Discovering the Value of Surface Treatments and Coatings for Medtech
Medical device manufacturers (MDMs) have long been interested in improving the performance of their medical device substrates through the use of engineered coatings, especially as components become smaller and more complex, with enhanced functionality. As the number of elective diagnostic and surgical procedures approach pre-COVID-19 levels, MDMs are again eager to utilize both standard and specialized coatings and application technologies to increase the functionality, performance, and lifespan of their medical devices.
Surface treatments in the medical device industry are showing substantial growth through innovation—especially in the electrosurgery and minimally invasive surgery fields, which typically require specialized surface properties for easy insertion, navigation, and trackability. In fact, unique surface coatings and treatments are generating as much excitement in the medical industry as new devices because they are broadening medical design options for engineers.
With surgeries on the rise, and innovation and R&D at the forefront, perhaps the only major point of concern is that supply chains still suffer from continued disruptions—in fact, for many MDMs, delays and shortages are worse now than they were at the height of the pandemic.
“It began on the demand side with the lockdowns, which necessarily curtailed elective surgeries,” said Dana Barnard, CEO of Himed, an Old Bethpage, N.Y.-based provider of surface treatments for dental and orthopedic implants. “Business restrictions—including travel bans—limited communication and collaboration, which has made routine forecasting and forward planning challenging for everyone. Now the supply chain is getting disrupted again from the material supply side. The industry is seeing critical materials shortages, rapid and sometimes remarkable price increases, and in many countries, labor shortages.”
For these reasons, many MDMs are re-evaluating their supply chains and suppliers to better determine their abilities to safely and predictably deliver products and materials, as well as manage their own vendors (fourth-party suppliers to MDMs). With many coatings and constituent ingredients coming from other countries, MDMs are looking to diversify risk by adding backup suppliers or shortening their supply chains to be less vulnerable to supply chain shocks (and, in turn, be more agile in response).
Acquisitions in the medical device coating industry are increasing rapidly, supporting the growing demand for coatings in the medical industry. Several coating companies and venture-capital firms made mergers and acquisitions a big part of their activities last year. “The amount of capital to be infused into the industry is about to accelerate innovation beyond what we have seen in the last decade,” said James Morris, president and CEO of Surgical Coatings, a Sedalia, Colo.-based provider of surface coating services for the medical device industry. “It is a fascinating time for the medical device coating industry.”
Advances in surface treatments and coatings are focused on enhancing medical device performance through improved functionality and ease of use, such as improved lubricity and antimicrobial properties.
“Surface modification technologies can improve material properties without negatively impacting the intended function of medical devices,” said Jamie Swenor, business development manager for Evonik Health Care, a solutions provider for the medical device industry. “Useful properties like biocompatibility, lubricity, and antifouling can be enhanced to improve safety and clinical efficacy.”
Bulk device properties, such as flexibility and tensile strength, must be maintained to ensure proper mechanical function and prevent device failure. Current solutions include coatings, surface treatments such as chemical vapor deposition (CVD), impregnations, nano/micro textures, and the use of surface-modifying additives. Properties enabled through surface modification technologies include conductive, antimicrobial, antithrombotic, anti-inflammatory, anti-adhesive, and cell attachment.
Device designers seek surface modification technologies that can achieve multiple performance and safety specifications, but are also easy to implement operationally while complying with quality and regulatory requirements—such as hemocompatible coatings that improve the safety of cardiac surgery equipment or coatings that enhance the lubricity of a catheter surface. Lubricious polytetrafluoroethylene (PTFE), such as Applied Plastics’ PTFE Natural, is in high demand in the manufacturing of complex medical devices. These coated products can be used in a variety of ways, from “reflow or forming mandrels used as manufacturing aids in complex structural heart or electrophysiology catheters to coated core or pull wires used as components in other interventional catheter applications,” said Tom Barrett, CEO for Applied Plastics, a Norwood, Mass.-based manufacturer of coated components for the advanced catheter industry. “PTFE Natural is also ideal for applications that require superior heat or abrasion resistance.”
