Engineering the PFAS-Free Future: UHMWPE as a High-Performance Alternative to PTFE Liners
Chapters:
00:00 Welcome
03:16 Sponsors and Speaker Introduction
05:50 Why the PFAS Conversation Is Accelerating
09:59 UHMWPE as a PFAS-Free Alternative
14:02 Mechanical Behavior, Creep, and PTFE vs. PFAS Clarification
18:10 Reflow, Surface Roughness, and Lubricity Data
25:45 Selection Criteria, Wall Thickness, and Scratch Resistance
31:25 Dielectric Strength and Surface Activation
40:32 Sterilization, Shelf Life, Regulation, and Sustainability
50:23 Audience Q&A and Closing Remarks
00:00 Welcome
Katie Karmelek
Good morning, good afternoon, wherever you’re joining from. Thanks for being here, and welcome to today’s webinar.
Engineering the PFAS-free future, ultra-high molecular weight polyethylene as a high-performance alternative to PTFE liners. I’m Katie Karmelek with Chamfr, and I’ll be your moderator today.
Before we get started, we have a few quick housekeeping notes.
This session is being recorded, and the recording will be shared with all registrants. All attendees are muted, and chat is disabled, but please use the Q&A. You’ll see a Q&A button at the bottom of your screen. We really want to hear from you, and we want this to be a conversation that’s valuable for everyone.
We’ll address as many as we can during the webinar, but also have some dedicated time at the end as well.
To keep things interactive, we’re also going to have a few quick polls sprinkled in along the way. It’ll be quick for you to just pick a multiple-choice question on your screen.
03:16 Sponsors and Speaker Introduction
Katie Karmelek
Before we dive in, I do want to take a moment to thank today’s promotional sponsors. First, we have ICS Medical Devices. They’re based in Galway, Ireland, and are redefining what’s possible in catheter shaft technology for minimally invasive devices.
ICS delivers solutions where performance, flexibility, and control aren’t a compromise, they’re a given. And you can even find their steerable catheter shafts available in stock, ready to ship on Chamfr today. Check out that QR code there on the screen, and we’ll show it to you again later toward the end.
Our second sponsor. That’s LightningCath. They’re a component-focused catheter manufacturer specializing in extrusion, design, and assembly solutions for interventional devices.
Their core capabilities include extruded tubing, FEP heat shrink, PTFE liners, balloons, and rapid catheter development. You can shop FEP heat shrink and Pebax extrusions from LightningCath on Chamfr right now.
Same QR code at the bottom. But now I’d like to introduce our featured speaker today.
Cheng Wei is a senior scientist and application expert with the biomedical group at dsm-firmenich, based in the Netherlands. He brings a decade of experience at DSM Biomedical, where he has played a key role in advancing high-performance polymer solutions for medical devices.
Cheng Wei has an exceptional academic background. He holds a PhD in polymer physics from the Max Planck Institute for Polymer Research, where he graduated summa cum laude. He also earned a master’s in physical chemistry and earlier degrees in polymer engineering and international economics. In addition, he completed executive education at IMD and an MBA from the Rotterdam School of Management, giving him a unique combination of deep technical expertise and strategic perspective.
Today, Cheng Wei is the dedicated technical expert for material science, and specifically UHMWPE applications, and plays a central role in translating material innovation into real-world device performance for next-generation interventional technologies. Cheng Wei, it’s great to have you with us.
Cheng Wei
My great pleasure to join you, Katie, and also my regards to the participants online.
Great to join you. Hopefully we can have a very great conversation together.
Katie Karmelek
Absolutely.
05:50 Why the PFAS Conversation Is Accelerating
Katie Karmelek
Before we dive into the material science, which I know everyone here is really excited to get into the deep technical, let’s ground this conversation in why it’s happening now. There’s been a lot of back and forth around PFAS, right? Changing regulations, growing concerns, and what it all means for fluoropolymers in MedTech.
And it’s hard to know what the actual requirements are and why it matters. For years, the industry has operated under a reasonable assumption that fluoropolymers, like PTFE used in catheters and delivery systems, are fundamentally different from the PFAS compounds making headlines in our cookware and whatnot. And that’s true.
PTFE is a large, stable polymer, and the FDA has reaffirmed it’s unlikely to pose patient toxicity risk, even as recently as last year.
They confirmed that there are no equivalent materials for many applications. So from a patient safety standpoint, PTFE really isn’t the problem, right? But the challenge isn’t inside the device, it’s upstream.
It’s manufacturing processes, it’s supply chain challenges, and also the regulations are changing. It’s confusing. We’ve got EU regulations that are different than FDA. So the real question isn’t, should we stop using PTFE today? Because for most applications, the answer is still no. PTFE is a very viable solution.
But the real question is, what does your material strategy look like three to 10 years from now? And that’s exactly what we’re here to talk about today. So, Cheng Wei, from your perspective working daily with biomaterials, why is the PFAS conversation accelerating now, and specifically in vascular device development?
Cheng Wei
Thank you, Katie, for the question. I think you already put the PTFE concern there, the PFAS concern, and I also agree with you that it’s a little noisy. On the one hand, the FDA does not really restrict PTFE use and also does not consider PTFE as a health threat when used in medical devices. On the other hand, we also see some other noise.
I would just say, in general, there are two forces. One is regulatory pressure. The other is supply chain security.
The FDA’s position does not necessarily mean that PFAS concern is not with PTFE, because we also have an EPA in the United States.
