Medical Coating Specialists
Specialty Coating Systems is the leading international source for effective medical coating answers - from application engineering and equipment design to high performance materials and responsive coating services.
Parylene is a vacuum-deposited polymer film that has been used to protect and treat substrates and component surfaces for more than 30 years. This thin, transparent coating provides unique benefits for medical coating applications because it is very thin, inert, biostable and biocompatible.
Parylene can meet a wide range of medical coating applications, including electronic pressure sensors and transducers, cardiac assist devices, prosthetic components, electronic circuits, drug packages, laboratory pipette trays, catheters, mandrels, needles and cannulae.
Notable properties of Parylene medical coating include pinhole-free coverage, freedom from solvents and catalysts, high dielectric strength, useful moisture and gas barrier performance in very thin layers, and excellent dry film lubricant characteristics.
This medical coating is a high molecular weight, linear, crystalline polymer with an all carbon backbone. It is available in four specialized molecular forms, each with its own particular properties. The Parylenes are quite hydrophobic due to the absence of polar entities in their essential makeup. This characteristic, coupled with substantial crystallinity, makes the Parylenes quite stable and resistant to chemical attack.
This film can be applied to medical surfaces in infinitely-controllable thicknesses from less than 100 nanometers to hundreds of micrometers. Transparent Parylene conforms precisely to complex surface geometry without bridging or pooling.
Parylene has the ability to modify substrates and thereby satisfy one or more medical performance requirements. For example, Parylene can render coated surfaces biocompatible. This material is essentially unaffected by corrosive body tissues and fluids, as well as various solvents and chemicals that might be encountered in use. The film has been evaluated in blood compatibility tests and found to be significantly superior to alternate materials such as poly(hydroxyethyl methacrylate), and various fluorinated polymers. Coating performance is enhanced by the pinhole-free nature of this thin film, which forms a complete encapsulating barrier over coated objects.
There are no specific FDA regulations pertaining to the physiological compatibility of any Parylene polymer or precursor. However, SCS maintains a Master File with the FDA that is a compilation of available information in this area. This file is intended to assist the FDA in determining the safety of Parylene for specific applications.
Dielectric protection is another Parylene surface modification feature. The film has an electrical insulation value of approximately 5000 volts per mil of thickness, and it can be applied to isolate electrical conductors - either selectively or overall - without changing dimensions appreciably.
With its low static and dynamic coefficients of friction, Parylene adds useful surface lubricity or slipperiness to medical objects. This function is particularly useful for items such as catheters or other objects that must move against opposing surfaces.
A thin coating of Parylene is able to immobilize micro-particles on surfaces that are prone to flaking, and it also seals porous substrates so as to restrict entrapment of contaminants. The coating also mechanically stabilizes delicate structures, and thereby supplements physical strength without adding significant mass or changing structural profiles.
Finally, Parylene film can be used to create an intimal surface that promotes tissue growth in a manner that is useful for certain surgical applications.
These surface modification functions apply to both short-term use (for example, surgical tools and treatment components) and long-term use (ie., medical implants).
The effective use of Parylene requires that surfaces be absolutely clean, with no residual chemicals, oils, fingerprints, dust or other contaminants that could interfere with bonding between the coating and substrate. Substrate cleanliness can be confirmed by immersing parts in an instrumented final rinse tank for ionograph measurement.
When Parylene is to be selectively applied, cleaned and prepared substrates must be masked to restrict coating to desired areas only. Various materials can be used for masking, including tapes, elastomer sealants, and specially designed fixtures that also hold substrates in the coating chamber.
Very small components that are to be completely coated can be treated in a manner that exposes all surfaces to the monomer. No fixturing is required for this proprietary process, parts are evenly coated without fixture marks, and the system makes extremely efficient use of the Parylene raw material.
Parylene is a sophisticated, high performance solution to certain medical coating requirements, and provides results that cannot be achieved with alternate materials and processes. Since the cure cycle is automatic with Parylene and occurs before deposition, substrates are not subjected to cure forces, solvents or elevated temperatures, and no testing is required to confirm that full cure has occurred.