Mark Crawford, Contributing Writer10.14.15
Medical device complexity is advancing at a rapid pace. Medtech OEMs are coming up with more challenging designs and materials to be able to deliver an ever-increasing level of functionality and performance. This is, in part, due to demand for minimally invasive procedures, which require increasingly smaller devices, made from micro-components, parts and tubing. For tubing, this means smaller diameters, thinner walls and more complex lumens to meet today’s clinical requirements. For example, surgeons want thinner catheters that also are easier to insert and manipulate without kinking. Advancements in micro-extrusion allow for the creation of thin-wall, multi-lumen, and striped tubing configurations for complex tubing applications.
With these technological and design goals in mind, OEMs more often count on their tubing vendors to turn their dreams into reality—to add features, reduce product size and reduce cost.
“Tubing is expected to fulfill more functions,” said Lars Gerding, director of technology for Freudenberg Medical, a Carpinteria, Calif.-based global manufacturer of precision molded components and tubing. “There is increased demand for more lumens with nonsymmetric cross sections, an increase in functionality with surface modification, or the incorporation of active additives, such as drugs or antimicrobial agents.”
Robert Donohue, general manager for Natvar, a Tekni-Plex company headquartered in Clayton, N.C., that provides medical tubing and profiles for medical device manufacturers, expects the trend toward minimally invasive surgical device development (including unique fluid-path delivery systems) to continue to accelerate.
“We are increasingly being asked to help our customers design products for delivering highly engineered medications for deposable medical devices that require precise dosing levels, or specific environmental protection against moisture, light, heat or oxygen,” said Donohue.
Another reason for increased miniaturization is the growing trend toward medical device connectivity, where data is transferred from the medical device/patient to an analytical or diagnostic system. This capability allows for the prognostic and strategic medical care of patients, with the benefit of immediate treatment and/or prevention of critical health issues. For example, intracranial brain pressure catheters often consist of a single lumen implant-grade polyurethane catheter protecting the wiring leading to a microchip embedded in a stainless steel tip at the distal end of the catheter. This microchip measures brain pressure, oxygen levels and temperature levels inside the brain of severely injured trauma patients.
“The increasingly advanced neurological and neurovascular devices coming into the market show how thermoplastic polymers, metals and electronics are combined into one product,” said Rudi Gall, managing director for Raumedic, a Leesburg, Va.-based provider of extrusion/tubing, molding, and assembly services to the medical device industry. “Metal wires or cables can be embedded inside tubing walls or are run inside the inner lumen of the tubing to allow for electronic data transfer and transmission from the medical device/patient.”
Top Quality, Tight Tolerances
OEMs have high expectations when it comes to quality and tight tolerances. For example, tubing can get as small as 0.1 millimeters (mm)— 0.004 inch—interior diameter (ID) with a tolerance of 0.0005 inches—a fraction of the size of a human hair. Coil-reinforced catheter sizes can be as small as 1 Fr. Tolerances can be equally impressive for larger catheter shafts. For example, Teleflex Medical OEM, a Gurnee, Ill.-based global provider of custom-engineered medical components, including tubing, catheters and balloons, can make a large-diameter (35 Fr), lined, reinforced catheter shaft with a wall thickness as thin as 0.008 inches with ID tolerance at +/-.002 inches and outer-diameter (OD) tolerance at +/-.002 inches. For an fluorinated ethylene propylene/ethylene tetrafluoroethylene-lined, large-diameter, braided shaft, wall thicknesses can be as thin as 12 Fr (.0055 inches).
Medical device manufacturers also count on the raw-material expertise of their vendors to deliver the materials they need to meet the performance specifications of their products. Requirements range from simple, cost-driven ID/OD high runner to precision cut-to-length tubing with complex cross sections and value-added steps, like skiving, hole punching and drilling.
“Depending on the final application, more customers are also seeking highly sophisticated sub-assemblies, plus connectors or tip forming,” said Gerding.
OEMs also want their suppliers to have control over variability and assure the lot-to-lot consistency of their tubing so the overall device assembly process remains robust. This requires the availability of statistical process data and a closed-loop controlled extrusion process, which can be achieved through in-line measurement systems such as laser microscopes measuring the outer diameter of a tubing and ultrasound to measure the wall thickness.
