Tunnel Vision: A Roundtable Discussion of Tubing Experts
The desire for new catheter-based, minimally invasive treatments that can supplant surgical procedures is one of the key drivers of growth for the medical tubing market. The latest material technologies are being explored to improve physical properties, reduce processing costs, boost sterilization compatibility, and meet biocompatibility requirements.
As devices become more complex, medical device makers rely on tubing partners to simplify designs or consolidate parts. This can result in fewer points of failure, easier assembly, quicker regulatory approval, and ultimately lower cost.
Designers seek more physical properties from their tubing. One example is lower friction materials to promote softer durometers, higher tensile strength, recoverable elongation, optical clarity, and lower density. Some also look for specific straightness needs, burr-free end cuts, specific circularity, validation to dimensional, functional, and visual specifications, among others. And almost every device maker requests smaller, thinner-walled tubes with high tolerances and a balance of flexibility, strength, and lubricity.
In order to gain more insight on the trends and challenges for medical tubing providers, MPO spoke to these medical tubing experts over the past few weeks:
• Diego Aguilera, global account manager at Spectrum Plastics Group.
• Robbie Atkinson, CEO of MMT.
• Mark Broadley, tubing product solutions director at Viant.
• Kay DeWolfe, president of On Line Controls.
• Tim Finn, product development engineer at New England Tubing.
• Cody Flowers, senior development engineer at Teleflex Medical OEM.
• Christian Geppert, director of operations for Viant’s Aura, Germany-based tubing facility.
• Tim Hoklas, senior director of technical solutions at Viant.
• Sonia Schwantes, director of product management at NewAge Industries.
• Tim Steele, founder and CEO of Microspec Corporation.
• Mike Winterling, vice president of business development for the U.S. and Europe at Junkosha.
Sam Brusco: What are some of the most popular service requests for medical tubing you receive and what are the healthcare trends driving this?
Diego Aguilera: The most common inquiries we receive are for interventional, fluid management, and drug delivery applications. Devices and systems in these applications use a wide variety of tubing with various materials and configurations. The rise in vascular and respiratory diseases is one of the main drivers for this demand. Another is the increasing ability for patients to conduct treatments at home versus in-patient care. As devices become more portable and compact, the demand for disposable tubing increases. Home dialysis treatment is a good example.
Robbie Atkinson: The drive for expanding minimally invasive procedures is increasing demand for device miniaturization, meaning smaller tubing especially in the neurovascular, cardiovascular, and neonatal specialties. These modalities require transfer of more volume through a smaller space. To achieve this, customers need equipment that can effectively handle materials with a smaller diameter, thinner walls, tighter tolerances, and variable tube durometers.
Mark Broadley: Due to the trend for minimally invasive devices with advanced performance, we’ve seen interest in our precision laser-cutting and forming capabilities. We started our rapid prototyping facility in 2014 and have grown our business by more than 1 million feet each year since then. We’ve also seen a trend away from larger mechanically actuated devices—first-generation staplers and cutters—and growth in the smaller, energy-based devices. These smaller devices require smaller incisions resulting in quicker recoveries. In the implantable products we support, we are producing smaller and thinner cardiac stent tubes from exotic high-strength materials. In recent applications, these tubes support stents and delivery systems that allow radial artery stent delivery with much smaller incisions, fewer complications, and shorter recovery than the traditional femoral artery.
Christian Geppert: We’re experiencing increased pharmaceutical industry demand for drug delivery devices that can deliver medication precisely to maximize efficacy. Our Aura, Germany, facility specializes in stainless steel capillary tubes for soft-mist inhaler applications for COPD and asthma. Precision is key for these components, because even the smallest deviation from spec could compromise the device’s performance. Another popular service request is cleaning tubes to medical standards for cleanroom processing to remove particles and residue and reduce the risk of contamination. This is driven by the EU’s Medical Device Regulations (MDR) to avoid issues in the finished product.
Cody Flowers: Conductor-embedded tubing that provides a conductive path using alloy wires inside the tube’s wall. This type of tubing is constructed of either one insulation material or multiple material types (hybrids) with conductive wires within the wall. The reinforcement can be either coiled, braided, or linear. We find the ability to send and receive signals to and from the body and/or internal components is growing in demand as new technologies are developed.
