Tasked with helping human bodies fight off disease and illness, the medical device market is booming.
Research and development (R&D) teams in the medical device industry have been developing groundbreaking products to help people fight off disease and illness and live longer lives. Able to mimic and support organs and other bodily systems, medical implants are revolutionizing the future of health care.
The human body is programmed to defend itself against all foreign materials, including medical implants made of metal. Medical devices, therefore, must be made out of biocompatible alloys that are designed to withstand the harsh environment of the body. Part of the manufacturing processes in these cases must include the passivation of the biocompatible material to ensure the device’s surface is inert or non-reactive when implanted in the body.
Passivation refers to a material becoming “passive,” in relation to environmental factors such as air and water, including fluids within the human body. In the case of the nickel-titanium shape memory alloy, Nitinol, the passivation of the material helps prevent corrosion as well as aids biocompatibility. For example, the passivation of Nitinol depletes its surface of nickel, a metal that can cause severe allergic reactions in the human body.
Testing the Passivation Layer with ESCA
Testing medical devices for the thickness and composition of the passivation layer is a necessary step in the quality assurance process. This will ensure that there is minimal risk of a patient suffering an allergic reaction once the device is implanted. There are some unique materials testing methods which R&D teams can rely on during different steps of production.
Since the passivation layers of Nitinol are usually quite thin (on the order of ten to two hundred Angstroms), Electron Spectroscopy for Chemical Analysis, or ESCA is one of the few surface analysis techniques capable of providing a chemical analysis of the layer. Also called x-ray photoelectron spectroscopy or XSP, ESCA has sampling depths of approximately thirty Angstroms and can provide information about the chemical composition as well as thickness of the passivation layer.
The chemical figures of merit used to evaluate passivated stainless steel are the chromium-to-iron and the chromium oxide to iron oxide ratios. Both of these ratios are measurable using ESCA analysis.
Medical Implant Quality Control with ESCA
Nitinol will usually passivate by forming a titanium dioxide layer on the surface. To use Nitinol in medical devices, ESCA is useful for evaluating the passivated surface for the presence or absence of nickel within the passivation layer. This might be useful for analytical chemists immediately after Nitinol has been processed for passivation as well as when a prototype implant is ready for testing.
ESCA analysis, conducted by companies like Innovatech Labs, is an essential part of quality assurance for medical devices and can keep your company rising with the tide of the medical device industry.
Innovatech Labs offers a wide range of analytical services beyond surface analysis techniques like ESCA. To learn about more materials analysis cases than how to analyze passivation layers, see if you can guess which materials characterization technique is used for the cases in this Innovatech Labs blog.