“Having a stable quality system in place, understanding the market requirements of the medical device and technology market and providing other value-added capabilities is essential for any tubing vendor to become a trusted partner,” said Gall.
Tight tolerances also are essential to verification and validation, helping to create a smoother path to regulatory compliance. This especially is true for more complex products, including miniaturized devices and combination products. Achievements made in extrusion lines and related auxiliary equipment allow better process control with in-line inspections, resulting in consistent high quality and a reduction in batch-to-batch variation.
“Sophisticated equipment for secondary processes can be integrated into the product line—for example, reeling or precision cut-to-length tubing,” said Gerding. “In-line laser marking of silicone tubes enables the utmost batch control at the component level, allowing customers to know, at any given moment, which product from which production lot is used in their application.”
OEMs are demanding robust and sustainable validation protocols for their product lines to ensure product consistency and quality along with regulatory compliance. Along with compliance, they also are focusing on contingency planning on legacy and new products as they are being developed.
“The earthquakes in Italy and Japan impacted the supply chain for several OEMs and they want to ensure that will not happen again on such a large scale,” said Donohue. “Our global footprint allows us to move manufacturing for dual-validated customers anywhere in the world as needed.”
Greater Functionality
OEM customers frequently design products that combine several different performance properties. A catheter, for example, needs a soft, flexible tip to navigate the arterial system, but also must have a stiff, reinforced proximal area so the surgeon can push the catheter into position in the body.
Teleflex Medical OEM recently introduced a new technology for joining dissimilar tubing segments without diminishing flexibility and other performance characteristics. The molding technique allows production of catheter shafts with tubing sections of different diameters, or the combination of rigid or reinforced segments with flexible tubing areas.
“It is an outstanding alternative for conventional bonding techniques that generally result in a rigid bond site and decreased catheter flexibility,” said Jim McCormack, manager of global marketing communications for Teleflex Medical OEM. “There is tremendous potential for using this process for valve or graft delivery systems, or interventional catheter designs requiring strong proximal sections.”
New advanced materials on the market include Raumedic’s medical-grade polytetrafluoroethylene (PTFE) Moldflon tubing, which combines PTFE properties and thermoplastic processing capabilities. PTFE Moldflon has physical characteristics that are very similar to standard PTFE, such as superior temperature and chemical resistance, low friction coefficient and tensile strength. Because PTFE Moldflon is pelletized, it can run continuously on standard extrusion lines, whereas traditional PTFE is a batch process and therefore non-continuous using ram extrusion lines.
“PTFE Moldflon can be run on micro-extrusion lines for ultra-thin wall thicknesses down to 0.0005 inches to produce inner catheter liners without the need to be drawn/necked down as necessary with standard PTFE,” said Gall.
Thermoplastic processing capabilities allow additional thermoforming operations on the tube, such as tipping and flaring, without showing common manufacturing-related issues such as shearing, cracking or flaking. It also can easily be co-extruded with barium sulfate stripes, which are widely used in catheter tubing for intravenous lines. Very fine platinum/iridium lead wires of 0.001 inches also can be coated with PTFE Moldflon, protecting their physical properties, according to the company.
In a new material development, researchers at Harvard University have developed a variation of SLIPS (slippery liquid-infused porous surfaces) surface technology that is compatible with medical devices. SLIPS distributes a liquid layer on a surface that repels a wide range of materials.
“Traditional SLIPS uses porous, textured surface substrates to immobilize the liquid layer, whereas medical surfaces are mostly flat and smooth, so we further adapted our approach by capitalizing on the natural roughness of chemically modified surfaces of medical devices,” said Joanna Aizenberg, who led the research team.
Adhering the SLIPS coating to medical devices is a two-step process that begins with attaching a monolayer of perfluorocarbon, a material similar to Teflon. A layer of liquid perfluorocarbon is then added to form a tethered perfluorocarbon and a liquid layer—together called a tethered-liquid perfluorocarbon surface (TLP). In addition to repelling a number of substances, including fibrin and platelets, the components of the blood that cause clotting, the TLP surface also prevented clot formation after being stored for a year under normal temperature and humidity conditions, and also remained stable when subjected to the shear stresses resulting from blood flow in catheters, central lines and dialysis machines. Moreover, the coating repelled bacteria and suppressed the formation of biofilm.
