Why Parylene Is Still a Go-To Medical Device Coating

Include parylene with the list of medical device materials that have been around for decades, in this case providing a reliable protective coating for devices.

Part of the reason may have to do with how difficult it is to get new types of materials approved with the FDA. But Specialty Coating Systems officials are quick to point out that parylene has plenty of benefits going for it.

Here's what Carla R. Gillespie, a marketing communications manager at Indianapolis-based SPC, had to say about parylene:

MPMN: Describe a little bit about what parylene is? How long has it been used to coat medical devices? How long has Specialty Coating Systems used it?

Gillespie: Parylene conformal coatings are ultra-thin, pinhole-free polymer coatings that provide a number of high-value surface treatment properties. SCS is the direct descendent of the company that originally commercialized parylene over 40 years ago and the coating has protected medical devices nearly all of those years.

MPMN: What are the advantages of parylene? Is it being used more to coat medical devices, and why?

Gillespie: Parylene coatings are biocompatible and biostable, and offer excellent moisture, chemical, and dielectric barrier protection, thermal and UV stability, and have a low coefficient of friction for applications where lubricity is important. Parylene has long been beneficial in medical applications, but as medical devices become smaller and more compact, parylene certainly finds increasing value due to its molecular level deposition. ... Parylene coatings protect a wide array of devices and components, including stents, cardiac assist devices, electrosurgical tools, cochlear and ocular implants, mandrels, and molds, catheters, elastomeric seals, needles and probes, neurostimulation devices, medical electronics, and more.

MPMN: What technical challenges had to be overcome in order for parylene to work for medical devices?

Gillespie: One of the first considerations in the medical industry is whether or not a material is biocompatible and biostable. Parylene coatings are inherently both. SCS Parylenes N, C and Parylene HT have been tested according to the Biological Evaluation requirements of ISO 10993. Further, the biocompatibility and biostability of SCS Parylenes have been demonstrated in a wide range of medical coating applications over the past four decades.

An additional technical challenge arises in the area of coating adhesion. Factors such as surface contamination, presence of oxide layers, and low surface energy substrates can lead to poor adhesion and the reduction in the effectiveness of coatings used in these devices. Optimal adhesion of parylene to a wide variety of substrates is commonly achieved by a treatment with A-174 silane prior to parylene coating. To address difficult metallic and polymeric substrates, newer adhesion technologies are available. ...

MPMN: Any drawbacks around parylene? What should a medical device designer consider when deciding whether to use parylene?

Gillespie: Parylene coating is applied as a vapor in a vacuum deposition process. ... Parylene coating service providers offer the most flexibility in terms of coating high production volumes in a timely and cost-effective manner. However, like all applications are not the same, coating service providers are not all the same. For medical customers, it is important to look for a partner who can not only help achieve the desired results via experienced applications engineering support, but also one who can meet your strict quality requirements and support your FDA submissions with biocompatibility test data. 

Chris Newmarker is senior editor of MPMN and Qmed. Follow him on Twitter at @newmarker.