Permanent magnets have long played a role in the medical industry. Examples of their applications include bodily use both internally and externally, motors for medical devices, and sensors. We continue to see a wide variety of uses for magnets in the medical industry, and the innovation associated with today’s research and technology is as advanced as ever.
While each application is unique, we see common themes that we work through with each of our customers. Developing a working partnership from the design and development phase, all the way through production, provides valuable insight and collaboration that results in the best final product.
Product Application & Confidentiality
Most medical customers start with an idea or concept that they anticipate will be patented at some point, and warrants a mutual non-disclosure agreement (NDA) as discussions begin about the magnetics portion. Even without knowing the final application of the magnet, we have successfully worked with medical customers on the design to prepare the part for production.
We respect and protect the intellectual property (IP) of our customers and understand that the incubation period for a new product can take a long time, with many changes and continuous data collection along the way. While it can be challenging for us not to know the final application, we can still work through the requirements of the magnet or magnetic assembly to provide the correct simulations and optimized design before the first prototype is built.
However, we also understand that the simulations and optimizations get close to the final design — but there is no substitution for building prototypes and testing the actual design.
For Use in the Body
Magnets used in the body take on requirements far beyond a “regular” magnet application. Here are considerations we discuss with our medical customers for these applications.
Coatings
The FDA requires coatings that are biocompatible for medical magnets that are in contact with the body. For magnets, the approved coatings include gold, parylene, titanium, and rhodium. Correct coatings assist with corrosion resistance to certain chemicals and are also safe for internal use.
Magnet Size
Almost all magnets for use in the body are small. Since a stronger magnet is required, neodymium is almost always used. Occasionally we encounter an application that asks a magnet to perform beyond what is physically possible — for example, a tiny 0.5 mm × 1 mm cylinder providing 20 lbs. of holding force, or a sensor reading 4,000 gauss from a 1 mm × 1 mm disc at 3″ of distance.
It is important to know what is realistically possible at a given size, the acceptable tolerances (try not to over-tighten if not required), and the outcome needed.
Magnet Shape and Magnetic Orientation
Magnet shape is usually dependent upon the application and the required outcome. Most magnets used inside the body tend to be small and cylindrical, while magnets used outside of the body take on many shapes and sizes.
Just as important as the shape is the direction of magnetization. For example, one application we helped design had the magnet passing over a sensor. The initial design showed the magnet with an axial direction of magnetization, but once we learned more about the sensor we realized that the direction of magnetization should be diametrical. Once corrected, the sensor and magnet worked great as a team.
Temperature, Cleaning, and Chemicals
Magnets will last indefinitely — well, almost — if the correct magnet and coating are selected based upon the temperature, cleaning, and chemicals to which they will be exposed. Neodymium magnets come in many grades, so selecting the correct grade to handle the temperature requirement is a good starting point.
Once the correct grade is determined, the environment to which the magnet will be exposed should be outlined. If a magnet will be cleaned with common chemicals or put in sterilization equipment, then a coating able to withstand this environment will be important. Outline any area where a magnet can encounter more than ambient air.
Documentation, Data Collection, and FDA Requirements
Testing, testing, and more testing. Data collection, more data collection, and even more data collection. We understand the time and effort it takes to go from concept to an FDA-approved product, and we continually invest in and upgrade our technical and manufacturing capabilities to support customers from prototype to production.
Each customer works with us to provide the list of documentation and reports required for each lot. Knowing what documentation and testing is needed during initial validation and production allows us, as the supplier, to develop the correct testing procedures, manufacturing processes, and a checklist of required documentation before mass production begins.
Engineering Support
The topics above are only a starting point when considering using magnets in medical applications. Advancements in medical technology continue to challenge us to push the boundaries of magnets, magnet assemblies, magnetic circuits, and coatings — for short-term surgical use, long-term implantation, and precision sensing and motor applications.
For prototyping with biocompatible coated magnets such as parylene and gold, see our eCommerce division SuperMagnetMan.