Tim Hoklas: Customers are always looking to reduce cost. One way to do this is to leverage complex formed tubes to reduce the number of components in a device. We worked with a global OEM to transfer a complex, minimally invasive surgical device and combined two components into one complex formed tube—significantly reducing cost and achieving an estimated 45 percent savings.
Sonia Schwantes: We are still getting many requests for tubing for respiratory devices. With side effects from COVID, there is still a need even for those who are considered recovered. We are also seeing demand for tubing in surgical devices as people have begun rescheduling non-essential surgeries that had been put off.
Tim Steele: Everything we extrude is custom and very often the requests for quotation are for tubes or parts that push the limits of conventional extrusion technology. Whether the part is an ultra-thin wall tube, a multi-lumen, a bump extrusion, a tri-extrusion, or a combination of two or more, the parts we extrude can be difficult to classify as a generic tube. One tube we extrude has ten lumens, is a tri-extrusion, has two differently colored stripes, and has a 360-degree helical twist every 16 inches! What do we call this tube? We get requests for lots of very complex parts like this and that is definitely a trend we see that goes beyond making parts smaller, walls thinner, or dimensional tolerances tighter.
Mike Winterling: There is an increasing requirement for catheter manufacturers to improve efficiencies through streamlining workflows, which is transitioning from a “nice to have” to a critical requirement. Solutions like our 2.5:1 peelable heat shrink tubing (PHST) can provide catheter manufacturers with the highest shrink ratio currently possible in Peelable FEP thanks to proprietary material expertise.
Customers can stock fewer products and save time and money through a reduced number of shrink processes for complicated or tapered designs. In addition, thanks to PHST’s “take-up,” it allows for use of cost-effective, lower tolerance, baseline materials in manufacturing and provides the ability to reflow these easily into a single smooth construct. All this results in reduced total cost of ownership for the catheter manufacturer, enabling increases in profit margin per device.
Brusco: What new offerings and/or capabilities are available from tubing suppliers that medical device manufacturers do not yet fully embrace or realize?
Aguilera: Additive manufacturing (AM) is an important one; it lets R&D teams and designers bring complex tubing configurations to life at fractional development and manufacturing costs when compared to more traditional development options. AM gives device manufacturers the ability to quickly create and test complex prototype designs with several material options before taking their product to mass production levels. We have recently developed proprietary AM technologies for manufacturing high-precision, medical-grade tubing (single and multi-lumen tubing) that is not extrusion-based—a groundbreaking, industry-first capability.
Atkinson: Electrochemical grinding for burr-free metal tube cutting in needle and other medical device applications. Peelable heat shrink is also a new offering applicable to catheter manufacturing, which eliminates the need to cut away liners.
Tim Finn: Our eTubing solutions combine electrical and mechanical requirements in one tube, allowing component miniaturization and consolidation. We feel strongly this technology will become more commonplace in the industry as supporting technology develops.
Schwantes: There is still a lot of hesitation with new materials. We have seen growth in areas like biodegradable, nano, and smart plastics, but because materials like PE, PP, silicone, and TPE have so much history it can be challenging to understand where new materials will have a place in the market. Tubing seems simple but can be a critical medical device part and be further enhanced by the material chosen. Applying a new material can be scary but also a wonderful opportunity to bring new things to the table.
Winterling: Catheter delivery systems for neurovascular treatments rely on increasingly complex shapes, constructs, and polymers to deliver treatment. This intricacy in catheter bonding and welding applications can only be consistently achieved through advanced technology innovations like 2.5:1 shrink ratio PHST. This high shrink ratio enables catheter manufacturers to use different diameters within a device, ensuring a wider range of technology options. It can also further allow complex shapes and constructions. Key application areas include balloon mounting, catheter lamination, forming, tacking, masking, bonding parallel tubes, and polymer jacket compression.
We also see increasingly sophisticated or “intelligent” catheters that can send diagnostic signals into the body or provide therapy. The journey toward intelligent catheters is important—it is crucial to have smaller, more flexible catheter-based devices with higher signal capacity to advance surgery. Solutions like our Multi-Filar Cable and Junkosha Multi-Channel Transmission Cable (MCT) represent a breakthrough in the size reduction of tubing-based diagnostic and/or therapeutic medical device cables.
Brusco: Which materials do you use to manufacture medical tubing, and what benefits do they offer end-use products?