So actually, the PFAS concern around PTFE, as you said, is never about its safety in the human body. It is really about the environmental and health risks associated with the small-molecule PFAS substances that are used or generated during the manufacturing, processing, and even disposal of PTFE, and that is a concern.
As you also mentioned, in Europe, the regulation seems stricter, and as far as I know, regulators in Europe are really moving toward broad PFAS restrictions, which could have a high chance to impact medical devices. The EU is evaluating nearly complete PFAS bans, with only limited exceptions for essential use. I think that forces medical device companies to either proactively justify or replace PTFE-based components.
Supply chain is also another concern, because as industries outside healthcare move away from PFAS, the overall global supply and demand landscape of PTFE is changing. This could pose a significant risk to PTFE supply security in the medical device industry. I think all these factors, adding up together, still make this PFAS discussion very important around PTFE.
Katie Karmelek
Thank you for that. Really appreciate your insights into why this is so important, because I don’t know about everyone else, but I’ve been really confused. We have to get rid of all PTFE, no, we don’t, and it’s been really confusing, so thank you.
09:59 UHMWPE as a PFAS-Free Candidate
Katie Karmelek
We’re going to kick this off by actually getting a quick pulse of the room before we go any further. So we’ve got three polls today. The first one is really for the engineers on the call, but everyone can answer.
I am going to launch this poll right here.
And hopefully everyone can see that. We are asking, what technical questions are you still facing when using PTFE?
Is it wall thickness limitations, you’re unable to achieve thin enough walls, difficulty finding suppliers that can meet required specifications, concerns regarding PFAS regulations or future restrictions, or performance trade-offs such as flexibility, bonding, or durability issues?
While everyone’s answering, Cheng Wei, when I was an engineer designing minimally invasive medical devices, we always picked PTFE because that’s what we knew. We knew it gave us the lubricity we needed, and it was known, right? And there really wasn’t a material that we understood that could even come close to the performance. So I’m curious to see if folks on the line here today have that same viewpoint.
Cheng Wei
Me too, I’m also very curious to see. I’m also really curious to learn from them, actually, because I’m not really an engineer. As you know from my background, I’m a scientist.
Katie Karmelek
Excellent. Well, I will conclude the poll now, and I think it’ll show everyone on the screen the answers, I believe. And it looks like over 50% of folks are concerned with the PFAS regulations and future restrictions, which is great to know, because that’s really a big part of the topic that we’re going to discuss here. But also performance trade-offs, flexibility, bonding, and durability issues. That was great. Thank you, everyone, for participating in that. There’ll be two more throughout.
But given all these pressures, Cheng Wei, we’ve got regulatory, we’ve got supply chain, we’ve got environmental concerns, we’ve got mechanical performance. How is DSM Biomedical approaching this challenge, and where does UHMWPE fit as a real alternative to PTFE liners?
Cheng Wei
Actually, our solution for PTFE, or PFAS-free, is UHMWPE, ultra-high molecular weight polyethylene.
It’s not because we work on ultra-high molecular weight polyethylene that we think it’s a good fit. Actually, I think this is a pure coincidence, because this material, from a chemical perspective or from a structure perspective, does bear some similarities to PTFE, as you can see from the chemical structure, right? Both molecules have this linear carbon-carbon backbone.
So that’s the same for PTFE and UHMWPE. Only in one case, the side atoms are hydrogen atoms, and in the other, fluorine atoms. Because of that difference, of course, they are different chemical species and they have different properties, but on the other hand, they still bear quite some similarities.
For example, ultra-high molecular weight polyethylene is also very chemically inert, biocompatible, and has a low coefficient of friction, actually second only to PTFE among all polymers. So this already gives this material a very good position in replacing PTFE.
In addition, this material also has a very long clinical history, well established. That gives it an easier path for regulatory approval. So that’s why we think this is a great material for replacing PTFE. But of course, we still need to explore together with the whole industry. I think that’s also the reason for the whole webinar. It’s not there yet, but we think this is a very good candidate.
Katie Karmelek
Excellent. I didn’t realize the molecular structure was so close, so that’s really interesting.
Cheng Wei
Yeah.
14:02 Mechanical Behavior, Creep, and PTFE vs. PFAS Clarification
Katie Karmelek
PTFE is famously described as soft, despite its durometer. It deforms under sustained compressive load at room temperature, which engineers have actually learned to design around.
How does UHMWPE behave under that same sustained load? Is it more dimensionally stable, or does it introduce different deformation characteristics?
Cheng Wei
Actually, UHMWPE holds its shape much better than PTFE, because its chains do not slip as easily.
PTFE actually has a fully fluorinated carbon-carbon backbone, as we can see from the screen, from this space-filling molecular model. If you see this right chain, actually it’s PTFE. You hardly see any carbon atoms. They’re all shielded by the big fluorine atoms.
So this gives a very low intermolecular friction between the chains. So when PTFE is under pressure, its molecules tend to slide past each other, which shows up as cold flow, or easy creep, on a microscopic scale.
But UHMWPE is different. If you look again at this molecular model, its carbon-carbon backbone is not fully shielded by the hydrogen atoms. You can still see the carbon atoms and the carbon-carbon backbone. So in this case, the intermolecular friction actually is higher. In addition, for UHMWPE, its chains are more flexible, which generates a much higher entanglement density in the system. So all these factors actually give a much higher barrier for the chains to move under load.
So, in practical terms, PTFE tends to creep and deform under sustained compression, while UHMWPE actually keeps more dimensional stability. We can see this from the structural difference.
