| The myriad uses of polymers in medical devices are both well-established and diverse, from compliant materials used in facial implants to tough bearing surfaces for total joint replacements. The surface mechanical properties of the materials used in medical devices are of paramount importance, as it is at the surface where most interactions take place, either against other synthetic biomaterials or natural tissues. Frequently, only static mechanical properties are measured for these materials, even though most medical devices are expected to undergo dynamic and/or cyclic loading in vivo. Additionally, the characterization of surface coatings and treatments can not be evaluated through conventional mechanical testing. Nano-scale dynamic mechanical analysis (nano-DMA) provides an ideal tool to evaluate surface mechanical properties of biomedical polymers, and is sensitive enough to detect changes due to gas plasma treatments which are expected to modify only the outer micron of a polymer component. In this presentation, validation of nano-DMA will be discussed for various polyethylenes. Changes to microstructural variables such as crosslinking and crystallinity through conventional techniques were investigated and then compared to changes in the surface viscoelastic properties induced by gas plasma surface treatments.;Another aspect of this work was an assessment of the FDA medical device approval process, using a case study of Total Hip Replacements. Mechanisms to improve FDA evaluation times in the face of rapidly emerging medical technologies will be weighed against the need to fully establish the safety and efficacy of new medical devices. |
