UNL researcher taps world-class 3D printers to make dissolvable medical implants

October 10, 2018

Michael Sealy still has the two metal screws in his elbow, the ones a surgeon used to repair the arm he broke when he fell back in fifth grade.

But Sealy, an assistant professor of mechanical and materials engineering at the University of Nebraska-Lincoln, wants to reformulate such souvenirs of accidents past so that they’ll slowly dissolve after they’ve done their job.

The idea behind creating dissolving medical implants is to eliminate the need for follow-up surgeries to remove screws, pins and plates. While it’s not clear how often that happens, Sealy said one orthopedic surgeon told him that he removes clavicle plates about half the time. In women, they can run afoul of bra and purse straps.

“Instead of having a permanent material in there, let’s have one that degrades,” Sealy said. He notices that his now-healed elbow sometimes hurts when the weather turns cold or a storm front moves in. He also feels it when he’s carrying groceries.

In his efforts, Sealy is using what’s billed as the first 3D printer in the world that combines the ability to use multiple materials and manufacturing processes while also printing highly reactive metals such as magnesium.

Magnesium is a mineral that’s abundant in the body, particularly in the bones. Yet it degrades quickly when exposed to oxygen, water and salts, which also are abundant in the body.

To reinforce magnesium long enough to do its job, Sealy began experimenting with a technique called laser shock peening while a graduate student at the University of Alabama. It’s similar to using a hammer to forge metal, making it harder and stronger.

Eventually, Sealy decided that he would need to apply the peening process all the way through the parts if he wanted to stop them from degrading, not just on the surface.

“That would give me control over corrosion for the entire life of the part, not just initially,” he said.

Enter UNL’s uber high-tech 3D printers, which allow researchers not only to print metals but also to use other manufacturing treatments in between, including laser shock peening. The printers also eliminate almost all of the oxygen, moisture and other impurities that could react with magnesium.

So far, Sealy has combined the two processes on easier-to-use metals: steel, titanium and aluminum. He plans to begin making magnesium implants next year.

Ultimately, the goal is to make implants that degrade at different rates inside the body. A fifth-grader, whose bones are growing quickly, would need implants that degrade more quickly than a 75-year-old woman. While there some degradable polymer implants already available, they don’t have the strength needed to repair a long bone like a femur.

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