Katie Karmelek
Interesting. There was actually a question when we were talking about the background of PTFE and PFAS regulations, so I do want to circle back to this before we get too deep into the UHMWPE side. We have an audience member that would like to clarify the difference between PTFE and PFAS.
Could you elaborate on that a little bit, Cheng Wei, please?
Cheng Wei
PTFE belongs to the PFAS family, because PFAS means per- and polyfluoroalkyl substances. Actually, it represents a very large family of more than 10,000 chemical species that are fluorinated, including both small-molecule PFAS and large-molecule PFAS like PTFE.
So that is actually a very brief answer. Indeed, PTFE belongs to the PFAS family. But, as I also mentioned earlier, the real concern for PTFE is not about this macromolecule itself. It’s safe, but it does not degrade in the environment. On the other hand, making it actually uses some smaller PFAS substances, and those are toxic, and that is the concern.
Katie Karmelek
And those are the PFOAs, the chemicals that help the manufacturing of it, right? And those are concerning. Even if they’ve eliminated some, the ones they’ve replaced them with are also equally concerning. Is that correct?
Cheng Wei
I think so, because all the smaller PFAS molecules, even if you move away from PFOA or PFOS, those molecules persist in the environment. They don’t go away, they don’t degrade. That will always generate an environmental health concern.
Katie Karmelek
Thank you. Really appreciate that.
18:10 Reflow, Surface Roughness, and Lubricity Data
Katie Karmelek
So, when we think about circling back to the chemical structure of UHMWPE, it does seem to have similarities, but some of the differences are actually in favor of mechanical performance.
How does that behavior change at temperature ranges? Maybe we think about reflowing this into a catheter, or maybe impacts of temperature from sterilization. Does that molecular structure and behavior change from temperature range exposure?
Cheng Wei
That’s a really beautiful question, actually. This also reflects a very big difference between these two molecules. We know that PTFE has a very high melting temperature. In Celsius, it goes above 340, and ultra-high molecular weight polyethylene is much lower. It’s only in the range of, let’s say, 130 to 140, or even a bit lower in this range.
However, this does not mean that we cannot do catheter reflow using UHMWPE. And here’s why we need ultra-high molecular weight. We would like to have a high melt strength, and that can be given by its extremely high molecular weight, the long chains of UHMWPE, not ordinary PE. Because with ordinary PE, you don’t have that higher melt strength, and you also do not have the kind of entanglement needed to give this molecule its superior properties.
So despite the fact that during reflow UHMWPE does melt, because its melt does not flow easily, it behaves more like a gel or rubber. That’s why it can keep its dimensional stability and uniformity during the reflow process.
Katie Karmelek
Interesting.
What about surface texture? PTFE’s paste extrusion creates what some engineers describe as a molecular-level orange peel, like a microscale surface texture that may actually contribute to its lubricity.
How does UHMWPE’s surface morphology compare? Does it require engineered texturing or surface modifications to replicate that effect?
Cheng Wei
First I can share my own thought on this. I think PTFE has a very low coefficient of friction. The number one factor is not due to roughness or whatever, it’s really due to the molecular nature of this molecule.
If we want to compare the surface roughness of a UHMWPE liner with a PTFE liner, we first need to clarify a subtle but very important point, which I already briefly mentioned.
We can talk about the surface roughness or surface morphology of a PTFE liner as an independent component, because PTFE retains its solid state during the reflow step.
So this means the original surface morphology, for example after paste extrusion, is largely preserved after reflow. So what we measure finally from the lumen surface is essentially the same surface that the PTFE liner had before assembly.
However, this logic does not apply to UHMWPE. UHMWPE melts during reflow, because typical reflow temperature is way above the melting temperature of UHMWPE.
That means any original morphology will be erased, and the ultimate surface roughness is not determined by the initial liner surface texture, but by the detailed reflow and cooling conditions.
And this is a bit subtle. However, this is something we have to be really clear about, the essential difference between these two materials.
Coming back to your question, we did measure the surface roughness of our own UHMWPE liner and a commercial PTFE liner, and the results show that the UHMWPE liner is a bit rougher.
This can be explained by the detailed or typical reflow and cooling conditions, plus some polymer physics knowledge. So this can be explained. However, in that respect, I would say there’s no extra need to do texturing or surface modification to further enhance its roughness, because it’s already rough enough, at least compared with a typical PTFE liner surface. But whether this roughness in the UHMWPE liner is beneficial or not, honestly, I don’t know.
When it’s compared with a hypothetical ultra-smooth UHMWPE surface, I don’t know. I think this is still an academic question. Some fundamental research along this line would be very helpful.
Katie Karmelek
Okay, and have you done any kind of true lubricity testing to compare? Because I’m sure a lot of people on the call are wondering what kind of surface friction they’re going to experience. Everyone’s used to and understands PTFE and its performance. Do you have any data? Excellent. Let’s share.
Cheng Wei
Yes, absolutely. I prepared a little bit of data. The left side actually measured the coefficient of friction of a PTFE liner versus a UHMWPE liner, and this is measured using ball-on-flat sliding wear, ASTM G133. It’s a kind of model system, and from the data, you can see that within the error, they’re very close.
It’s really very close to the coefficient of friction of a PTFE liner. But of course, whether this result from the model system can fully reflect real-world performance, I think that is still a question.
For this reason, we also did some application-related tests, and since we are a material solution provider, we are not a catheter manufacturer, we don’t do this alone. Actually, we rely on collaboration with partners, and thanks to them, they are okay with us sharing the results.
