By Sean Fenske, Editor-in-Chief

Trends in healthcare have device manufacturers searching for ways to meet growing needs. Two driving forces are minimally invasive procedures and miniaturization. As a result of this environment, devices are getting smaller so they can be placed within the body, closer to the areas in which they are required. Getting these advanced solutions to those locations, however, is a significant challenge.

Catheter-based delivery systems are becoming more advanced to facilitate the transport of these devices to critical areas of the body. To ensure success, however, the inner lumens of the catheters must provide an untrammeled pathway from one end to the other. As such, medical device manufacturers are seeking answers from those involved with catheter manufacturing to benefit from their offerings and expertise.

Providing insights on the advantages of using PTFE liners within the development of such catheter systems is Mike Winterling, Chief Operating Officer at Junkosha USA Inc. In the following Q&A, he explains what the liners are, their purpose, and what potential buyers of this technology need to keep in mind. He also shares his expertise on heat shrink tubing technology, which can also be used in catheter fabrication.

Sean Fenske: What are etched PTFE liners? What do they do and why are they used?

Mike Winterling: Etched PTFE liners are the unsung heroes of catheter design, transforming the way medical devices can be introduced through a catheter to the location of the therapy. These liners serve as the inner layer, or lumen, of the catheter, creating an ultra-slick, low-friction highway for tools and devices to glide through with ease. Thanks to the naturally lubricious properties of PTFE, they are an excellent material choice for catheter lumens.

The etching process provides a chemical and physical change to the outer surface of the liner, allowing for a robust and consistent bonding of layers during the lamination process. Junkosha Etched PTFE Liners utilize a precisely controlled etching process, delivering a consistent adhesion of layers during processing, which allows manufacturers to achieve higher yields and throughput.

Fenske: What benefits do they provide? How do these differ from comparable products on the market?

Winterling: Compared to dispersion PTFE liners, extruded liners offer greater tensile strength and mechanical robustness, allowing the passage of devices such as self-expanding stents or embolic coils. Extruded liners are typically used in a batch process, which allows considerable design freedom such as segments of different durometer jacket materials, or varying the reinforcing braid or coil being utilized. The process begins by stretching the liner over a processing mandrel; extruded liners allow the use of tapered or stepped mandrels for further design flexibility. Junkosha’s PTFE processing expertise allows control over critical mechanical parameters such as yield point and elongation to help optimize the catheter production process.

Fenske: What considerations should be kept in mind when selecting these? Are there limitations or instances where they shouldn’t be used?

Winterling: PTFE is a unique material that is processed with paste extrusion rather than melt processing. If the process is not controlled well, there can be inconsistency in elongation and tensile strength, leading to a poor bond and breakage during the catheter manufacturing process. The thinner the wall thickness and the greater the amount of stretch in the process, the more important the control of the mechanical properties of the liner.

In terms of limitations, the use of extruded liners is probably not necessary for less demanding applications such as access or embolization catheters, which can be produced in a continuous process and do not require passing stents or embolic coils through the inner lumen.

Fenske: What do customers typically look for in liners? Why?

Winterling: Many of our customers are pushing the limits on the overall size of their devices as well as improving the trackability of their products to treat a wider range of patients. As a result, these efforts often include requests for thinner and tighter tolerance materials that still maintain the mechanical integrity, trackability, and performance required of the finished device. For the liner, the challenge is becoming thinner while still maintaining excellent burst pressure, tensile strength, and good yields in the manufacturing process. Junkosha continues to push the limits of its processes, as well as regularly analyzes ways to innovate and keep up with future trends.

Fenske: Junkosha also provides a peelable heat shrink tubing product. What is this and what benefits does it provide?

Winterling: Heat shrink tubing has long been a staple in the catheter assembly process, playing a crucial role in reflowing materials. Many medical device manufacturers think it is difficult to use heat shrink tubing for micro-catheters, mainly due to the challenge of using razor blades to skive and remove the tubing after the reflow process. However, Junkosha Peelable Heat Shrink Tubing solutions make this a possibility, simplifying the manufacturing process with a convenient and efficient peeling design. Peelable heat shrink tubing allows OEMs to easily remove the tubing without having to shave or cut away the material, as is often required with traditional heat shrink tubing. Whereas skiving is difficult for operators to complete, peelable heat shrink is simple to learn how to use—saving time and reducing costly scrap rates.

Fenske: For what types of applications is this used, and where shouldn’t it be used?

Winterling: Junkosha Peelable Heat Shrink Tubing is used across a wide range of applications. It is often used for smaller devices like microcatheters as these devices are more fragile and benefit from easy peeling forces. It can enable tapered or other complex-shaped devices where skiving tools are impractical to use. It also provides benefits for devices with jackets that vary in diameter, since the depth of skiving can be difficult to manage in that situation. We offer a comprehensive range of diameter and shrink ratios to support applications ranging from small devices, such as microcatheters, to larger devices, such as peripheral vascular or structural heart. By controlling the shrinkage force and elongation characteristics, as well as minimizing the force to peel, we can help optimize your manufacturing process to deliver consistent quality.

There is almost always a benefit in using peelable heat shrink, with increased throughput rates, increased yield, and improved ergonomics for the manufacturing operator. If you are facing challenges with yield rates, injuries with operators, or want to increase throughput rates, consider trying Junkosha Peelable Heat Shrink Tubing.

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?

Winterling: At Junkosha, we pride ourselves on developing innovations that address customers’ unmet needs. As increasingly intricate procedures become viable, medical devices will become smaller and more complicated. We have a deep heritage in materials science and fluoropolymers, which means our solutions are at the leading edge of what is possible. Junkosha is committed to being the best long-term partner by working together with customers to not only meet their unique requirements but also provide solutions aimed at significantly improved yields and reduced catheter manufacturing costs.

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