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Designing Fluid Path Products for Incremental Innovation

 With ongoing technological advances in materials and manufacturing processes, it should come as no surprise that innovation is a megatrend currently extending across various industries. However, because of the impending Affordable Care Act, the medical device tax, efforts to create a unique device identification system, and other building cost pressures, there is the fear that medical device innovation could be stifled. But the changes in policy don’t have to mean expensive, risky changes to product development.

 With ongoing technological advances in materials and manufacturing processes, it should come as no surprise that innovation is a megatrend currently extending across various industries. However, because of the impending Affordable Care Act, the medical device tax, efforts to create a unique device identification system, and other building cost pressures, there is the fear that medical device innovation could be stifled. But the changes in policy don’t have to mean expensive, risky changes to product development. As medical device manufacturers look ahead, they can apply the methods such as incremental innovation and design for manufacturing to yield value in existing and new product lines. 

This article explores the latest trends in fluid path components such as silicone tubing, and assesses material formulation, manufacturing processes, and testing methods. Understanding these trends can help designers produce meaningful advances without requiring significant investments in potentially risky processes.

Advances in Material Formulation

Global regulations are driving some advances in medical device materials. Developed to safeguard human health and the environment from risks associated with hazardous chemicals, the European Union’s Registration, Evaluation, Authorization, and Restriction of Chemicals (REACh) has restricted the use of di (2-ethylhexyl) phthalate (DEHP) in medical devices. DEHP is a plasticizer that can be used in fluid path components, including IV tubes and bags to make the base material pliable. Other restricted materials include bisphenol-A (BPA), used in the high performance plastics common in medical device component manufacturing. In some segments of the medical device market manufacturers are looking to replace PVC altogether as they anticipate future trends and regulations. The fear of having to requalify and revalidate products due to material changes up and down the value chain is forcing companies to take a much longer range approach to supplier and material selection.

Rather than creating new material alternatives from scratch, which can be difficult to get approved by FDA, many medical device manufacturers are looking to existing materials, such as silicone or thermoplastic elastomers (TPEs). These materials can be custom compounded to meet fluid path application needs. There are no restrictive regulations and silicone offers a clean alternative to substances of concern that are regulated for fluid path components. Custom compounding, while not a novel concept, can provide unique designs without including materials of concern, such as DEHP and BPA.

 
Molding processes can be improved through automation techniques.

Custom compounding can be used to formulate application-specific performance silicone or TPEs, with tighter control and just the right performance properties including tear strength, compression set, elongation, modulus, and durability. Keep in mind, it is virtually impossible to optimize all properties. Custom compounding focuses on developing the right balance of performance for a specific application. By reducing the tolerance range on key physical properties, manufacturers are able to target certain properties to meet their needs, rather than unnecessarily striving to develop the holy grail of polymeric materials. For example, additives can be used to develop gamma resistant (GR) silicone compounds to create medical valves that prevent sealing or rehealing when exposed to high levels of gamma sterilization, and maintain an effective fluid path throughout their life cycle. Additives can also be used to develop antimicrobial silicone compounds that can ensure patient safety. In addition, TPEs can be used as a viable PVC replacement material for fluid path delivery applications.

Manufacturing Methods for Performance

The ongoing pressure to cost-effectively improve product performance and quality is what drives advances in manufacturing processes. The current trend towards complex component minimization is increasing the need for advances on the production line. Automation innovations can provide two of the most important elements in medical device manufacturing—consistency and precision. 

Advanced automated manufacturing processes now allow fluid path OEMs and component suppliers to reduce variation from production run to production run, ensuring consistency over the life of the product. For molded components, the use of automation can be found throughout the process and lights-out manufacturing (completely automated) has become a reality for many molded components. 

Further advances in automated part handling have led to incremental innovations such as two-shot molding and micromolding. In silicone to thermoplastic two-shot molding, thermal management is vital to successful production. The cold thermoplastic tool needs to be isolated from the hot silicone tool, and all the carefully calculated shrink rates depend on constant control of temperatures in the mold area. Consistent part transfer times between molds, or automatically rotating molds, are necessary to maintain this thermal balance.