There also is growing interest in platinum-cured silicone materials, which use peroxide to prevent cross-contamination and improves the crosslinking of the silicone elastomers into polymers. Platinum serves as a catalyst to jump-start the curing process and does not result in unwanted byproducts that can leach out from the final polymer.
For example, Freudenberg Medical’s PharmaFocus Premium tubing product line is fabricated using a platinum-cured silicone raw material “specifically formulated to meet the demanding requirements of pharmaceutical and bioprocessing applications,” said Gerding. “It also delivers superior performance in high purity fluid transfer, as well as tube resilience and adaptability due to excellent flexibility.”
Future Challenges
Medical device companies and the U.S. Food and Drug Administration (FDA) want to eliminate risks to the end-user/patient. A top concern is the long-term biocompatibility of component materials. For example, companies increasingly are interested in replacing polyvinylchloride (PVC) tubing with alternative materials. The goal is to avoid chlorine-derived materials, which can pose environmental and health issues if not incinerated properly at high-enough temperatures. Another problem is the plasticizers—such as di-ethylhexyl phthalate (DEHP)—that are added to soften the PVC. Studies show these tend to migrate out from the tubing and into the drug fluid path or even into the blood path of patients, raising concerns about their biological impact.
Independent studies using nitroglycerin also have shown that PVC is prone to adsorbing drugs and critical drug components, which may interfere with the dosing accuracy of drugs supplied to the patient.
“Alternative materials to PVC could be thermoplastic elastomers (TPE) or polypropylene blends (PP),” said Gall. “TPEs, however, do not easily bond to other substrates, such as polycarbonate or acrylonitrile butadiene styrene connectors, which are widely used in standard IV tubing sets. Good bonding characteristics can be achieved with PP tubing using tetrahydrofuran; however both TPE and PP are expensive and don’t even come close to the production costs of PVC. Therefore, PVC will likely remain the material of choice until there is a political mandate to move away from PVC in the healthcare industry.”
Forward-thinking medical device companies that do business in the European Union, however, are looking for substitute materials now rather than later. Efforts to replace these plasticizers already have started in the Europe. For example, France has banned the use of DEHP from medical tubing used in pediatric, maternity and neonatal hospitals; this ban likely will extend to other medical devices in the near future.
“Device designers who proactively switch to a non-phthalate plasticizer for medical tubing applications will no longer have to worry about quickly adapting when regulatory requirements mandate the use of non-phthalate plasticizers in medical products,” Mark Brucks, market development representative for plasticizers at Chicago, Ill.-based Eastman Chemical Company, wrote in a blog on www.pddnet.com about a year ago. “There are several non-ortho-phthalate alternatives currently available, and regulatory and governmental bodies are actively reviewing and recommending materials for medical device use.”
Some device designers, he noted, already have made the switch to alternative plasticizers in some product lines in the United States, “but for those considering alternative materials for the development of new devices or the redevelopment of current devices, it is important to realize early in the process that replacing DEHP with an acceptable alternative will require a reformulation of the PVC compound being used to manufacture the device. This will ensure that the performance and appearance will be similar to the current devices. In addition, requalifications or re-certifications will be necessary in most instances.”
Bioabsorbable polymers such as poly-L-lactic acid and poly(lactic-co-glycolic acid) are rapidly gaining traction and will have a big impact on material selection for medical tubing. These materials are expensive, however, so tubing suppliers must fully understand their physical characteristics and how they are impacted or degraded by the extrusion process (for example, prolonged residence time).
“Concentricity—uniform wall thickness—of the tubing is also very critical,” said Gall. “Our micro extrusion lines are capable of running very low volumes of such expensive formulations, with minimal residence time.”
In the United States and around the world, regulatory agencies are requesting more detailed information about the materials in medical devices, including colorants. The FDA continues to push regulation further down the supply chain.
“Design control, along with specific product line validation, is the norm today and we only expect the regulations to get increasingly more stringent as newer devices are introduced into the marketplace,” said Donohue.
In recent years, more regulatory mandates have required engineering departments to do more, with equal or even fewer staff—which slows down the approval process. The FDA also is understaffed and finding it hard to deal with new technologies and advanced products.
“New product developments and market launches seem to take longer than in the past, which is a drawback to the U.S. medical device industry, especially when compared to the European market,” Gall pointed out. “It is not surprising that many companies now choose Europe as the place to launch their medical devices, rather than the U.S.”
