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The rules no longer apply. Materials do more than simply act as the foundation for form and function. Coatings are crossing boundaries to mix with materials rather than just coat them. This is creating an entire new world of possibilities for medical design engineers.

A new tool for designing the smallest medical devices

In their focus on developing products for both short and long-term implantable medical devices, DSM biomedical has created the thinnest fiber ever to be used in the medical market.

DSM’s Dyneema Purity 10 dtex fiber holds this claim. It is the thinnest, high-strength, medical-grade ultra-high-molecular weight polyethylene (UHMWPE) fiber known today. The fiber is four times stronger than polyester and thinner than any other UHMWPE medical fiber on the market. The fiber’s slim property promotes the design of smaller devices, which can be used in support of minimally invasive surgical procedures. The typical results are less discomfort and faster recovery times for patients.

Carola Hansen, director, biomedical polyethylenes, says that production of all very thin medical fibers requires consistent quality and clean fiber material. These two issues are challenges for any fiber to begin with, but the smaller fibers are, the bigger the challenge grows. It required years of research and investment in proprietary technology before DSM launched its first UHMWPE fiber in 2004, Dyneema Purity fiber. Dyneema Purity 10 dtex fiber is the newest addition to the product portfolio. It has been fully validated and is commercially available across global markets.

Materials and Coatings that Go One Step Beyond, Fig. 1

The fiber is available in white for use where a minimal visual profile is preferred. It is also available in blue to offer surgeons better contrast during production of medical devices and during surgical interventions. “It has low elongation and hardly stretches under tension, yet it is also flexible and soft,” Hansen adds. “Of course, it is biocompatible and is compliant with ISO 10993 standards. Our first clinical applications focus on cardiovascular sutures, used in minimal invasive interventions. This is a growing area and Dyneema Purity 10 dtex fiber allows us to expand further into the field.”

Tough material ensures device and patient safety

Eastman Chemical Company is a global specialty chemical company that works with customers to deliver innovative products and solutions. In the medical area, one key innovation is Eastman Tritan copolyester. This is a very rigid, hard plastic that is typically used in device housings, connectors, blood oxygenators, or other parts that need a very durable material that won’t crack or break if dropped (or else degrade when exposed to chemicals or sterilization).

Materials and Coatings that Go One Step Beyond, Fig. 2

Emmett O’Brien, Ph.D., Eastman’s principal applications engineer, says that a number of things make this product unique: “In the medical and hospital environment, there is a significant need for plastics to be very chemically resistant. In addition, materials also need to have a specific set of properties to ensure the safety of the device and patient. Tritan does all of this.”

Tritan has the four basic properties needed for the medical environment: It’s clear, which allows health care professionals to help ensure the device is working properly. It’s also an extremely tough material, which is critical for its applications. Additionally, the properties of the material are not affected when exposed to any type of hospital aggressive disinfectants, cleaners, pharmaceuticals, or oncology drugs.

“Also when, gamma sterilization is used on other plastics, they turn very yellow and their mechanical properties can be affected,” says O’Brien. “With Tritan, there is such minimal color shift, you can’t tell the difference before and after sterilization.”

Materials and Coatings that Go One Step Beyond, Fig. 3

In February, Eastman introduced the newest grade, Tritan copolyester MXF121, which offers an opaque material option. It is specifically designed to have a flammability rating necessary for certain electronics required for portable battery housings. It has the toughness of all Tritan materials but it has even better chemical resistance. Hand-held and other medical electronic device housings demand vigilance to prevent hospital-acquired infections (HAIs). Many products used to combat HAIs are chemically incompatible with thermoplastics such as PC and PC/ABS, potentially resulting in compromised performance due to cracking or crazing. MXF121 provides excellent chemical resistance against these cleansers.

Materials and Coatings that Go One Step Beyond, Fig. 4

O’Brien says that currently, the MXF121 is Eastman’s focus, and the company is working with customers to develop more applications. “We are also working on a grade that will reduce blood clotting—anti-thrombosis. Another will reduce static so powder type medications don’t stick to the plastic itself. We are also working on even better plastic materials that will withstand autoclave sterilization.”

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