Finish the job: How miniaturisation is affecting coating and finishing
Jay Tourigny, senior vice president of MicroCare Medical explores how the trend towards miniaturisation is affecting coating and finishing decisions.
While the health care industry has had a long-standing reputation of being slow to adopt change, there’s been a recent shift that’s brought about new innovative thinking. One example where this is prominent is within medical device design. Patients have been demanding smaller and more portable devices which has created new challenges for designers and engineers. They must now consider new options and application methods for product finishing, as well as how to properly clean them to meet the strict guidelines.
Innovative cleaning offers a solution
It’s important that the cleaning methods of medical device components meet the highest standards of cleanliness as it can impact device performance and ultimately, any steps in the finishing process. This can be challenging as some traditional processes like water cleaning, for example, can leave behind spots. Also, water’s high surface tension inhibits its ability to reach, and therefore clean, small interior and intricate spaces.
There have been recent advances in cleaning fluids which offer more options for cleaning complex components. They are not only effective at satisfying the strict regulatory requirements needed in medical component manufacturing, but they also meet environmental standards and can provide an overall lower cost-per-part cleaned.
Lubricants to manage stacked tolerances
Guaranteeing device performance is important, equally as important is knowing that the lubricating material will not migrate into the human body. Many medical device manufacturers are finding great success with using polytetrafluoroethylene (PTFE), or “dry” lubricants, as opposed to traditional silicone lubricants as it stays on the instrument and does not transfer to the patient. It also can lubricate for multiple actuations and can be annealed to the instrument (substrate) so that it is semi-permanent. PTFE also can effectively address the issue of stiction (the combination of sticking and friction). Some surgical and medical procedural equipment is actuation-based, such as surgical staplers. This increases friction and mechanical movement requiring lubrication to eliminate stiction to ensure continued smooth movement.
Also, recent design incorporates single use devices created to be minimally invasive to the patient. These however are more complex with many small parts. The higher the part count, the more likely ‘stacked tolerances’ will become an issue. This occurs when the tolerances of individual components “stack up” against each other and effect the performance of the device. Stacked tolerances can also be commonplace when dealing with multi-part mechanical assemblies with moving parts. One option to address this is to design everything with tighter tolerances; however, this results in higher production costs. Alternatively, lubrication can be used on the components to reduce movement friction and minimize actuation forces.
Finishing touches
The changes in medical device design have created new challenges and opportunities for innovative finishing options. There are now more application methods which are solving these problems:
- Dipping: Frequently used in high volume production, the benefits include consistency and uniformity in coating nearly any external and internal surfaces. Small parts, coils of wires and unique geometries can be coated via this method.
- Wiping or brushing: Covering longer, ongoing surfaces including rods, tubing or sheeting can be accomplished through wiping or brushing. It can also be used if only small, select areas of a larger part requires coating.
- Spraying: Requires equipment such as a hand-held spray gun or automatic spray heads to apply diluted dispersions. Spraying can be used on a variety of devices. It is also more selective than dipping since material can be applied to small areas with more precision.
Carrier fluids to consider
Just as important as a good lubricant is a good carrier fluid when necessary for dilution and application. For example, medical grade silicone is provided in concentrated form, so a carrier fluid must be used to dilute the lubricant, allowing for a very thin film of silicone to be applied to a surface.
Previously, carrier fluids posed safety and environmental concerns, for example flammability. Commonly used silicones do not work well with carrier fluids that are low in flammability or toxicity. These carrier fluids featured improved safety and environmental profiles, but the amount of silicone that they could be mixed in was only 1-2%, far lower than the threshold required for most medical devices. Advancements in carrier fluid chemistries have produced medical grade formulas with nonpyrogenic properties, ISO 10993 certification and full compatibility with sterilising processes. Plus, there are very few toxicity or handling issues with PTFE materials.
The answer’s out there
While there are many trends impacting today’s medical device design, it’s important to consider their implications on product finishing in order to select the best, most cost-effective solution. Today’s cleaning fluids, lubricants and coatings have come a long way, and innovations have kept pace with trends in miniaturization, automation and application. By examining factors like safety, application method and overall effectiveness, you can make confident decisions about which solutions will work best for your needs.