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December, 2016 ElEctronic Mfg SErvicES
Organic Silicone Coatings for Next-Gen Medical Devices
By Jeff Elliott S
ilicon dioxide, or silica, is one of the most abundant minerals on earth. Most commonly found in nature as quartz, it is the major con-
stituent of sand and a primary component in sili- cone and glass. Now, this basic compound is being used in plasma-enhanced chemical vapor deposi- tion (PECVD) techniques as an anti-microbial bar- rier, a primer to promote adhesion between stain- less steel and proprietary coatings, or to create hy- drophobic or hydrophilic surfaces. For many medical device manufacturers, the
application of proprietary coatings and surface treatments can play a significant role not only in new product development, but also when upgrad- ing legacy medical devices under 510(k) guide- lines. As a result, the medical device industry is aggressively investigating and applying plasma- applied coatings to products such as stainless steel guide wires, catheters, stents, and vascular surgi- cal tools. “We are always looking for unique and novel
ways to make our products more robust and be- come the market leader, but to do that we need to bring more technology to our devices. Often, that is going to involve some form of
coating to functionalize the surface,” explains Aaron Baldwin of MicroVention, a company that offers a variety of neuro-interventional products including access products, intraluminal stents, oc- clusion balloons and polymer coils.
“PECVD can take a product to the next level
by addressing surface reaction issues such as bio- compatibility or lubricity. It is a unique and elo- quent way to deposit and enhance coatings be-
(vapor) to a solid state on a substrate. To deposit sil- icon dioxide using PECVD, organic silicones are of- ten required as the feedstock. Within this family, the best known are hexamethyldisiloxane (HMD- SO) and tetramethyldisiloxane (TMDSO). HMDSO, in particular, is an affordable and
flexible reagent that is commercially available in a high-purity, liquid form. The volatile, colorless liq- uid can be plasma-polymerized to create a variety of surface coatings that are safe for medical use. Depending on the composition of oxygen to HMD- SO, the property of the surface can be hydrophobic or hydrophilic. In fact, it is this flexibility that makes HMD-
SO and other siloxanes the ideal choice for PECVD. By adjusting the parameters and other gases added, chemists can tightly control the ma- terial to address a wide range of applications. In the medical device industry, the primary
Organic silicones can be deposited on medical devices, such as catheters, as a surface primer to promote the adhesion of other coatings.
cause it allows you to tailor the surface while re- taining the bulk material’s properties you need,” he adds.
PECVD of Organic Silicones Plasma-enhanced chemical vapor deposition is
a process used to deposit thin films from a gas state
uses of organic silicones fall into the primary cate- gories of protective barriers (antimicrobial, anti- fungal and anti-corrosion) as a primer between stainless steel or exotic metals and proprietary surface coatings, or to modify the surface to be- come hydrophobic or hydrophilic.
Primer Adhesion and Anti-Corrosion When the substrate is metallic, like stainless
steel or other exotic alloys, it can be difficult to ad- Continued on next page
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