Finishing and coating providers are in high demand in the medical device industry, especially for electropolishing and passivation services. Although they have plenty of work, there are still some supply chain delays, especially for materials. Surface requirements by medical device manufacturers (MDMs) are getting more complicated, which often require innovative solutions or multiple surface treatments. And, as regulatory standards evolve, MDMs also count on sound regulatory knowledge and guidance from their finishing providers.

For example, “there is long-term uncertainty in the coating industry with the European Chemicals Agency’s regulatory proposal to restrict the manufacturing, sale, and use of PFAS [per- and polyfluoroalkyl substances] in the EU,” said Kyle Hedges, product manager for Applied Plastics, a Norwood, Mass.-based provider of coating services for the medical device industry. “With the final proposal in review, this uncertainty has forced MDMs, contract manufacturers, and suppliers to look more deeply into their supply chain for alternatives and consistent product supply.”

These regulatory and supply chain issues are also compelling MDMs to see what other processing services their contract manufacturers (CMs) might be able to provide. “MDMs are searching for the best long-term coating partner that can provide reliable inventory and resources while adapting to the ever-changing environment and their product development needs,” continued Hedges.

For these reasons, as well as the ongoing consolidation within the finishing industry, MDMs are expanding their search for qualified finishing sources to reduce delays and improve time to market.

“We are seeing new opportunities and new customer inquiries from many different parts of the country,” said Luke Almeida, COO for New England Electropolishing, a Fall River, Mass.-based provider of electropolishing and passivation services for stainless steel components. “The ability to communicate and discuss projects remotely via Zoom has made communications more seamless and streamlined.”

In the orthopedic market, the most popular coatings are those for cementless joint reconstruction implants. “The goal is to enable direct fixation between the artificial component and the hosting tissues,” said Pierfrancesco Robotti, technology and business development manager for Lincotek Medical, a Trento, Italy-based provider of thermal plasma spray and other surface treatments for the medical device industry. “We use thermal plasma spray coatings and additive manufacturing to deliver porous surfaces in biocompatible metals that promote direct bone on-growth and in-growth for long-term stable fixation.”

Surface coatings have also become standard for vascular and non-vascular medical device applications that seek to improve trackability, hemocompatibility, and therapeutic benefits such as drug delivery. “These coatings are especially favored in the coronary, peripheral, neuro, and structural heart segments,” said Charlie Olson, senior vice president and president, medical device coatings for Surmodics Coatings, an Eden Prairie, Minn.-based provider of advanced hydrophilic, hemocompatible, and site-specific drug-delivery coating technologies.

Current Trends

Some of the more popular coatings for medical devices are those that enhance wear performance on articulating surfaces. Ceramic coatings such as titanium-nickel, titanium-niobium-nickel, and zirconium-nickel are often used for these applications and also reduce the release of metal ions, which can be a serious health problem for people sensitive to certain materials such as cobalt and chromium. Titanium anodizing is another popular surface treatment that improves implant performance and/or size identification through color coding.

Porous lattice structures for implants continue to evolve, creating greater interconnected porosity with larger-sized pores. Calcium phosphate-based coatings, manufactured through electrochemical or chemical processes, “are a perfect match for these porous structures,” said Robotti. “In fact, the few microns of thickness do not interfere with pore interconnection and can easily penetrate inside complex shapes, or reach out-of-line-of-sight surfaces. Electrochemical thin calcium phosphate coatings [brushite, for example] and NanoHa chemical deposition are gaining in popularity because they are more easily coupled with porous coatings to accelerate bone colonization inside the lattice structures.”

Another material property of keen interest to MDMs is lubricity, especially for catheters and devices that must navigate challenging parts of the anatomy. The goal is to maximize lubricity without sacrificing durability or increasing particulates. Although novel softer substrates can enhance the deliverability of a catheter, coating solutions must be compatible with these newer materials.