Micromolding capabilities allow manufacturers to produce small components for minimally invasive surgical procedures with increased precision and decreased variability. It is necessary for manufacturers to look for precisely controlled, automated part handling options because the components are often too minute to be handled manually. Air movement from HVAC or air filtration systems, or even a static electrical charge, can significantly disrupt part transfer from molding to packaging. 

Advances in extrusion technology have led to microbore tubing.

These advances do not apply to molded components only. Automation is a critical part of the extrusion process as well. Closed loop feedback systems that measure critical parameters during production can be used to automatically adjust the process resulting in lower dimensional variation in finished parts. Improved automation and precision also enables an expanded range of small diameter or microbore tubing that supports the trend towards minimally invasive surgery.

UV curing is another recent advance for which innovations in material engineering and manufacturing come together to improve fluid path components. Specialized additives and inhibitors within the compound enable faster cure using less energy for products coming off the line. With such materials, UV curing is almost instantaneous, allowing for dramatic increases in extrusion rates. For example, in two-shot molding (e.g., a silicone and thermoplastic) manufacturers were historically required to use an engineered thermoplastic to withstand the high temperatures used to cure the silicone. Innovations in UV curable silicones enable manufacturers to potentially use lower cost thermoplastic materials. 

In addition, automation helps maintain the purity of cleanroom operations. Common in fluid path component extrusion and molding, cleanrooms must be kept sterile and contaminant-free to ensure patient safety. Finally, automation is being used to improve product quality through automatically inspecting and testing components. Imperfect products are rejected before they reach the customer, and more importantly, the patient.

Measurement is Key

Incremental innovations in manufacturing are yielding new processes, like minimization. However, it is not enough to simply develop an innovative method to make a part. Manufacturers must be able to verify the process and ensure overall quality. Improvements in metrology, and data collection and analyses are a critical part of incremental innovation.

Vision systems used to detect defects before they are passed along to the patient are typical in-process measurement tools. Many engineering groups are replacing optical comparators with advanced vision systems that include programmable automated measurement capabilities—further evidence that vision inspection systems are a critical part of the design and measurement process of molding parts. These types of visual inspection systems are more complex as components become smaller and more advanced. In extrusion processes, x-ray systems provide improved measurement of critical dimensions during the production process.

Crunching the Numbers

All the high-tech inspection and measurement tools in the world are hardly worth the investment if the data are not utilized properly. Understanding how to analyze and treat data to detect trends and optimize processes is key. Although Six Sigma-related processes exist to analyze data and identify variations, advanced modeling software is being developed for extruded components. Eventually the software could be used to predict performance of the full system based on varying properties in the components, particularly where solid components come into contact with fluids. Imagine a system model for use in peristaltic pump applications that can virtually assess and adjust key variables contributing to consistent flow rate. This type of technology is still in its infancy. However, continued progress, such as in advanced modeling systems, will help manufacturers all along the supply chain to better understand how different aspects of a medical device work together to improve performance.

Conclusion

Refining rather than revolutionizing seems to be the trend today as progress meets economic realities. Incremental innovation is bringing big value to the overall medical device component manufacturing process from advances in material formulation to manufacturing processes, including new ways to consider data collection and analysis. 

Through custom compounding, high-performance materials such as silicones are being formulated to not only meet fluid path component performance needs, but to replace materials of concern. Manufacturing processes are also becoming more advanced, increasing speed, consistency, and precision of parts that are becoming smaller and more complex. Finally, keeping pace with parallel advances throughout the supply chain, innovative test methods and validation processes are ensuring product quality and enabling future innovations in component and device design. 

Fluid path OEMs and component manufacturers are faced with the unique opportunity to work together and spur incremental innovation from material formulation to the product line to design and manufacture the most advanced devices that provide best patient care possible.

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Robert D. Schwenker is a business manager for Saint-Gobain Performance Plastics, based in Austin, TX. He has worked in the healthcare market group for 10 years in new product development and business management. Schwenker has a chemical engineering degree from Cornell University and an MBA from the University of Texas.

Aaron Updegrove is marketing manager in the healthcare markets segment of with Saint-Gobain Performance Plastics, based in Portage, WI. He has more than 18 years of experience in sales and marketing for companies that produce engineered materials and components. Updegrove holds a mechanical engineering degree from Marquette University. 

 
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