Pushing the Envelope
OEMs are intensely focused on functionality, speed to market and cost.
As a result, tubing continues to push the envelope as more advanced materials and innovative technologies are developed.
Medical device manufacturers and their suppliers must stay on the leading edge of technology, material science and best practices to meet these evolving manufacturing challenges. Co-extrusion continues to advance its capabilities, allowing multiple materials to be combined in one tube that provide different properties.
For increasingly complex drug-delivery systems, Natvar has developed several unique and drug-specific co-extrusions that use up to five layers if needed. For example, a co-extruded product line can safely deliver dimethylsulfoxide in such a way that it does not absorb into the tube itself and holds up under long-term exposure, with no detectable tube degradation.
“These layers, or co-extrusions, are specialized to drive cost out, provide specific barrier protection as needed and ultimately provide a fluid path with superior protection from absorption and outside environmental factors such as moisture and oxygen,” said Donohue.
Many design engineers believe that more layers mean more cost, when in many cases it actually can be less costly and enhance the product’s performance from a quality and manufacturing perspective.
“For example,” said Donohue, “today there is a push for highly engineered resins to deliver greater stability and improved reliability. These materials are, however, expensive and can be difficult to process as a single mono-layer extrusion. Using co-extrusion, multi-layer technology can achieve the same—or sometimes better—results by combining lower-cost materials, to achieve the same results.”
From a downstream and collection standpoint, automation continues to play a critical role in the success of more complex, functional products because it generates consistent quality and improved repeatability—something that is harder to achieve as products become more complicated and expensive to make. Automation speeds up production and eliminates errors that drive up cost.
“Advancements in vision inspection equipment have allowed the industry to inspect, produce and package in a manner that was not possible just a few years ago,” said Donohue. “The introduction of high-speed extrusion lines combined with new crosshead technology allows for more complex structures to achieve highly engineered performance at lower cost.”
“Ultimately, understanding a customer’s requirements and the application is key for providing the best solution,” said Gerding. “Depending on the application, that solution can range from straightforward and cost-efficient to a more complex process with multiple value-added steps. Getting the tubing supplier involved early in product development, and maintaining effective feedback and communication throughout the production process, is essential for providing a value-added, sustainable solution to the client.”
Mark Crawford is a full-time freelance business and marketing/communications writer based in Madison, Wis. His clients range from startups to global manufacturing leaders. He also writes a variety of feature articles for regional and national publications and is the author of five books. Contact him at mark.crawford@charter.net.
With these technological and design goals in mind, OEMs more often count on their tubing vendors to turn their dreams into reality—to add features, reduce product size and reduce cost.
“Tubing is expected to fulfill more functions,” said Lars Gerding, director of technology for Freudenberg Medical, a Carpinteria, Calif.-based global manufacturer of precision molded components and tubing. “There is increased demand for more lumens with nonsymmetric cross sections, an increase in functionality with surface modification, or the incorporation of active additives, such as drugs or antimicrobial agents.”
Robert Donohue, general manager for Natvar, a Tekni-Plex company headquartered in Clayton, N.C., that provides medical tubing and profiles for medical device manufacturers, expects the trend toward minimally invasive surgical device development (including unique fluid-path delivery systems) to continue to accelerate.
“We are increasingly being asked to help our customers design products for delivering highly engineered medications for deposable medical devices that require precise dosing levels, or specific environmental protection against moisture, light, heat or oxygen,” said Donohue.
Another reason for increased miniaturization is the growing trend toward medical device connectivity, where data is transferred from the medical device/patient to an analytical or diagnostic system. This capability allows for the prognostic and strategic medical care of patients, with the benefit of immediate treatment and/or prevention of critical health issues. For example, intracranial brain pressure catheters often consist of a single lumen implant-grade polyurethane catheter protecting the wiring leading to a microchip embedded in a stainless steel tip at the distal end of the catheter. This microchip measures brain pressure, oxygen levels and temperature levels inside the brain of severely injured trauma patients.
“The increasingly advanced neurological and neurovascular devices coming into the market show how thermoplastic polymers, metals and electronics are combined into one product,” said Rudi Gall, managing director for Raumedic, a Leesburg, Va.-based provider of extrusion/tubing, molding, and assembly services to the medical device industry. “Metal wires or cables can be embedded inside tubing walls or are run inside the inner lumen of the tubing to allow for electronic data transfer and transmission from the medical device/patient.”