“Advanced access systems are designed to reach the most distal regions of the vasculature and/or cross complex, difficult lesions and reduce procedural times,” said Olson. “High-performance coatings can help achieve many of these objectives. Next-generation surface technologies must also successfully meet evolving and rigorous regulatory guidelines and increased coating characterization requirements.”

There is strong interest among MDMs for matte finishes. Surgeons are often concerned about reflectivity in the operating room. Because many implant parts and components are made from stainless steel, which can create glare, MDMs are asking for matte, non-reflective finishes. To meet this need, New England Electropolishing has developed ElectroMatte, a proprietary electropolishing process that produces a non-reflective finish on stainless steel components. “It serves as an alternative to chemical cleaning or pickling procedures, which are more difficult to control and less environmentally friendly,” said Almeida. This multi-step procedure cleans, deburrs, and passivates metal and stainless steel parts and components while producing a non-reflective finish.

What MDMs Want

Quality requirements continue to be at the forefront of vendor selection and qualification. “Quality and project engineers want to know that your processes have been validated [installation qualification/operational qualification/performance qualification] and that prospective suppliers have process failure mode and effects analysis [PFMEA] in place for processing lines and equipment used in medical device finishing,” said Almeida. “Simply having an ISO certification is no longer enough to satisfy prospective customers.”

MDMs want reliable partners with proven quality systems and manufacturing processes that allow them to focus on their end product’s innovative therapy while being confident their coating requirements are managed by experts. “MDMs also want to move product development revisions quickly, meaning available materials are being leveraged in R&D labs,” said Hedges. “Our Applied Plastics Online Store is readily available so engineers can shop online and order in-stock materials to ship the same day. We consistently monitor customer demand and market trends to ensure that we provide our customers with the products they need to ensure projects remain on schedule.”

Vertical integration (more services per vendor) is another way of speeding up product development and building shorter, more reliable supply chains. These vendors can provide multiple finish requirements in a single step, saving time and money. “We have positioned our electropolishing to be a ‘one-stop-shop’ for micro-deburring, microfinish improvement, pathogen resistance, cleanliness, and passivation—all in one operation,” said Scott Potter, vice president of sales for Able Electropolishing, a Chicago, Ill.-based provider of electropolishing and nitric and citric passivation services for the medical device industry.

For materials, MDMs want durable surface treatments that enhance the biocompatibility of their medical devices. This is especially critical for implants and devices subjected to mechanical stress during use. MDMs continue to rely on electropolishing for surface roughness reduction, which is important for biocompatibility and minimizing friction.

Another must for MDMs is “having the capability to scale up to follow mass production, with the shortest possible delivery time,” said Robotti. “Quantity to be treated is often important, so inventory cost can quickly become an issue. The reverse is also true—being able to adapt production to small-size batches.”

Advanced Tools and Technologies

Additive manufacturing (AM) techniques are increasingly used to create smaller, customized medical devices, with more complex geometries. For example, AM can deliver tailored porous lattices at exact locations within the device, with specific thicknesses and pore sizes. “As an example,” said Robotti, “we have manufactured devices for orthopedic oncology that contain, within the same component, different types of porous lattices and surface finishing to interface with expected different tissues, such as soft tissue, ligaments, cancellous bone, and cortical bone. This was not possible to do with a homogeneous conventional porous coating.”

Although the surface finishes for AM-manufactured parts have improved, they are still not as good as finishes produced with traditional machining. In most cases, the 3D-printed finish is still too rough to go directly from AM to electropolishing, as with a traditionally machined part. “Electropolishing is most effective in a range of 32 Ra to 4 Ra and can improve the finish of AM-made parts,” said Potter. “Electropolishing is best when used with a 32 Ra or better starting finish. We get customers looking to take a part that has a 125 Ra finish down to a 16 Ra, for example, but we can only improve that finish by 50%.”

Another issue with AM is metal powder evacuation from lattice structures created through the AM process. Lincotek Medical has developed a special type of cleaning process (iXClean) that ensures maximum cleanness/safety to the surface while preserving production efficiency and suitable delivery time. “We have also developed an inline quality control [LInside] process that detects internal defects in the solid sections of AM devices,” said Robotti. “The technology makes use of machine learning, so several batches are needed for training the system, which is proving to be robust and scalable. Before, these types of quality controls were high cost and/or required destruction of the part, and thus, were limited to validation batches only.”