So here on the right side, you also see some data on the upper part. It’s a kind of dilator pull-force measurement. Basically, in this case, friction is measured by pulling a matched dilator through a slightly curved catheter.
Then you measure the force from this catheter construction. In the case of PTFE, you see that the measured force is 0.157, and in the case of UHMWPE, it’s 0.198. Yes, it’s a bit higher, but I would say it’s still within the low-force range. So this is one type of application-specific lubricity measurement.
The other example I put here is stent deployment force, because as we know, the catheter is often also used to deliver a stent. In this case, we measured together with a partner the stent loading force to compare the PTFE liner versus our UHMWPE liner.
As you can see, the data is a little spread, actually, even if you look at the same line, but at least you can draw the conclusion that, friction-performance-wise, the UHMWPE liner in this case is on par with the PTFE liner. And actually, here there’s even one point from the PTFE liner missing, because during that experiment, delamination happened.
So I think, in general, this data is not the final answer for everything, but at least I think it’s promising. It shows that the frictional performance is relatively comparable to PTFE. And of course, we still have to work with the whole industry to explore further data and get more insights on specific applications.
25:45 Selection Criteria, Wall Thickness, and Scratch Resistance
Katie Karmelek
Thank you for that. I do just want to remind the audience, if you have any questions, pop them in the Q&A, and we’ll try to get them answered. So just type them in there, and we’ll keep an eye out and try to get your questions answered in real time.
Building on this, when an engineer is building a decision matrix to evaluate a liner material, what other properties should they be prioritizing beyond the coefficient of friction? Is this creep resistance, scratch hardness, or surface energy? In your view, which of those is most commonly underweighted in these evaluations?
Cheng Wei
This question, I think it’s better to ask the audience. I think they are the catheter design engineers, they know better than I do. But of course I can still share a bit of my thoughts. I think what you mentioned are relevant concerns, like creep resistance, scratch resistance, and dimensional stability, and so on.
I’m afraid in the end it will be a subtle balance depending on the specific application.
In my view, I think there are two properties that deserve attention, because they seem to have a general relevance. One is the bondability to the outer jacket.
Even if a liner has excellent friction and mechanical behavior, poor bondability or adhesion to the outer jacket can lead to obvious failure during application in push or torque. So the integrity of that interface is critical. I think that’s number one.
The second one is fatigue resistance.
Because a liner can experience repeated bending, compression, and torsion as the catheter navigates tortuous anatomy.
So good fatigue durability can ensure that the inner surface stays intact and can also let the shaft maintain its mechanical response throughout the procedure without failure. So these two properties, to me, are important.
Katie Karmelek
We want to know more about wall thicknesses, actually, and this came out of an audience question as well. So how are UHMWPE liners produced, and what are the wall thickness limitations?
Cheng Wei
The wall thickness, actually, we have thin-wall capability. Typically it’s 20 to 50 microns, but you can also go thinner and thicker.
We are not really making this tube via ram extrusion or paste extrusion.
We do this via a kind of thin-sheet wrapping process. The process itself is proprietary, so I cannot go into specific details, but conceptually it’s simple. It’s just wrapping, and essentially it is a kind of special form of compression molding.
Because of this methodology, it actually is free from those typical extrusion-related instabilities. That’s why thin wall, in combination with larger diameter, is possible using this kind of processing technique.
Katie Karmelek
Excellent. Thank you for that. Some other concerns when it comes to PTFE are particulates, right? So thinking about scratch resistance and understanding performance when there’s potential for wear or particulate generation, especially under high-cycle sliding conditions.
Can you speak to any differences between UHMWPE and PTFE in terms of scratch resistance?
Cheng Wei
Yes, maybe I can show these results. Basically, scratch resistance can be measured by the so-called scratch hardness.
So here we did the measurement. You put a diamond tip with a tip radius of 50 microns on the surface, and then under a constant force, you linearly scratch it across the surface, and then you can measure the scratch hardness and also scratch width. As you can see clearly from the data, the scratch hardness of UHMWPE is way above the PTFE liner. And of course, that’s also reflected in the scratch width.
Basically, it’s an indication of how much material you take away. So for the PTFE liner, you do see a higher width, which means a higher material loss.
This is the most important difference between UHMWPE and PTFE, because PTFE is an excellent material, particularly in terms of low friction. UHMWPE follows as the second one. However, UHMWPE has a very special property that is very abrasion-resistant and scratch-resistant. The reason for that, as I briefly touched on earlier, is related to its long-chain structure and its high entanglement density, so the whole thing makes the material very robust.
Because of this, UHMWPE is used in orthopedics as a load-bearing surface for hip and knee prostheses. PTFE cannot be used for that purpose. If you think only from the friction perspective, you might come up with PTFE instead of UHMWPE. However, there the wear difference is so obvious.
Katie Karmelek
That’s impressive, actually. It really outperforms PTFE on the wear side specifically.
31:25 Dielectric Strength and Surface Activation
Katie Karmelek
What about dielectric strength? Do you know how dielectric strength compares for UHMWPE versus PTFE?
Cheng Wei
That’s a good question. I’m not that familiar with dielectric strength, because so far we don’t touch that kind of application. But because both molecules are apolar, I would say they are probably a bit comparable. However, I don’t know all the details.
