Parylene conformal coating boasts a bevy of benefits and properties that make it an appealing choice for a variety of medical device applications. Chief among parylene’s advantages for medical applications, however, is that it meets USP Class VI and ISO 10993 biocompatibility requirements—a characteristic that is essential for many critical medical products and that other types of conformal coating sometimes lack.
But the benefits don’t stop there. Parylene also provides:
- Excellent moisture, chemical, and dielectric barrier properties
- Pinhole-free coating
- Tin whisker mitigation
- Minimal increase in weight and volume
- Dry-film lubricity
- Penetration of crevices and small nooks
- Adhesion to a range of substrate materials
- Thin and truly conformal coating of a substrate
- Sterilization options that include EtO, gamma, autoclave, and E-beam
And in the case of medical implants or medical devices that are inserted into the body, in particular, parylene performs double duty by protecting them from direct exposure to the harsh environment of the human body while protecting the human body from the foreign medical device. We highlight three such types of medical products that profit from parylene’s unique blend of properties.
Catheters, which are inserted into the body for a variety of reasons, reap the benefits of parylene’s proven biocompatibility and barrier properties. However, parylene conformal coating most notably lends a low coefficient of friction that translates into enhanced lubricity to these medical devices. Imparting lubricity nearing that of PTFE, parylene conformal coating of catheters facilitates smooth navigation of the tortuous curves of the human body.
When applied to electronic cardiac-assist devices such as pacemakers and implantable cardioverter-defibrillators (ICDs), parylene conformal coating encapsulates the sensitive medical electronics necessary for the life-critical implants to function. This parylene seal serves to protect the medical devices and their electronics from exposure to the potentially damaging and corrosive effects of bodily fluids, which can compromise performance or even cause medical device failure. Furthermore, the parylene coating creates a barrier between the implant and the body so that the body is not exposed to potentially dangerous materials and chemicals employed in the device. As a dielectric, parylene also forms an electrical barrier between the electronics inside the implants and the electrical signals generated by the surrounding body systems.
Because of the vapor-deposition polymerization process by which it is applied, parylene conformal coating is prized for being completely conformal and yielding a uniform thickness. These advantages are particularly useful in coating stents, which feature complex geometries. In addition, parylene’s lubricious nature aids in stent positioning while its corrosion-resistant properties help to protect the metal-based device from bodily fluids. Parylene has risen to further prominence in this field in recent years by enabling the controlled release of drugs as well as by acting as a bonding agent or tie layer on drug-eluting stents. In this latter capacity, the parylene coating is leveraged because it adheres well to both the bare metal stent and the therapeutic agent.