Nanotechnology has enabled special coatings with nanometric features. “For example, NanoHA, a cold chemical deposition process, can be used to coat polymeric substrate and insulator materials that otherwise could not accept other coating methods originally developed for metal substrates,” added Robotti.

Nanotexturing of a component or device can improve bone tissue adhesion on the implant surface. Titanium micro and nanotexturing are alternative strategies for MDMs that prefer not to use calcium phosphates. Laser surface texturing can provide micro- and nano-texture patterns for a broad variety of biomaterials, creating a surface roughness ranging from macro-roughness [Ra scale around 10µm] to nano-roughness [Ra scale <200 nm]. Nanoparticle-based coatings (typically silver) have been developed to discourage bacteria adhesion on the surfaces of implantable devices.

In February 2024, EVOQ Nano, an Ogden, Utah-based nanoscience company, announced its new antimicrobial medical device platform that is highly effective in fighting hospital-associated infections.¹ By infusing its proprietary nanoparticle—EVQ-218—throughout the polymer that makes up the device, the process provides a constant antimicrobial surface that eliminates the need for coatings, which wear out over time.

Another high-precision technology ideal for selectively targeting surface areas on small, intricate, and delicate parts is microblasting. Very fine abrasives (17.5-350 µ) and very small nozzles (0.018-0.125 inches) are used together to provide the pinpoint precision needed to remove coatings more safely and efficiently compared to mechanical, thermal, or chemical methods.

“Regardless of the type of coating, two opposing issues bring Comco into discussions,” said Colin Weightman, director of technology for Comco, a Burbank, Calif.-based manufacturer of micro-precision sandblasting equipment. “The first is how to get the coating to properly adhere to the base material. The second issue then becomes how to selectively remove sections of the coating once it has been applied to the base material.”

The first step is blasting before the coating is applied. An aggressive abrasive media is used to engineer specific surface features ideally suited to improve the bond between the coating and the base material. In addition to specifying Ra, microblasting can also be measured through pore size and developed surface. The process works equally well on thin polymer layers as well as hard ceramic or metal materials. “Abrasive selection, nozzle selection, blast time, and blast pressure are determined by the coating properties,” said Weightman. “These variables are dialed in during a sample test or by a process engineer. Once the blasting recipe is set, keeping results constant is relatively easy.”

Step two is blasting to remove any excess coating. By simply changing the abrasive and blast parameters, microblasting can remove coating with high accuracy. “An abrasive with a blocky-shaped particle may quickly and easily remove one type of coating but smear another type,” said Weightman. “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.”

Regulatory Demands

To meet regulatory standards, MDMs look for surface treatments and coatings that comply with relevant regulations and standards, ensuring the safety and efficacy of their medical devices. In addition, companies seek surface treatments that can withstand common sterilization methods without compromising the properties or functionality of their devices. For example, MDMs utilize anodic surface treatments for their reusable surgical instruments, cases, and trays, which can hopefully withstand the cleaning processes that are typically caustic, with high pH; these conditions, however, can dissolve conventional Type II and Type III anodizing after multiple cycles. “Precision Coating’s patented MICRALOX anodic coating solution, which provides superior corrosion resistance, can withstand these harsh environments,” said Jordan Gaulin, NPI engineering manager for Precision Coating Company, a Hudson, Mass.-based provider of hydrophobic coatings, anodic coatings, ion implantation, and laser nanotexturing for the medical device industry. “Our engineering team has the experience to offer critical design for manufacturability with creative processing solutions to satisfy most complex coating challenges.”

MDMs also want to use materials and finishes with minimal environmental and human health impacts and those produced using sustainable practices. There is a current trend toward switching to functional coatings that meet or exceed all regulatory requirements and are free of perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), hexavalent chrome, and harsh solvents.