Automation continues to gain traction as a way to generate consistent quality. “Our customers require precise outcomes, and by having control over the operating conditions, we ensure a repeatable process every time,” said Alison Coye, marketing manager for Precision Coating, a Hudson, Mass.-based provider of coating technologies for medical wire, devices, implants, and instruments. “We coat approximately 89 percent of our product via robotic automation in our fluoropolymer division. Robotic spray arms are programmed for exact tolerances and dispersion control, leading to exceptional performance.”
Morris agreed that automation is vastly improving the quality of coating and surface treatments for medical devices in the production and manufacturing environment. “Manual coating operations in the medical device coating industry will likely be end-of-life by the end of 2022,” he said. “The precision and accuracy of surface coating solutions using automation are extraordinary.”
Durable, highly insulative coatings are also essential for the flawless, long-term performance of surgical robots. There is increased demand for thin, electrically insulative coating solutions that are robust enough to meet the rigorous demands of surgical robotics and endoscopic applications. Although reflectivity and abrasion resistance are also essential, the dielectric strength of a coating candidate for these applications is paramount. “Coatings that can withstand 2kV at less than 0.003 inches in thickness have been challenging to address,” said Morris. “We discovered a way to achieve this by using a hybrid polyurethane material. The effects of pigment packages at this thickness have a significant impact on the underlying dielectric strength. Modifying the pigment package allows us to determine the exact insulative properties that were needed.”
Overall, the industry is recognizing that advanced surface chemistries can create unique properties that go beyond the basics for coatings and treatments. These surfaces have engineered properties that expand functionality and broaden design options for devices. One of these desirable properties is softness. When working with the softer materials, there is a greater chance of solvent or temperature processing damage, which requires specialized processes and formulations to support these projects.
“We are seeing an influx of requests dealing with devices—in many cases multi-modal—that are built smaller with softer materials,” said Robert Hergenrother, vice president of research, development, and innovation for Biocoat, a Horsham, Pa.-based provider of custom-engineered biomaterial coatings for medical devices. “We are also seeing greater interest in inner diameter [ID] coatings, which allow for softer substrate materials or for the insertion of materials that are difficult to push through the vasculature to be included in the device design. ID coatings are typically thermal-cured and Biocoat’s HYDAK coatings are a good match for this application.”
OEMs are highly motivated to find reliable partners with proven quality systems and manufacturing processes in place, which allows them to focus on product development with the confidence that their coating requirements will be well-managed. They also want shorter product development cycles, which is why there is growing emphasis on design for manufacturability studies. And, with the ongoing uncertainties in the supply chain, OEMs want their supply chain partners to be extremely vigilant in managing their own vendors.
“The average life of a medical device is seven to 10 years and OEMs are asking more for proof that substantial process controls and quality management systems are in place to mitigate the risk of building a medical device,” said Morris. “With COVID-19, OEMs are looking to ensure timely continuity throughout their entire supply chains, from the lowest-level vendors to the patient. When supply chains fail, people die.”
Of course, OEMs want to improve patient outcomes but they also want to save money in doing so, which is why many companies are asking for low-particulate surface modifications and coating alternatives to simplify the manufacturing process and save on costs. Since coatings are typically one of the last steps in the development process, engineers look for high-performing, low-particulate coatings that can be easily applied to a medical device. OEMs are also interested in anti-inflammatory surface modifications or materials to prevent encapsulation of long-term implants like biosensors, brain-computer interfaces, and regenerative cell therapies. Surface modifications must also be able to withstand ethylene oxide, gamma, and other sterilization methods.
OEMs want more proof of process control, data collection, and automation for their needs as well as for regulatory compliance. As statistical process controls and data collection (Internet of Things, for example) continue to evolve in the medical device space, more MDMs realize that qualitative tests for abrasion resistance, adhesion, and dielectric strength are inconsistent, noted Morris. “I have to explain to design engineers several times a year that dielectric strength is not a linear relationship and the data listed on a coatings technical data sheet is uncertain at best. The medical device coating industry needs to develop unique testing protocols and standards to give design engineers the data and tools they need to bypass the iterative design process that currently drives coating and surface treatment selection. Nanoindentation is already providing medical device engineers with mechanical properties more desirable than the soon-to-be-obsolete pencil test.”
