
Treglia: The beauty of specialty wire is its versatility. There are a wide range of devices and applications that benefit from wire produced with highly precise characteristics, dimensions, and properties. It is an integral part of many types of delivery systems, devices, and implants. Examples include catheters, coils, stents, guide wires, electrophysical and endovascular device components, etc. Specialty wire engineers are an indispensable resource for medical device designers when it comes to materials selection, design, and development of novel devices, components, and implants.
 
Fenske: What additional advantages does specialty wire offer that manufacturers don’t realize, such as shapes that can be formed and/or the use of multiple types of metals to achieve a certain effect?
 
Treglia: Specialty wire comes in an infinite number of potential shapes, sizes, combinations of materials, and properties. The most common shape is a round wire, but flat wire is also commonly used. Shaped wire, with a symmetrical or asymmetrical profile, can be employed in cases where a special geometry will be more effective.
 
McFarland: Regarding material options, wire produced from metal alloys is the most common type. An alloy is a combination of metals that are melted together, oftentimes with small amounts of non-metallic elements. 304V stainless steel is an alloy made up mostly of iron, nickel, and chromium, with several other elements in smaller amounts. After melting, it is vacuum remelted to remove impurities, helping enable it to be transformed to the extremely small shapes and sizes that are needed in medical devices. Nitinol is an alloy of nickel and titanium, possessing shape-memory and super elastic properties, which is used in a multitude of medical devices and implants.
 
Oftentimes, a combination of properties that is impossible to achieve with a single metal or alloy are desired. Wire consisting of distinct layers of completely different metals or alloys can be used to achieve properties that are uniquely tailored for the device. Cladded wire enables properties that cannot be achieved with a single metal or alloy alone. A couple of examples are electrical conductivity combined with biocompatibility, and shape memory combined with radiopacity.
 
Fenske: Do you have any additional comments you’d like to share based on any of the topics we discussed or something you’d like to tell medical device manufacturers?
 
Treglia: Clearly, medical device designers and manufacturers continuously face an immeasurable number of challenges and opportunities in carrying out their work. Collaborating with subject matter experts in designing, developing, and producing their devices is a sure-fire recipe for optimizing success.
 
Ulbrich’s Development Partnership program has been built to facilitate effective collaboration when it comes to specialty wire components. Our team of engineers, academic partnerships, and industry experts have worked on countless difficult projects with our customers to help them overcome challenges in producing their product. From difficult to manufacture items to ground-breaking innovations, our expertise in materials science and engineering coupled with specially developed processing capabilities and measurement/testing and quality control systems are invaluable tools that can be enablers of leading-edge advancements and sustained product performance for medical device manufacturers.

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