Legislation for PFAS compounds is pending in the EU and the U.S. There will likely be a derogation, or waiver, for medical devices and other critical-use applications where there are no currently available alternatives. “For us to provide long-term material options, we must be prepared for a future that may be transitioning away from PFAS-containing coatings,” said, Michael Drahiem, process engineer for Precision Coating Company. “This future may take many forms and we have multiple paths we are preparing for. One major initiative Precision Coating is working on is our EcoGlide coating, which is PFAS-free, NMP [N-Methylpyrrolidone]-free, and chromic acid-free. We are well into chemistry development with promising results thus far.”

Due to the ever-changing regulatory environment governing the use of polytetrafluoroethylene (PTFE), some suppliers have also decided to stop producing their lines of fluoropolymers. “Applied Plastics continues to monitor the regulatory environment and works to diversify our material suppliers to minimize any disruptions caused by regulatory changes or end-of-life announcements,” said Hedges.

Surmodics has a 35-plus-year history of supporting customers’ regulatory filings. “We have a robust, proven toolbox of coating characterization methods,” said Olson. “These include simulated use models based on complex clinically relevant models and testing around lubricity, durability, coating integrity, and particulate. The tests address many of the questions typically posed by regulators.”

In fact, the company has fostered an interactive, collaborative approach with regulatory authorities to facilitate a deeper understanding of the key considerations for adopting a coating. Participation in the FDA CDRH’s Experiential Learning Program has allowed Surmodics to share its coating knowledge with review staff through on-site visits, demonstrations, and interactive discussions. “We also gain a better understanding of regulators’ key issues so we can offer the most value to our customers regarding what regulators want and need to know,” said Olson.

Next-Generation Innovation

MDMs and their CMs are continually investing in and developing next-generation surface modification technologies, including single-coat formulations with rapid manufacturing cycle times that meet stringent requirements for lubricity and durability. Scientists are also looking at ways to combine, in a single process, important coating properties such as wear resistance, osseointegration, and resistance to bacterial infection. “This will help to simplify the manufacturing and the supply chain, negating the need for several separate coatings/surface treatments, which is the current state of the art,” said Robotti. “This will also reduce cost and delivery time, with improved performance.”

The use of Internet of Things (IoT) technologies such as artificial intelligence and machine learning, combined with advanced manufacturing methods, will accelerate the development of new coating and finishing processes. These methods will become more mainstream and accessible to finishers, allowing them to be more competitive and efficient, speeding up production times, and increasing quality and processing predictability.

The most popular IoT technology in the medical device industry is automation. For Potter, the use of automation and robotics “provides better consistency from rack to rack and lot to lot and allows us to turn larger volume orders around in a fraction of the time compared to manual systems.”

MDMs are already adapting to robotic manufacturing and will continue to press their suppliers to become automated. Additionally, in the near future, finishers will be selected to be part of an MDM’s supply chain based on whether they have automated processes that enable faster development cycles.

As technologies advance, MDMs will become more confident with new materials, technologies, and designs. They will be emboldened to design more unique devices for a wider range of applications than in the past. Customers continue to request unusual shapes and applications for their new products—as a result, coatings requirements are becoming more diverse. For example, “we have received increased requests for complex custom ground mandrel configurations,” said Hedges. “These increasingly complex designs can be challenging to coat. We engage with the customer to understand the application and ensure our solution meets their requirements.”

“Ultimately, to support rapidly evolving device requirements and to be a valued technology partner, surface modification providers must offer a complete, fully characterized array of technologies, capabilities, and processes, coupled with experienced engineering applications resources, to quickly support new and novel interventional applications—from the earliest product development phase all the way through the device lifecycle,” said Olson. 

Reference

1. tinyurl.com/yd2mtj2j

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Mark Crawford is a full-time freelance business and marketing/communications writer based in Corrales, N.M. His clients range from startups to global manufacturing leaders. He has written for MPO and ODT magazines for more than 15 years and is the author of five books.