One thing I can say about the difference is that although PTFE is also apolar, when you come to the C-F bond, that’s highly polar. Even if it’s not an ionic bond, because they cancel out along the chain, as a molecule you don’t have polarity. But UHMWPE is apolar even at the C-H bond, because that bond is also very apolar. That’s the difference between these two molecules.
Katie Karmelek
Thank you. That was another audience question.
I think it’s about time for our next poll. And this one is really to broaden the lens a little bit and understand where the audience interest lies beyond liners. So I am going to kick off poll number two.
And we’d like to understand what other form factors of UHMWPE would be of interest to you beyond liners. Maybe fiber, powder, sheet, rods, or even pre-shaped components.
And Cheng Wei, I didn’t know this material could come in so many different form factors. The only one I’ve ever known of was fiber, because I’ve heard of people using it to reinforce a balloon for high pressure. So I’m just curious, from your perspective, if you’ve seen any of these other form factors being used in MedTech.
Cheng Wei
Oh yes, fiber, as you already mentioned, is very widely used. As you mentioned, for reinforcement in non-compliant balloon applications, that is a relatively new application, I would say. But actually our fiber is widely used in orthopedics as a high-strength suture for soft tissue repair, like rotator cuff repair, and also artificial ligaments. You have the anchor on the bones.
So that has already been widely used for many years because of the high strength and low elongation. It gives very good performance.
Powder is also a starting point. It’s like a raw material. Whatever you make in other shapes, you typically start with powder.
But on the other hand, powder sometimes can also be used, for example, for medical filtration. You can sinter the powder and still create a porous structure, so that is still very useful. And the sheet, I mentioned that when we make the liner, we start from a thin sheet.
A rod is probably also kind of intermediate. If you have a very small rod, it can also be used as a kind of implant, but the big rod typically is a precursor for more complicated shapes. Actually, if you imagine acetabular cups or tibial inserts in orthopedics, people start either with a compression-molded larger sheet or they do ram extrusion to create a rod, and then they further machine those bigger blocks into smaller components.
Other pre-shaped components are also possible.
Katie Karmelek
And interestingly, Cheng Wei, more people picked pre-shaped components than any.
Cheng Wei
Right.
Katie Karmelek
But just barely. It seems like it’s a pretty mixed bag in what people are interested in.
Cheng Wei
Right. I’m also surprised to see that, but it’s good for us to know that. I do encourage those in the audience who appreciate the components to contact us afterwards. We want to understand better what you mean, and if there’s such a need, definitely we’ll try to work to meet that requirement.
Katie Karmelek
Well, before we move on from scratch resistance, we’ve had a bunch of Q&A, so thank you everyone. Keep them coming, we love this. And if we don’t get your question answered during the webinar, we will have time at the end. If we don’t get to it at the end, time permitting, we will answer your question offline separately.
As it relates to scratch resistance, people want to know, is the scratch force increased during the test, or held constant?
Cheng Wei
Beautiful question. I think for this measurement, it stays constant. I don’t know exactly how that would evolve if you repeated this many, many times, but based on material science principles, I would expect that it would not go too wild, because when we measure the coefficient of friction, it’s also a dynamic measurement, a kinetic measurement. There you have to run it multiple times. We don’t really see a trend that the scratch resistance or coefficient of friction increases.
That’s why I would say it will keep stable for quite a long time, but at a certain moment, when damage happens, it might go up a little bit.
Katie Karmelek
Also in the case of scratching, would more or less micro-debris be generated from a UHMWPE liner compared to a PTFE?
Cheng Wei
Compared with PTFE, I would say it’s way better with UHMWPE, because as I mentioned, PTFE has a very low coefficient of friction, we know that, but actually one of the explanations for that, if you talk to academia, is because PTFE can easily form a transfer layer. It’s a thin film.
So that is very good in terms of friction, but on the other hand, that is also coupled with its very high wear. Earlier I mentioned that the chains are slippery, right? That also explains why it’s easy to have debris from a PTFE liner, because it’s just easy to creep and flow because of the easy sliding of the chains. But for UHMWPE, it’s much more difficult because it’s a highly entangled network. That’s why if you want to pull out a chain from the UHMWPE system, it’s way more difficult compared with PTFE.
Katie Karmelek
Thank you for that. Let’s talk about surface activation. We know PTFE needs to be etched in order to bond to it. What considerations are there for UHMWPE?
Cheng Wei
UHMWPE, as I also briefly touched on, is also an apolar molecule. If you’re thinking about the catheter application, it needs to have good bondability with the jacket, typically TPU or Pebax. Those are more polar molecules. So if we don’t do any surface treatment, I would say the only interaction there is a weak kind of force.
It may work for some less demanding applications, but for most applications, I do expect we need to have surface activation as well.
And this can be done via plasma treatment, in contrast to the conventional treatment used with PTFE, because PTFE is typically treated by a chemical agent, using sodium ammonia or naphthalene.
A normal plasma treatment is not very effective for a PTFE surface. It does something there, but it’s not very effective. However, it can be very effective for treating the UHMWPE surface.
As you can see here, I put some pictures. On the left side, we see a contact angle measurement. The upper one is the native UHMWPE liner without any treatment. You get a contact angle around 100 degrees, depending on how you measure it, maybe 110 or 105.
Then after plasma treatment, you can drop that to 50 degrees, and if you really optimize the process, you can even drop it to almost 10 degrees. That is really, really hydrophilic. So that’s very impressive.
And of course, when we also compared the peel force against PTFE together with a partner, by and large I think they are on par, but I would say UHMWPE liners even outperform PTFE in terms of bonding strength.