Broadley: Nitinol—a super-elastic material with a very high ability to stretch without breaking—continues to be extremely popular. Our primarily application is for peripheral stents used outside the chest area, so they’re less protected. They must hold their shape against any force, like bumping your leg against a chair. A nitinol stent can be crushed completely flat and it springs back to its original shape, serving a need in peripheral vascular applications that can’t be met with standard materials. However, nitinol is costly and difficult to join with other materials. Many times with nitinol devices, most is spent in the total device’s length. It could be 20 inches long, but only two require nitinol’s flexibility of nitinol. There’s a need to replace most of the nitinol with stainless steel by somehow joining them in the same device.
Finn: Pebax and polyurethane are by far the most common. I believe it’s due to their performance, biocompatibility, and their recognition in the industry. Both materials are available in various durometers ranging from extremely soft to very hard, which makes it easy to customize a device to customer requirements.
Flowers: Our main material is polyimide, a standard material for high-strength products requiring micro-diameters and ultra-thin walls. PTFE and our PD-Slick materials offer a lubricious coating for composite tubing or mandrel-wire. PTFE is widely used for this case, but PD-Slick offers a slightly less lubricous alternative, which is more compatible with medical device manufacturing and sterilization techniques. We also offer Pebax and nylon-based outer-diameter coatings. These materials improve thermal bondability and flexibility when applied as a topcoat for polyimide.
Geppert: In addition to standard stainless steels, we use MP35N (nickel-cobalt alloy) for high-pressure liquid chromatography applications. It has extremely high tensile strength, high flexibility, and is ion-free. Elgiloy (cobalt-chromium-nickel-molybdenum alloy) has extremely high tensile strength, is ion free, and may be substituted for materials with higher cobalt content in EU medical device applications. L605 (cobalt-chromium-tungsten-nickel alloy) has high tensile strength and high elongation in stent tubing applications. Monel (nickel-copper alloy) has high flexibility during manufacturing for more complex geometries.
Hoklas: Our materials experts can modify chemical compositions to achieve different mechanical properties. An example is 304HS stainless steel: Customers with space constraints on ID or OD requirements can achieve better strength with a thinner-wall tube with 304HS than standard 304 stainless steel. 304HS meets all the chemistry specifications of standard 304 stainless steel—selecting different elemental concentrations in the specifications allows the improved properties.
Winterling: We possess a deep understanding of high-performance polymers, particularly in fluoropolymers such as perfluoroethylene propylene copolymer (FEP) and polytetrafluoroethylene (PTFE) that are at the heart of our key products. We were the first company to add ease-of-peelability to traditional FEP heat shrink tubing, enabling higher throughput, improved quality, and fewer ergonomic issues. The fundamental structure of these materials exhibit a myriad of benefits, including:
excellent biocompatibility for patient safety;
low coefficient of friction to pass a catheter over a guidewire or passing a device through the inner lumen of a catheter;
high temperature resistance to maintain mechanical integrity during different manufacturing steps such as lamination; and great chemical stability, which enables development of a wide range of processing conditions and end uses.
Brusco: How has the trend toward miniaturization of medical devices impacted tubing development and/or customer demands you receive?
Atkinson: For polymer tubing used in catheter-based applications, the constant push for thinner wall and lower durometer materials can prove difficult for precision cutting and drilling. The SYNEO Accu-Cut and Accu-Drill solutions and tooling are specifically designed to provide the best results for these challenging materials. For burr-free cutoff and grinding of metal applications, Tridex equipment can cut smaller tubing and hold more accurate tolerances than ever before. Tolerances of +/- .001” (0.025mm) and cut lengths as short as .118 (3mm) on tubing as small as 31 gage (.010” diameter) are now achievable. Cutting such small parts without burrs is a huge cost savings due to the elimination of secondary processes.
Kay DeWolfe: Tubing miniaturization has required more air pressure units in lower and lower ranges. Some tubing extruders now use air pressure below an inch of water and more multi-channel units for multi-lumen tubing. The newest requests have been for multi-channel units with a wide range of pressures from zero to three inches of water to 0-3 psi in the same unit to make various size holes in the tubing.
Finn: Customers constantly push the limits on what’s possible, consequently pushing advances on our in-house machine shop to utilize new manufacturing techniques. It’s a benefit of being vertically integrated that we can have rapid turnaround times for tooling development runs. It allows us to fine tune the tooling to meet exacting requirements and tolerances.
Flowers: We see more requests for smaller, thin-walled tubing. The trends seen in medical devices are pushing us to find solutions for smaller, more complex composite structures. Our process utilizes a unique film coating process to meet these demands and fill the gaps between discrete-length dip coating and extrusion.
