The case for metal replacement in medical devices

Lightweighting, cost reduction and user safety are among the reasons that plastics increasingly are becoming the material of choice for medical devices, reports Ann R. Thryft, Senior Technical Editor, Materials & Assembly, at sister brand DesignNews. She has just published a well-documented article on the continuing trend toward metal replacement and, interestingly, the development of metal/plastic hybrids in the medical technology space.

The plague of hospital-acquired infections made headlines again recently when it was revealed that a contaminated duodenoscope, a type of endoscope, used at the UCLA Ronald Reagan Medical Center exposed almost 200 patients to an antibiotic-resistant superbug and contributed to the death of two people. Back in March, PlasticsToday reported on a disposable plastic sheath that can be used with some endoscopes to prevent exposing patients to potentially contaminated instruments. In DesignNews, Thryft reports on a more sophisticated approach for improving device safety: Materials suppliers and medtech designers are investigating new instruments that are a hybrid of metals and plastics that take advantage of the design freedom afforded by plastics while optimizing the sterilizability of all device components.

"One of the major results of the endoscope sterilization failure case, and others like it, is a major push for device OEMs to go back and design for sterilizability, or even for verifiable sterilizability," writes Thryft, quoting Duane Wand of Solvay Speciality Polymers. This means developing designs for complex multi-part instruments that can be easily taken apart, sterilized and reassembled for inspection, she adds.

In addition to improving patient safety, plastics can also contribute to cost reductions in the manufacture of medical devices. "Injection molding can economically produce millions of identical parts with complex geometries," Mark Yeager, Engineering Manager, Bayer MaterialScience, told Thryft. "For this reason, plastics have already displaced metal in a wide array of applications in which the high cost of metal fabrication is prohibitive."

Metal replacement also enables lightweighting of medical devices, a demand that is driven especially by the home-care market. Devices used by patients need to be rugged but also portable, and engineered materials such as composites or PEEK can satisfy those requirements. However, these materials can be quite costly. "Injection molding parts from plastic can be a cost advantage over metals, if you can get the materials cost down," Andy Pfahnl, Chief Technology Officer at medtech consultancy Devicix, told Thryft.

Go to the DesignNews site to read Thryft's full article.

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