So the short answer is, you do need activation, but it’s a relatively simple process.
Katie Karmelek
Compared to etching, the plasma activation is a lot easier and simpler in general.
Cheng Wei
I think so. Particularly, there’s one extra advantage. Even for these tubes, after etching, with time it may decay a bit, but you can easily implement an atmospheric inline plasma treatment machine, and before you do the assembly and reflow, you can still have a refreshing process, so that makes sure that your surface is most fresh.
Katie Karmelek
Oh, interesting. That makes a lot of sense. That’s really cool.
40:32 Sterilization, Shelf Life, Regulation, and Sustainability
Katie Karmelek
Let’s switch gears and talk a little bit about sterilization. So, for many OEMs, this is a critical validation gate. If you could just talk to us a little bit about mechanical property retention data that might exist for UHMWPE after gamma or e-beam. Can it be EtO sterilized? Talk to us a little bit about sterilization implications.
Cheng Wei
For EtO, I think everyone knows that nothing will really happen, so that’s relatively safe. And for gamma and e-beam, probably the concern is there. So we did run our material through a typical gamma sterilization process, and what we found is that we did not really observe a statistically meaningful mechanical strength drop after the demonstration. I mean our UHMWPE liner tube. I need to give a warning here.
Which material, in which physical form, you submit to this radiation matters. If you submit our fiber directly to gamma irradiation, then you will see a clear drop. But in this case, for the liner, we did not really see a statistically meaningful drop in mechanical strength. And then we also did a shelf-life accelerated aging test on those gamma-sterilized tubes. Again, we did not really observe a significant drop in mechanical strength.
I think at least such data show that there’s great potential to use high-energy irradiation to sterilize a UHMWPE liner. But ultimately, the verification has to be done by the catheter manufacturer in the real device build and using the real processing window. But our data is encouraging.
Katie Karmelek
Excellent. That really opens the door to other sterilization options that don’t exist for PTFE, so that’s really exciting.
I’m going to circle back to plasma etching, because there seem to be a bunch of questions around that that I want to come back to. A lot of people are saying that plasma typically wears off pretty quickly. What shelf-life considerations are there for the plasma-treated surface? And I know you mentioned adding it inline so you can freshen it, so to speak.
Can you build on that a little bit?
Cheng Wei
Yes. We don’t have complete data, so what we did was some preliminary checks, so this would be indicative. First of all, I think we can make a comparison between the effect after chemical etch on PTFE versus after plasma treatment of UHMWPE.
For PTFE, the chemical etching actually creates a thin and conjugated carbon-rich polar interface on the surface that is chemically sensitive to oxygen, light, and humidity. So the good bondability can drop from a few hours to a few days if left exposed.
The reason is it’s a chemical deactivation process.
For plasma-treated UHMWPE, the surface will have some oxygen-containing functional groups, like hydroxyl, carbonyl, and carboxyl groups, and these groups are relatively stable.
So its deactivation happens via a kind of hydrophobic recovery. It’s a physical and thermodynamically driven process in which the polar groups on the surface can become buried underneath the surface with time, due to local chain rotation and relaxation. And this is a slower process.
So good bondability of a UHMWPE liner after plasma treatment can last for a few days, up to a few weeks, even longer, depending on the conditions.
That said, it does not automatically translate to a practically longer shelf life for a UHMWPE liner, because the chemical deactivation of etched PTFE can be slowed down by proper packaging, using opaque and sealed bags to limit oxygen and light.
But you cannot use packaging to slow down physical aging. So I think in a practical sense, the shelf life of a UHMWPE liner would be a few weeks to a few months, depending on the detailed situation of the material specifics and the plasma conditions.
However, I still tend to believe that if you could have inline plasma treatment, it can always refresh. That would definitely help, and you cannot meaningfully do that with a PTFE liner, because if you do that, I’m not sure whether it will be positive or negative, to be honest.
Katie Karmelek
Oh, that’s helpful.
When we think about more widely adopting this, you mentioned UHMWPE is really heavily involved in orthopedic implants and that space. It’s very well characterized, but the thin-film extrusion context for interventional devices is different. How much of that legacy data do you think is directly transferable from orthopedics into interventional devices?
Cheng Wei
This is a good question. Probably we need to ask a regulatory expert, but from my perspective, there are a few things. First, UHMWPE already has a very good clinical record in orthopedics that we discussed.
And actually, in recent years, it’s also been used in cardiovascular applications, such as, for example, the skirt in the TAVR system.
These two are from orthopedics applications, and this one is a TAVR system, and here it’s a skirt, and this skirt could be made of UHMWPE as well, even though PET is also used, of course.
As far as I know, the FDA has approved catheters and sheaths that use HDPE as a shaft material, not as a liner, but as a shaft material. So that somehow indicates that the FDA is familiar with polyethylene in general.
You’re right, coming to the liner application, we do need to do all the refiling from a regulatory perspective and also full revalidation. However, I think as long as the performance aspect can be demonstrated, the concern from biosafety and biocompatibility is minimal.
And also, from dsm-firmenich, we provide medical-grade UHMWPE, and our quality system follows ISO 13485, so we will fully support our customers during their regulatory submission.
We actually also have an FDA master file, which our customers can reference during their filing. I hope that could really reduce, or at least streamline, their regulatory burden.
Katie Karmelek
Absolutely. Speaking of that, are there any additives in the liner that folks on the line should be concerned about?
Cheng Wei
No, it is pure polyethylene. There’s no additives.
Katie Karmelek
Excellent.