Top Quality, Tight Tolerances
OEMs have high expectations when it comes to quality and tight tolerances. For example, tubing can get as small as 0.1 millimeters (mm)— 0.004 inch—interior diameter (ID) with a tolerance of 0.0005 inches—a fraction of the size of a human hair. Coil-reinforced catheter sizes can be as small as 1 Fr. Tolerances can be equally impressive for larger catheter shafts. For example, Teleflex Medical OEM, a Gurnee, Ill.-based global provider of custom-engineered medical components, including tubing, catheters and balloons, can make a large-diameter (35 Fr), lined, reinforced catheter shaft with a wall thickness as thin as 0.008 inches with ID tolerance at +/-.002 inches and outer-diameter (OD) tolerance at +/-.002 inches. For an fluorinated ethylene propylene/ethylene tetrafluoroethylene-lined, large-diameter, braided shaft, wall thicknesses can be as thin as 12 Fr (.0055 inches).
Medical device manufacturers also count on the raw-material expertise of their vendors to deliver the materials they need to meet the performance specifications of their products. Requirements range from simple, cost-driven ID/OD high runner to precision cut-to-length tubing with complex cross sections and value-added steps, like skiving, hole punching and drilling.
“Depending on the final application, more customers are also seeking highly sophisticated sub-assemblies, plus connectors or tip forming,” said Gerding.
OEMs also want their suppliers to have control over variability and assure the lot-to-lot consistency of their tubing so the overall device assembly process remains robust. This requires the availability of statistical process data and a closed-loop controlled extrusion process, which can be achieved through in-line measurement systems such as laser microscopes measuring the outer diameter of a tubing and ultrasound to measure the wall thickness.
“Having a stable quality system in place, understanding the market requirements of the medical device and technology market and providing other value-added capabilities is essential for any tubing vendor to become a trusted partner,” said Gall.
Tight tolerances also are essential to verification and validation, helping to create a smoother path to regulatory compliance. This especially is true for more complex products, including miniaturized devices and combination products. Achievements made in extrusion lines and related auxiliary equipment allow better process control with in-line inspections, resulting in consistent high quality and a reduction in batch-to-batch variation.
“Sophisticated equipment for secondary processes can be integrated into the product line—for example, reeling or precision cut-to-length tubing,” said Gerding. “In-line laser marking of silicone tubes enables the utmost batch control at the component level, allowing customers to know, at any given moment, which product from which production lot is used in their application.”
OEMs are demanding robust and sustainable validation protocols for their product lines to ensure product consistency and quality along with regulatory compliance. Along with compliance, they also are focusing on contingency planning on legacy and new products as they are being developed.
“The earthquakes in Italy and Japan impacted the supply chain for several OEMs and they want to ensure that will not happen again on such a large scale,” said Donohue. “Our global footprint allows us to move manufacturing for dual-validated customers anywhere in the world as needed.”
Greater Functionality
OEM customers frequently design products that combine several different performance properties. A catheter, for example, needs a soft, flexible tip to navigate the arterial system, but also must have a stiff, reinforced proximal area so the surgeon can push the catheter into position in the body.
Teleflex Medical OEM recently introduced a new technology for joining dissimilar tubing segments without diminishing flexibility and other performance characteristics. The molding technique allows production of catheter shafts with tubing sections of different diameters, or the combination of rigid or reinforced segments with flexible tubing areas.
“It is an outstanding alternative for conventional bonding techniques that generally result in a rigid bond site and decreased catheter flexibility,” said Jim McCormack, manager of global marketing communications for Teleflex Medical OEM. “There is tremendous potential for using this process for valve or graft delivery systems, or interventional catheter designs requiring strong proximal sections.”
New advanced materials on the market include Raumedic’s medical-grade polytetrafluoroethylene (PTFE) Moldflon tubing, which combines PTFE properties and thermoplastic processing capabilities. PTFE Moldflon has physical characteristics that are very similar to standard PTFE, such as superior temperature and chemical resistance, low friction coefficient and tensile strength. Because PTFE Moldflon is pelletized, it can run continuously on standard extrusion lines, whereas traditional PTFE is a batch process and therefore non-continuous using ram extrusion lines.
