TESTING
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When paired with its biobath (shown here), Instron's standard video extensometer enables noncontact load and strain measurements in an environment that simulates
in vivo conditions.
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The importance of a medical device is immeasurable; its limitations are not. Failure of a device or its components is potentially catastrophic and can place a patient in peril. Because medical devices play such vital roles in keeping patients alive and healthy, their durability and characteristics must be proven safe and effective. Testing and inspection of medical devices is the stage that will literally make or break a product. And as time and technology change and progress, so do testing equipment and processes.
Eliminating human error through automation
History has proven time and time again that the human race is fallible. And while society can accept human error as an inherent flaw in the species, medical device testing does not have that luxury.
Unfortunately, testing processes and systems over the years have been vulnerable to human error, which may have contributed to inaccurate records and device failure. Problems associated with manual testing include possibly handwritten or no data, transcription error, faulty connections, and testing to the wrong values, according to Jeffrey St. Onge, chief engineer for the medical division of QuadTech (Maynard, MA, USA), a provider of automated electrical testing solutions.
Because of the dire consequences an error in device testing can have, manufacturers are migrating toward automated testing systems in order to eliminate the human factor. Keeping payroll costs down while increasing volumes is yet another incentive to automate systems, as is streamlining processes. "The automation trend that more progressive and larger manufacturers are [adopting] removes the human factor, applies software, integrates to electronic device history records (DHRs), and supplies electronic data," St. Onge says. "The operator connects once, goes through all the tests once, updates electronic DHRs, creates electronic certificates, and prints them."
The attraction of automated systems is not going unnoticed by suppliers. Crescent Design (San Diego, CA, USA), an engineering firm that provides custom and standard testing systems, offers a variety of automated testing systems aimed at keeping operator costs down and increasing productivity. When connected to the company's smart manifold, its hydraulic burst/leak testing system can conduct tests on 10 parts simultaneously without operator supervision. Test applications include angioplasty balloons and catheters, plastic tubing, valves and luer fittings, cannulae, and IV bags. Likewise, QuadTech has introduced the Sentinel system, a fully automated testing device that controls line voltage to the sample under test while conducting hipot, leakage current, and functional tests.
But while automated testing is gaining steam, the percentage of manufacturers employing automated testing systems in the industry is still relatively small, according to St. Onge. He attributes some resistance to people's fear of change and of abandoning a system or process that has proven successful for the company. Alternatively, start-ups and small businesses may not have the capital to install automated systems. In many of these instances, companies are implementing semiautomated testing. "That term can mean a lot of things," notes Steven Royce, president of Crescent Design. "It could mean it's a simple fixture that holds it for them so they can put it on more easily and more repeatably. It could also mean elimination of that task by a human."
As profits increase, these businesses often adopt fully automated systems over time. Automated systems are expected to become much more universal in the industry within the next several years.
Ensuring accurate results with noncontact systems
Human error is just one of several complications and challenges that arise when testing and inspecting devices and their components. "The medical products industry typically requires a lot of plastics, polymers, rubbers, and soft materials that don't [always] lend themselves to contact methods of measurement and inspection," observes Frank Demski, a sales representative for Mitutoyo (Aurora, IL, USA), a manufacturer of precision measuring instruments and products.
Coordinate measuring machines (CMMs) and other contact equipment have traditionally served as the standard for measurement and inspection. However, the rise of soft materials has spurred the industry to seek other options. In turn, high-speed noncontact camera-based inspection systems are beginning to replace CMMs in many of these medical applications, according to Demski.
"Whereas [noncontact inspection systems] were limited in capability and accuracy even a couple of years ago, they're making great strides very quickly and dominating things that used to be very popular, like CMMs and systems like that," he says. "I would expect that the advances in the near term will be made on that end. Noncontact inspection systems continue to get faster, more accurate, and more flexible to serve a much wider variety of work."
And noncontact systems could serve a wider variety of materials, such as metals, too. Delicate materials such as fine wire and thin film cannot withstand a typical contact extensometer, according to Instron (Norwood, MA, USA), a supplier of testing equipment. Moreover, contact points can create stress concentrations on the part, and the contact force of the extensometer may increase apparent stiffness or distort specimens, thereby yielding inaccurate results, the company says.
In an effort to overcome these drawbacks, Instron has developed noncontacting video extensometers that use high-resolution digital cameras and real-time image processing suited for the testing of metals. Strain measurement is achieved by tracking contrasting gauge marks that are positioned on the material. The company also offers the BioPuls submersible pneumatic side-action grips and temperature-controlled bath with pneumatic lifting and lowering mechanism that can be paired with the standard video extensometer. These accessories enable accurate measurements of load and strain in an environment that simulates the human body, according to the company.
Planning ahead for device testing
Advancements in noncontact measurement and automation are helpful solutions for testing devices quickly and effectively. But if testing was not a consideration in the design stage of a device, these testing advancements may be for naught.
Although the testing phase comes later in the process of ushering a product to market, it should not be an afterthought. In the frenzy to fast-track a product to market, manufacturers often neglect device testing during the design and development stages, according to Royce.
"Don't wait until the product is designed and validated before you go to someone and say, 'please build me a tester,'" he advises. "I can't tell you how many times we've been given a part and if they had just added two little holes so that we could get a hold of it easily and register it properly, life would be wonderful. But they don't, so we often have to go to rather extreme lengths to accommodate testing after the fact when it would have been so simple at the front end."
Royce recommends that manufacturers team up with a company that will be involved with the final testing or assembly early in the design process. "The small expense that [manufacturers] may incur on the front end working on that initial design will pay off big dividends when the final testing needs to be done," he says.
