Rubber Journal Asia Silicones
Key factors for choosing silicone solutions in medical device lubrication This article is by Brian Reilly, Business
Biocompatible silicone lubricant In working with various medical devices, such as needles, syringes, trocars, cannulas, guidewires, catheters and valves, medical device designers must account for friction in the form of insertion, drag and break-loose forces. It is for this reason that biocompatible silicone lubricant can significantly reduce friction at interfaces between components and between components and human tissue. Silicone has a long and proven history of use with medical devices. When choosing a lubricious silicone for an application or a specific device, it’s important to consider several key factors to ensure the lubricant properties deliver the expected result for both the device manufacturing process and the end use.
Development Director – Biomaterials NuSil – part of Avantor Carpinteria, CA.
here are no lagging moments for the medical devices market worldwide, as demand is growing, against the backdrop of expanding healthcare expenditure as a result of universal healthcare reforms; as well as technology advancements; and ageing population and chronic diseases. The market for global medical devices is expected to cross nearly US$410 billion by 2023, at a CAGR of 4.5% from this year to 2023, as forecast by Lucintel. In keeping with the uptrend, access to safe medical devices is ensured by regulatory agencies. The US Food and Drug Administration (FDA) has been keeping a watchful eye on how products classified as medical devices perform and how safe products are for consumer use.
Different lubricants for different substrates A main consideration is to understand the nature of the various substrates that need to be lubricated and identify why the materials and surfaces require different types of silicone lubricants. Medical devices can incorporate a variety of substrates, including silicone, metal, glass and plastics. Each material has different characteristics that can pose unique lubrication requirements. Silicone substrate The surfaces of cured silicone elastomers often exhibit a high coefficient of friction (COF). These surfaces can be tacky, causing problems when molded or extruded parts must move or slide. Silicone elastomers also tend to block, meaning they stick to each other due to chemical affinity. Blocking is particularly evident in slit valves, where the two sides of the silicone part touch each other and “heal” or close the slit. Considerations for silicone parts: • Surface interaction factors: Consider a lubricant with a low chemical affinity to the elastomer For moulded silicone parts, it is important to account for the difference in chemistries between the part and the lubricant itself. Otherwise, the lubricant may diffuse into a chemically similar material, and the moulded component will swell. If this occurs, the fluid is depleted from the surface, which will reduce or eliminate the lubricating effect. Most silicone components are produced using a dimethyl silicone elastomer. Choosing a fluorosilicone lubricant, which has minimal chemical affinity to the dimethyl silicone, will result in minimal diffusion into the substrate.
Device designers should be sure to consider high-purity, medicalgrade silicone lubricant products supported by Master Files with US FDA and international authorities, which include biological tests conducted on each product
FDA describes medical devices as ranging from “common medical supplies (bandages, hospital gowns) to complex instruments that help save and sustain life (heart valves, artificial pancreas); and tools that aid in the detection of disease (MRIs, in vitro diagnostics) and digital technology that is driving a revolution in health care (medical apps, surgical planning tools, closed loop drug delivery devices)”.
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