“PTFE Moldflon can be run on micro-extrusion lines for ultra-thin wall thicknesses down to 0.0005 inches to produce inner catheter liners without the need to be drawn/necked down as necessary with standard PTFE,” said Gall.
Thermoplastic processing capabilities allow additional thermoforming operations on the tube, such as tipping and flaring, without showing common manufacturing-related issues such as shearing, cracking or flaking. It also can easily be co-extruded with barium sulfate stripes, which are widely used in catheter tubing for intravenous lines. Very fine platinum/iridium lead wires of 0.001 inches also can be coated with PTFE Moldflon, protecting their physical properties, according to the company.
In a new material development, researchers at Harvard University have developed a variation of SLIPS (slippery liquid-infused porous surfaces) surface technology that is compatible with medical devices. SLIPS distributes a liquid layer on a surface that repels a wide range of materials.
“Traditional SLIPS uses porous, textured surface substrates to immobilize the liquid layer, whereas medical surfaces are mostly flat and smooth, so we further adapted our approach by capitalizing on the natural roughness of chemically modified surfaces of medical devices,” said Joanna Aizenberg, who led the research team.
Adhering the SLIPS coating to medical devices is a two-step process that begins with attaching a monolayer of perfluorocarbon, a material similar to Teflon. A layer of liquid perfluorocarbon is then added to form a tethered perfluorocarbon and a liquid layer—together called a tethered-liquid perfluorocarbon surface (TLP). In addition to repelling a number of substances, including fibrin and platelets, the components of the blood that cause clotting, the TLP surface also prevented clot formation after being stored for a year under normal temperature and humidity conditions, and also remained stable when subjected to the shear stresses resulting from blood flow in catheters, central lines and dialysis machines. Moreover, the coating repelled bacteria and suppressed the formation of biofilm.
There also is growing interest in platinum-cured silicone materials, which use peroxide to prevent cross-contamination and improves the crosslinking of the silicone elastomers into polymers. Platinum serves as a catalyst to jump-start the curing process and does not result in unwanted byproducts that can leach out from the final polymer.
For example, Freudenberg Medical’s PharmaFocus Premium tubing product line is fabricated using a platinum-cured silicone raw material “specifically formulated to meet the demanding requirements of pharmaceutical and bioprocessing applications,” said Gerding. “It also delivers superior performance in high purity fluid transfer, as well as tube resilience and adaptability due to excellent flexibility.”
Future Challenges
Medical device companies and the U.S. Food and Drug Administration (FDA) want to eliminate risks to the end-user/patient. A top concern is the long-term biocompatibility of component materials. For example, companies increasingly are interested in replacing polyvinylchloride (PVC) tubing with alternative materials. The goal is to avoid chlorine-derived materials, which can pose environmental and health issues if not incinerated properly at high-enough temperatures. Another problem is the plasticizers—such as di-ethylhexyl phthalate (DEHP)—that are added to soften the PVC. Studies show these tend to migrate out from the tubing and into the drug fluid path or even into the blood path of patients, raising concerns about their biological impact.
Independent studies using nitroglycerin also have shown that PVC is prone to adsorbing drugs and critical drug components, which may interfere with the dosing accuracy of drugs supplied to the patient.
“Alternative materials to PVC could be thermoplastic elastomers (TPE) or polypropylene blends (PP),” said Gall. “TPEs, however, do not easily bond to other substrates, such as polycarbonate or acrylonitrile butadiene styrene connectors, which are widely used in standard IV tubing sets. Good bonding characteristics can be achieved with PP tubing using tetrahydrofuran; however both TPE and PP are expensive and don’t even come close to the production costs of PVC. Therefore, PVC will likely remain the material of choice until there is a political mandate to move away from PVC in the healthcare industry.”
Forward-thinking medical device companies that do business in the European Union, however, are looking for substitute materials now rather than later. Efforts to replace these plasticizers already have started in the Europe. For example, France has banned the use of DEHP from medical tubing used in pediatric, maternity and neonatal hospitals; this ban likely will extend to other medical devices in the near future.
“Device designers who proactively switch to a non-phthalate plasticizer for medical tubing applications will no longer have to worry about quickly adapting when regulatory requirements mandate the use of non-phthalate plasticizers in medical products,” Mark Brucks, market development representative for plasticizers at Chicago, Ill.-based Eastman Chemical Company, wrote in a blog on www.pddnet.com about a year ago. “There are several non-ortho-phthalate alternatives currently available, and regulatory and governmental bodies are actively reviewing and recommending materials for medical device use.”