I’m going to just ask one more question, we’ll do one more poll, and then we’re going to get into formal Q&A and answer a whole bunch of other questions. So keep them coming, this is great.
We talked a lot today about regulatory pressure and performance. Looking at DSM Biomedical’s own EcoVadis Platinum rating, placing you in the top 1% of assessed companies globally, I want to ask directly, do you foresee sustainability becoming a formally defined design input in vascular device development over the next, let’s say, five to 10 years? Not just a PR statement, but an actual material selection criterion?
Cheng Wei
Thank you for bringing that up. We are proud that we earned this platinum medal from EcoVadis, because it gave us a position really among the top companies they have assessed in the past 12 months.
In my own view, I think so. In the next five to 10 years, I do expect sustainability to be an explicit design input in vascular devices. Not necessarily as a primary driver, but definitely as a formalized constraint.
Actually, we already see such signals. It’s even beyond PFAS. We already touched on the increasing scrutiny on EtO sterilization emissions, the growing interest in recyclable packaging, and even hospital-level sustainability metrics.
From our own interactions with large device companies, we’ve seen that their procurement teams have already started to put sustainability criteria into their qualification checklists.
And within dsm-firmenich, we have already, for several years, required a sustainability assessment before initiating any new project. So it’s a must. It’s a way of doing things. So I think this shift is already underway. That’s why I expect that in the next five to 10 years, sustainability will become a defined and measurable design input.
50:23 Audience Q&A and Closing Remarks
Katie Karmelek
Thank you for that. I’m going to launch the last poll, I believe. Poll number three, and last poll. Which other applications would you think of in relation to UHMWPE as a replacement for PTFE?
It’s not letting me launch it. I don’t know why. Hopefully you guys can see it and vote on it. If you can’t, maybe we won’t get this feedback, but my launch button is gray. Oh, there we go. Here we go. Let’s see if I can launch it now.
There we go. Now you should be able to answer the question. Which other applications would you think of in relation to UHMWPE as a replacement for PTFE? So, a stent graft, an occlusion device, valve suture, embolization device, or vascular graft.
And this is really fun to get into a little bit more of the application side, right? Going really far upstream with material science to really putting this into a patient and what that really means. And that’s what I think we’re all equally passionate about here.
Excellent. We’ll give folks another minute.
What I really like about these polls today, Cheng Wei, is that it’s been a pretty wide range of answers. We’re not getting everybody answering in one way, which is great. I think it’s really nice to see there are opportunities on the different form factors, opportunities on the different applications. This has been really helpful. So thank you, audience, for participating, because it’s really great to see where your head’s at and how this material might help you.
All right, so let’s see. We’re going to end the poll and share the results, and that looks like 66% of folks really would think of vascular grafts, with the stent graft as kind of the next in line. Interesting.
Good stuff.
We are just about nine more minutes left in the time, so I think that really brings us to the end of the main discussion.
We’ve already had some great questions come in. We’re going to take as many of the remaining questions as we can in the last few minutes here. If you haven’t submitted a question, feel free to do so in Q&A. If you didn’t get an answer today, we will respond directly to you.
A question that actually came up a couple of times, Cheng Wei. People want to know if UHMWPE can be made into a heat-shrinkable material, like PTFE can.
Cheng Wei
In principle, yes. Heat shrink is more related to polymer physics instead of the detailed chemical structure of the material itself, so that’s why we have PTFE shrink tube, or polyester, or even polyolefin. So I think in principle it’s possible, but one needs to consider the economic aspect as well.
Katie Karmelek
Okay, interesting. When we think about making UHMWPE tubing, how big of a tube can be produced? Are we limited on any OD constraints?
Cheng Wei
No, with our method, I would say for cardiovascular application there is no limit. You can go from as small as about half a millimeter to a few centimeters. Even for an aortic type of device, three or four centimeters is possible. Because, as I said, our process is not based on extrusion, so it’s a wrapping process. Therefore it’s not really limited by the diameter.
Katie Karmelek
So this is interesting. When catheter designers are reflowing, they often stretch the PTFE liner. It helps maintain positioning and control the final ID of the product. What happens in the same scenario with UHMWPE when it’s stretched longitudinally?
Cheng Wei
Beautiful question. Actually, my own thinking is that probably for a UHMWPE liner, we can get rid of that step. At least that is what I’m aiming for, because the reason you need to stretch is, first of all, you want easy insertion onto the mandrel, and I think that’s probably the main reason.
In our case, you can still stretch it, it still has some stretchability, but I think that’s probably not the best practice. The best practice is probably that we can make it slightly larger, so that you can still easily insert the tube onto the mandrel, but then you just build up the assembly, and during the reflow process it automatically will grip.
Or even before that, for example, you can also do some thermal treatment and it will grip because of thermal effect.
Why? Because, as I mentioned, UHMWPE has a much lower melting temperature than PTFE, so it’s very easy to achieve a thermal gripping effect as well.
Katie Karmelek
Thank you for that. Can you comment on wall thickness or dimensional preservation during the reflow process? Given that it will be in a molten gel state during reflow, should engineers factor in dimensional changes resulting from reflow in the original liner dimensions?
Cheng Wei
Yes, this is something I think we need to explore together with catheter design engineers. As I mentioned, the starting liner will change during the reflow.
So that means the thickness in the beginning does not necessarily reflect the final thickness after reflow. This is different from a PTFE liner.
However, typically, as you can imagine, during reflow, under pressure and also during melting, it will go down in thickness.