New Technologies and Tools
Surgical Coating’s Virtual Masking technology is constantly improving. Advancements in field programmable gate array chips, vision systems, and telecentric measurement systems are extending the boundaries for coating applications. Automation systems provide closed-loop control. “We can provide very accurate and unique coating geometries for medical devices by integrating all of these technologies,” said Morris. “An added benefit of these systems is the ability to run post-coating operations in a lights-out environment, which we are actively developing right now. Advancements in image acquisition and telecentric measurement devices help automate our in-process and final inspection while closing the loop on process controls.”
For some projects, removing coating materials is just as important as applying them. Sometimes it is tricky to properly adhere a coating to the base material. Since it is often easier to coat an entire surface than just separate sections, MDMs prefer to coat the entire surface and then selectively remove sections of the coating where needed. This can be achieved through microblasting, which has become a highly accurate and cost-effective process.
Microblasting is a precise and controllable process that expertly removes coatings. The micro-scale of the technology is ideal for selectively targeting surface areas on small, intricate, and delicate parts. Microblasting uses very fine abrasives (17.5-350 µ) and very small nozzles (0.018-0.125 inches). “Together, these tools provide the pinpoint precision needed to remove coatings more safely and efficiently than mechanical, thermal, or chemical methods,” said Colin Weightman, director of technology for Comco, a Burbank, Calif.-based manufacturer of micro-precision sandblasting equipment.
Coating properties define the parameters of the blasting process used. Properties such as material composition, coating thickness, and location on the part help determine abrasive selection, nozzle selection, blast time, and blast pressure. “These variables are dialed in during a sample test or by a process engineer,” said Weightman. “Once the blasting recipe is set, keeping results constant is relatively easy.”
The most important variable in the blasting process is abrasive selection. The size, shape, and hardness of an individual abrasive particle give each media unique characteristics; therefore, every coating must be matched with the right abrasive. “For example,” said Weightman, “an abrasive with a blocky-shaped particle may quickly and easily remove one type of coating but smear another type. One coating may respond well to a sharper particle, while another coating may be too thin for an aggressive media. A good rule of thumb is to start sample testing with one of the softest abrasives, like wheat starch, and work up.”
Unlike conventional sandblasting, microblasting provides far greater control over the blast variables so that transition zones of 0.007 inches or less can be achieved. In addition, no masking is necessary to achieve a sharp delineation between the blasted and unblasted surface.
As the use of advanced adhesives continues to proliferate in medical device manufacturing, a key challenge is providing a durable non-stick solution for assembly fixtures and related tooling. Removal of the excess adhesive on production tooling is critical to ensure repeatability in the manufacturing process. MDMs have struggled to find surface treatments with a blend of lubricity and durability, allowing for optimized performance. Over the past two years, Pioneer Metal Finishing, a Green Bay, Wis.-based provider of surface engineering/treatments for medical devices, has refined three product families for durable, dry lubricity for applications on ferrous and nonferrous substrates.
“NiTuff is a proprietary aluminum anodizing process with low coefficient-of-friction values with very high levels of wear performance,” said Corey Strege, chief commercial officer for Pioneer Metal Finishing. “It is an ideal solution for aluminum tooling or components when anodizing is the preferred surface treatment.” In addition, Pioneer’s NorLube electroless nickel process can be applied to a variety of substrates (including ferrous) and its ChroLube features a mirror functional chrome surface designed to withstand harsh applications in which wear resistance and environmental resistance are important.
Innovation in Action
Surgical Coatings is currently working on developing a retroreflective surface coating for a medical device OEM. Retroreflective coatings are used in surgical navigation procedures and are the next major advancement for retroreflective surfaces. The coatings provide a consistent retroreflective surface, which allows higher precision and accuracy of the navigation technology. “Few medical devices use this technology and there have only been a couple of players in the field over the last 20 years,” said Morris. “Now that some of the IP is public, we are trying to create a more consistent surface and reduce manufacturing costs.”