Some device designers, he noted, already have made the switch to alternative plasticizers in some product lines in the United States, “but for those considering alternative materials for the development of new devices or the redevelopment of current devices, it is important to realize early in the process that replacing DEHP with an acceptable alternative will require a reformulation of the PVC compound being used to manufacture the device. This will ensure that the performance and appearance will be similar to the current devices. In addition, requalifications or re-certifications will be necessary in most instances.”
Bioabsorbable polymers such as poly-L-lactic acid and poly(lactic-co-glycolic acid) are rapidly gaining traction and will have a big impact on material selection for medical tubing. These materials are expensive, however, so tubing suppliers must fully understand their physical characteristics and how they are impacted or degraded by the extrusion process (for example, prolonged residence time).
“Concentricity—uniform wall thickness—of the tubing is also very critical,” said Gall. “Our micro extrusion lines are capable of running very low volumes of such expensive formulations, with minimal residence time.”
In the United States and around the world, regulatory agencies are requesting more detailed information about the materials in medical devices, including colorants. The FDA continues to push regulation further down the supply chain.
“Design control, along with specific product line validation, is the norm today and we only expect the regulations to get increasingly more stringent as newer devices are introduced into the marketplace,” said Donohue.
In recent years, more regulatory mandates have required engineering departments to do more, with equal or even fewer staff—which slows down the approval process. The FDA also is understaffed and finding it hard to deal with new technologies and advanced products.
“New product developments and market launches seem to take longer than in the past, which is a drawback to the U.S. medical device industry, especially when compared to the European market,” Gall pointed out. “It is not surprising that many companies now choose Europe as the place to launch their medical devices, rather than the U.S.”
Pushing the Envelope
OEMs are intensely focused on functionality, speed to market and cost.
As a result, tubing continues to push the envelope as more advanced materials and innovative technologies are developed.
Medical device manufacturers and their suppliers must stay on the leading edge of technology, material science and best practices to meet these evolving manufacturing challenges. Co-extrusion continues to advance its capabilities, allowing multiple materials to be combined in one tube that provide different properties.
For increasingly complex drug-delivery systems, Natvar has developed several unique and drug-specific co-extrusions that use up to five layers if needed. For example, a co-extruded product line can safely deliver dimethylsulfoxide in such a way that it does not absorb into the tube itself and holds up under long-term exposure, with no detectable tube degradation.
“These layers, or co-extrusions, are specialized to drive cost out, provide specific barrier protection as needed and ultimately provide a fluid path with superior protection from absorption and outside environmental factors such as moisture and oxygen,” said Donohue.
Many design engineers believe that more layers mean more cost, when in many cases it actually can be less costly and enhance the product’s performance from a quality and manufacturing perspective.
“For example,” said Donohue, “today there is a push for highly engineered resins to deliver greater stability and improved reliability. These materials are, however, expensive and can be difficult to process as a single mono-layer extrusion. Using co-extrusion, multi-layer technology can achieve the same—or sometimes better—results by combining lower-cost materials, to achieve the same results.”
From a downstream and collection standpoint, automation continues to play a critical role in the success of more complex, functional products because it generates consistent quality and improved repeatability—something that is harder to achieve as products become more complicated and expensive to make. Automation speeds up production and eliminates errors that drive up cost.
“Advancements in vision inspection equipment have allowed the industry to inspect, produce and package in a manner that was not possible just a few years ago,” said Donohue. “The introduction of high-speed extrusion lines combined with new crosshead technology allows for more complex structures to achieve highly engineered performance at lower cost.”
“Ultimately, understanding a customer’s requirements and the application is key for providing the best solution,” said Gerding. “Depending on the application, that solution can range from straightforward and cost-efficient to a more complex process with multiple value-added steps. Getting the tubing supplier involved early in product development, and maintaining effective feedback and communication throughout the production process, is essential for providing a value-added, sustainable solution to the client.”
Mark Crawford is a full-time freelance business and marketing/communications writer based in Madison, Wis. His clients range from startups to global manufacturing leaders. He also writes a variety of feature articles for regional and national publications and is the author of five books. Contact him at mark.crawford@charter.net.