Steele: Miniaturization has made extrusion process validation very challenging. As the tubes or parts get smaller, so do dimensional tolerances, making process capability more difficult to demonstrate.
Today it’s common to see dimensional tolerances of plus or minus +/-.0005”. To meet a CpK of 1.33 the extruder must maintain +/-.0003”, which is not an easy task. Miniaturization also challenges quality inspectors. A question we often ask before making a new miniaturized part is “how are we going to measure and verify dimensions?” This drives inspection equipment manufacturers to innovate and build equipment suited to reliably measuring parts with micron-level dimensions.
Schwantes: We always look for areas to add capability and as medical devices become smaller, more is being asked of extrusion. We make sure to focus on areas where we can become experts, and we know sometimes we can’t meet all the needs out there. We have carefully selected areas where we can bring value and work toward providing more options on the smaller end of tubing sizes.
Brusco: How will tubing manufacturing change over the next five years?
Aguilera: Tubing will continue to be a key element in medical devices, but there will likely be a convergence of requirements to meet the industry’s evolving needs. As engineers look to develop smaller, more capable devices, the requirements will increase for expectations of each component in a device. As supply chain teams look to mitigate raw material availability and supply chain risk, they will push for parallel validations of alternative materials that can meet the same performance criteria. As corporate initiatives focus on improved sustainability in single use devices, there will be a focus on material content optimization and sustainable material grades. These technical, supply chain, and sustainability objectives will require more alignment and optimization on the total value of a program.
Atkinson: We will see an increase in the acceptance to “lights-out automation.” Tube manufacturers will also offer integrated secondary operations—for example, extruders will add cut-to-length and hole forming. This equipment will need to communicate in automated production lines. As tubing precision requirements continue to increase, machine developers will incorporate closed-loop feedback control systems as well.
Broadley: Metal tubing will continue to be an ideal material choice for strength, cutting-edge retention, or elevated temperature performance. Expect to see focus on advanced performance and adapting design and manufacturing processes to optimize performance. We will likely see more specialized device needs, leading to smaller lot sizes. The supply chain issues we’ve recently experienced will also focus our efforts on shortening supply chains and driving growth in “local for local” markets instead of worldwide sourcing.
DeWolfe: We see a lot of multi-lumen tubing with both wires and tubes so only one incision has to be made for most surgeries. A lot of the tubing now used for medical devices will continue shrink as machines are downsized.
Finn: Multi-durometer tubing will be utilized more as designers’ demands push for the pinnacle of performance in the medical industry. The ability to have both pushability and torque response in a very flexible tube at the distal portion is highly sought after.
Flowers: In our market specifically, the trends point to smaller, thinner walled tubes with a balance of flexibility, strength, and lubricity. We also see increased demand for thin-walled tubing in the ID size range of 0.100”-0.325”, specifically outside of the current limits of extrusion-based processes. We expect to see new technologies and manufacturing methods to achieve these specialty builds.
Geppert: In the EU, there will be substitution of cobalt-based alloys because of regulations. Having a thorough knowledge of increasingly complex regulations will become a unique selling point, as well as a value-added service to the customer. Also expect there to be increased speed to market to better support new product introductions. More specialized and more complex products will drive smaller lots, requiring a change in manufacturing processes and partnerships with customers.
Schwantes: Extrusion will be further pushed to create smaller, more complex tubing but we may see a change in requirements as medical device and biopharma converge. Combination products may develop new requirements for tubing because it’s integral to delivering a drug directly into the body with devices like personal pumps.
Steele: I’ve been in medical extrusion since 1976, so I’ve seen a lot of change. Looking back, the biggest change I’ve seen is how complex medical extrusions have become and the number of companies now making these parts. Going forward, I see this trend continuing. In recent years there has been a lot of vertical integration of larger companies acquiring smaller or not-so-small extrusion companies to offer more complete OEM services. It used to be that most innovative medical extrusion was done in the U.S. I expect that to change as I see development of medical extrusion happening in a big way in China, India, and across Europe, with many new players. I think the growth we’ve seen in recent years will pick up and we can expect over 20 percent growth from year to year. During the pandemic medical extrusion production was flat but new product development was strong, indicating we can expect to see a lot of new technology launched in the next five years.
Article source: Medical Product Sourcing