Evonik Health Care’s Endexo additive chemistries can be used to achieve various surface properties, such as increased hydrophobicity or hydrophilicity. The ability to introduce the surface modification during standard polymer processing steps such as compounding, extrusion, or fiber spinning, and to simultaneously and uniformly modify all surfaces, including the inner lumens and outer surface of catheter tubing, represents a unique advantage. This platform provides flexibility and reduces costs compared to traditional coating technologies.
“We are continuing to develop Endexo additives, which can be blended into polymeric materials used in medical devices to create surfaces with reduced friction, without requiring additional post-manufacturing steps,” said Swenor. The integral nature of an additive-based surface modification technique results in a durable surface effect during use and under flow. “Endexo can provide multi-functional properties such as reduced friction, reduced thrombus, or reduced fouling, offering several clinical benefits within the same surface modification,“ he added.
As customers move toward softer and more flexible materials, Biocoat recommends inner diameter (ID) coatings, which allow the device to reach further into the vasculature through the use of softer materials not limited by the properties of PTFE (for example, stiffness, overall adhesiveness of the PTFE liner, and lumen size of the ID). The newest version of HYDAK thermal coatings enables coating the ID, thereby improving device performance. “More customers are also asking for multidurometer catheter constructs,” said Hergenrother. “These projects can be challenging because the coating needs to adhere to the different substrate materials used in the length of the device. For these unique projects, we offer coatings that can handle from very hard materials, such as nylon, to very soft, such as 52A polyurethanes or silicone rubbers.”
Applied Plastics often receives requests from MDMs that want to utilize different substrate alloys. Uncoated surface finish preparation needs vary based on the alloy being coated. “Our engineering team will identify the best surface preparation for the product,” said Barrett. “For example, various nitinol and stainless steels will require different proprietary preparation processes to ensure adhesion and proper coating.”
Precision Coating utilizes its MICRALOX family of products, which offers aluminum oxide coatings with a microcrystalline barrier. Aluminum anodization has been widely accepted for reusable and non-invasive medical products, such as surgical instruments and trays. Because they experience frequent cleaning and sterilization, they must be able to withstand vigorous performance thresholds. “MICRALOX has revolutionized aluminum anodizing by producing long life cycles, exceptional corrosion resistance, and permanent high-resolution marking and printing capabilities,” said Coye. “It is also the first patented IP for new anodizing technology of commercial importance in more than 25 years.”
As devices get smaller and more complex, coating providers must stay ahead of the technology curve and integrate new technologies and materials into their processes to meet ever-evolving OEM demands or regulatory issues. Innovation is happening at several forefronts. For example, companies are adopting 3D printing in several ways, from the supply of bioactive printing materials to the much-needed post-fabrication surface treatment of 3D-printed polymer or titanium parts. Biocoat continues to work on expanding the full potential of inner diameter coatings. “We believe that ID coatings are a potential match for softer substrate materials and allow for increased penetration into the vasculature that was never before achievable,” said Hergenrother.
The repeated sterilization of reusable metallic medical devices continues to be a challenge due to the advances in sterilization technologies and regulatory requirements. For example, the expanding use of vaporized hydrogen peroxide (VHP) sterilization can cause issues for some types of devices. Aluminum sterilization trays and instrumentation may see significant color fading and surface degradation throughout multiple VHP sterilization cycles. To solve this problem, Pioneer Metal Finishing continues to invest extensively in aluminum anodizing innovation designed to withstand the rigors of the ever-changing sterilization requirements. This year the company will launch its Steri-Safe anodizing platform with a focus on providing a surface treatment with optimized resilience for both autoclave and VHP sterilization throughout the useful life of the device or component.
Surface treatments and coatings have always been a key part of innovation in the medical device industry and will continue to be so in the future. And it is not all fireworks—innovation can be subtle, even if it delivers out-of-the-park results.
Although innovation can sometimes be disruptive, “it is more often the result of many smaller changes, which can still provide significant improvements,” said Barnard. “Regarding surface finish innovation, especially in this era of supply chain challenges, partner with a well-established supplier with a track record of innovation and allow enough time to work through the process, which is always iterative.”