So in other words, if you start maybe with, I’ll just give you an example, 30 microns, maybe you end up in the end with 25 or even 20, depending on the initial state, which to me is not necessarily a bad thing. But how to do that correlation, I think we still need more data to find out together with downstream partners.
Katie Karmelek
It still needs to be characterized further so we can design the proper starting dimensions to get the ultimate end-result dimensions we need. That makes a lot of sense.
So, since UHMWPE has more strength, will this cause issues with catheter flexibility when we’re thinking about highly tortuous anatomy?
Cheng Wei
Not necessarily. I think the total flexibility is not only determined by the liner, but also by the reinforcement element and the jacket. I think it’s a combination. And there is still a chance to make a UHMWPE liner soft.
There’s a way to tune that.
Because when you do the reflow, yes, the reflow melts everything, but on the other hand, you can also think about maybe very low-temperature bonding for some special part or particular segment that may change the whole story. So I think it’s a combination.
But I don’t really see at the beginning that because of the high strength, that automatically translates into poor flexibility. On the other hand, because of the better fatigue resistance, I would say that for some devices like steerable ones, where you have more bending cycles, it might even be beneficial, because it will not really have cold flow or other kinds of easy deformation.
Katie Karmelek
Okay, so we’ve got a couple more. We’re getting into the specifics around reinforced catheter shafts, right? We’ve got braid, we’ve got coil, we’ve got some metals in there. So people are wondering if there’s a risk of the braid or coil seeping into the ID underneath the UHMWPE, and also another similar question is, due to the low melting temperature, when coiling directly onto a lined mandrel, would the coil wire tension have to be reduced to avoid exposing the coil through the ID of the liner?
Cheng Wei
I think that’s a very excellent concern. Based on what we have seen so far, there’s no such big risk. We haven’t seen this happening, but I cannot say there’s no risk at all, so this is still something we need to further zoom in on.
But based on available data, there’s no such kind of scoring or cutting through, because this is thanks to the high melt viscosity and melt strength of UHMWPE. Again, it emphasizes why in this case ultra-high molecular weight is so important.
But this is definitely a very pertinent concern. So far, based on what we have seen, we don’t see any feedback that the coiling or reinforcement is cutting through.
Katie Karmelek
I think we have time for maybe one or two more questions. A couple of folks are interested in understanding how easily the reflowed catheter will release from the support mandrel and the ID when we think about UHMWPE compared to a normal PTFE liner during reflow.
Cheng Wei
This one, I would say, is probably on par, because from our side, as a material provider, we don’t do a lot of catheter builds in-house. That’s why we hear feedback from partners who do that. They say it’s kind of similar to PTFE. Maybe in some cases it can be a little bit worse, but definitely it’s releasable. You can just drag it through after you build up the whole assembly.
Katie Karmelek
Excellent, thank you for that. And is it possible to supply these on a spool, which could then be extruded in an over-the-wire extrusion process?
Cheng Wei
Not at this moment, because, as I mentioned, we don’t do this via an extrusion process, so that’s why it’s not possible to make it on a spool. But we are also further working on that to explore other means to see whether we can achieve that. But at this moment, no.
Katie Karmelek
All right, I’ll answer one more that just came in, and then we’ll wrap this up, because we want to be really mindful of everyone’s time here. PTFE liners can be produced with different mechanical properties due to ram extrusion parameters, but is there such a manufacturing option for UHMWPE?
Cheng Wei
This comes through, I think, a wonderful earlier question on flexibility. I think yes and no. There is some window we can tune, but this highly depends on the final reflow temperature and combination, because the whole reflow process, in a sense, is about bonding the outer jacket with the liner. It’s not necessarily that you have to do a thermal reflow.
So if we are able to tune there, I think there’s a chance to tune the properties there. And of course, the final property will also be determined by the starting material. For example, the exact molecular weight, molecular weight distribution, and those things will also have an impact on the final properties, even if you do the melt reflow.
Katie Karmelek
Thank you.
With that, we’re going to wrap up today’s session. Cheng Wei, thank you so much. This has been a genuinely rigorous look at the data, and I think everyone here has come away with a much clearer picture of where UHMWPE stands as an engineering option. Really appreciate your time and expertise. For everyone on the call, the recording will be in your inbox, hopefully by the end of this week.
If you want to go deeper on the UHMWPE platform, DSM Biomedical is available to take any questions or any follow-on inquiries. But also, please check out our Resource Hub.
It’s right in the navigation of every page on Chamfr, with webinars, technical articles, podcasts, and conference coverage to help you stay ahead in MedTech R&D.
And speaking of conferences, mark your calendars, because we’ve got MPP West, April 8 in Mountain View, California, MPP East is June 24 in Boston, Massachusetts, and more regional events are coming. These are fantastic opportunities to continue exactly this kind of conversation we had today.
And also, we’ve got more webinars coming up. I’m actually hosting the next one, so hopefully you don’t get sick of hearing from me. April 22, we’ll be rethinking your heat shrink, with Barry Schnur and Alex Miranda from Cobalt Polymers, and really diving into Pebax and polyolefin heat shrinks.
So thank you all for joining, thank you again to our sponsors, ICS Medical Devices and LightningCath. Also follow us, subscribe to our emails, find us on LinkedIn, and really just have a great rest of your day. Thank you for being here.
Cheng Wei
Thank you, everyone. Thank you, Katie. Bye-bye.
Katie Karmelek
Thank you, Cheng Wei. Take care.