Metals Used in Medical Product Design
Do you know the 6 most important metals used for medical devices? Let’s dig around and see if we can’t uncover some precious nuggets – of wisdom!
Hello, I’m Gordon Styles, the founder and CEO of Star Rapid, and I’ve been involved in rapid prototoyping and new product development for over 35 years. Today I’m just tickled pink to welcome you all once again to another episode of Serious Engineering for Serious Engineers.
You know, I’m a busy man. And when I’m not training on my secret island fortress to combat the forces of evil, I often find myself fielding questions about the right materials to use for certain types of products.
Recently we’ve had a lot of enquiries about medical devices and the best way to design for them, so I thought now would be the right time to offer some insights about this subject.
But before we go into that, let’s clear up a common misunderstanding. All medical products are classified based on their application and their potential risk to human health – not on the material that they’re made from.
Still, these six metals have proven themselves in the fields of medicine and healthcare over the years. We’re confident that the following information can be beneficial to product developers of all kinds, not just for medical products, so let’s get started.
- Stainless Steel
What makes stainless steel stainless? Well, generally speaking, it’s the addition of at least 11% chromium to mild steel that prevents it from rusting or forming iron oxide, but this number can go as high as 20%. There are many different formulas with different amounts of corrosion resistance, tensile strength and more.
The most common types of stainless steel used for medical implants and body piercings are 316 and 316L, for low carbon. Both types are highly corrosion resistant. This is important because corrosion in the bloodstream can cause infection and possibly even death. Many people also suffer from allergic reactions to nickel, so low-nickel varieties of stainless steel can be substituted.
Many surgical tools are made from either 440 or 17-4 PH stainless. They can be heat treated to various degrees of hardness to make sharp-edged instruments.
Stainless steel is commonly used for orthopedics such as replacement hip joints, or screws and plates used to stabilize broken bones. And it’s found in surgical tools like tweezers, forceps, and hemostats because it’s strong and durable while being easy to clean and sterilize.
Copper is rarely used directly for medical implants. This is because copper is soft and may cause toxicity inside of human tissue. But copper alloys are sometimes found in dental implants, and to prevent infection in bone transplant operations.
Copper really shines because of its outstanding antiviral and antibacterial properties. Even the ancient Egyptians and Assyrians knew this, which is why they kept their drinking water in copper pots to prevent the growth of algae and bacteria.
We know that copper is an ideal material for surfaces that are constantly being touched, like door handles, bed rails and switches. And this property works not only for solid copper but also copper plating or even copper-based paints and powder coats.
In fact, it’s so useful in this regard that more than 400 different copper alloys have been approved by the FDA as biocidal to prevent the spread of viruses like Covid19 – the only raw material to be so designated.
Titanium is now a common substitute for stainless steel in skeletal supports and bone replacements. It’s stronger and more durable than stainless (though not as flexible) while being substantially lighter, and it demonstrates excellent biocompatibility.
One of the nice properties of titanium is that it can be metal 3D printed to create perfectly customized parts using scans and X-rays of the patient’s exact anatomical structure. Plus, it sounds pretty cool when you tell people that your skull is made of titanium. I know. Believe me, I know.
- Cobalt Chrome
Cobalt chrome has high wear resistance so it’s great for joint replacements as well as dental implants.
It can also be electropolished, making the surface so smooth that it’s hard for contamination to build up.
Cobalt chrome parts can be CNC machined, 3D printed and turned into endoskeletons for unstoppable killing machines from the future.
While seldom used in direct contact with the body, aluminium is very commonly employed for various types of support equipment that must be light, strong, and corrosion resistant.
Examples include bed frames, wheelchairs, walking sticks, orthopedic supports and IV stands. But since raw aluminium can tarnish or oxidize very easily, aluminium parts are typically painted, plated, or anodized for durability.
Magnesium has an excellent strength-to-weight ratio and it’s biosafe, but it’s not typically used for medical devices or appliances. Why not? Well, because it’s highly reactive when exposed to oxygen or different liquids unless it’s been surface treated.
There is a plus side though. The tendency of magnesium to biodegrade naturally and safely (for example, with chewable magnesium tablets) can be cleverly exploited to make heart stents and bone graft replacements. A magnesium stent can be reabsorbed into the bloodstream after vascular surgery, helping to prevent another surgical procedure to remove the stent at a later time. And that’s a good thing.
Other common metals used in small amounts include gold, platinum, silver, iridium, and tungsten.
Engineers and applied scientists are constantly looking for new and improved materials to support advanced medical procedures, but these six continue to demonstrate their worth. Know one that we missed? Be sure to drop us a comment below.
Ok, that’s our episode for today. Don’t forget to ring the bell, like us and subscribe. And we’ll see you next time for more Serious Engineering for serious engineers.