Parylene coating is popular in the healthcare industry due to its excellent biocompatibility, chemical barrier properties, and dielectric performance. It has gradually become the preferred material for surface coating of biomedical devices. This article introduces the application of Parylene coating in the healthcare industry.
Meaning of Parylene Coating
Parylene is a common term for a series of unique polymers, namely poly-para-xylylene. It is a completely linear, highly crystalline material.
Parylene coating is prepared using a unique vacuum vapor deposition process, where active small molecules “grow” into a completely conformal polymer thin film coating on the substrate surface.
It can be applied to surfaces of various shapes, including sharp edges, cracks, and inner surfaces. This 0.1-100 micron thin film coating, prepared at room temperature, is uniform in thickness, dense and pinhole-free, transparent and stress-free, additive-free, non-damaging to workpieces, with excellent electrical insulation and protection properties. It is an excellent moisture-proof, mold-proof, corrosion-resistant, and salt spray-resistant coating material.
Why Is Parylene Coating Widely Used In The Healthcare Industry?
| Biocompatibility:
The US FDA has proven that the parylene coating is biocompatible. It meets the US Pharmacopoeia Class VI standard for biomedical materials and the ISO-10993 biological experiment requirements. It is considered a biomedical material that can be implanted in the body for long-term use.
| Applicability: Some medical devices have internal electronic components that need protection (implanted or external). Due to the small size of these electronic components, they are affected by uneven gaps and other factors, making it impossible to use traditional protective coatings. Parylene coating using the vapor deposition method can effectively solve these problems.
| Chemical stability: Polypara-xylylene has excellent chemical stability and can resist corrosion from various corrosive gases and liquids, such as body fluids. A 1um Parylene coating has better alcohol resistance than a 15um silicone oil coating. Its function is not affected by radiation sterilization and oxidation sterilization.
| Thermal stability: Parylene has good thermal stability, making it suitable for medical equipment that requires high-pressure sterilization and can be reused. Parylene coating has good mechanical strength and adhesion, allowing the coating to be used for a long time.
| Insulation and dielectric properties:
Only a very thin layer of Parylene coating is required to provide effective corrosion protection for sensitive electronic components. Moreover, due to its good dielectric properties, it does not affect the normal operation of electronic components.
Applications of Parylene Coating in The Healthcare Industry
Implantable Medical Devices
Parylene coating is often used for surface treatment of implantable medical devices such as pacemakers, artificial joints, and vascular stents due to its excellent biocompatibility and long-term stability. It can effectively protect devices from corrosion in the internal environment while reducing friction between the device and surrounding tissues, improving patient comfort.
| Cardiac assist devices: Parylene coating can prevent corrosion of precision electronic circuits in pacemakers and defibrillators from biological fluids, and can also be used to protect the metal casings of devices.
| Medical stents:
Parylene protects stents by providing good lubricity and effectively preventing biological fluid penetration.
Catheters And Catheter Sheaths
Parylene coating can significantly reduce the surface friction coefficient of catheters and catheter sheaths, making these devices smoother during insertion and removal, and reducing patient pain and trauma. In addition, it can effectively prevent bacteria and other microorganisms from adhering to the device’s surface, reducing the risk of infection.
| Cannulas:
These are precision devices used for abdominal surgery. Conductive metal shaft cannulas insulated with Parylene deposition can guide RF energy to accurate areas at the tip.
| Urinary catheters: Molded devices such as urinary catheters protected by Parylene deposition can provide good lubricity and prevent biological fluid corrosion.
Sensors And Electronic Devices
Parylene coating has good electrical insulation properties and can protect precision electronic components in medical electronic devices from corrosion by body fluids and electrolytes. This makes it an ideal protective material for sensors and circuit boards in medical electronic devices such as electrocardiographs and electroencephalography.
| Pressure sensors: Sensitive electronic devices such as blood pressure sensors only need a small amount of Parylene deposition for sufficient insulation, and the small amount of protective coating does not significantly alter the operation of these devices.
| Ultrasonic transducers:
Microsensors used for observing blood vessel walls can avoid corrosion and insulation breakdown after Parylene deposition.
| Electronic circuits: Electronic circuits on complex instrument surfaces can be protected from water and chemical corrosion and provide good dielectric properties by Parylene coating.
Medical Accessories
Parylene coating can also be used for surface treatment of various medical accessories, such as bone pins, probes, needles, sutures, etc. These accessories need to have good biocompatibility and corrosion resistance during use to ensure patient safety and comfort.
| Bone pins: Parylene protects bone pins and surgical instruments from corrosion and provides lubricity.
| Needles: Parylene deposition on the outer and inner surfaces of needles seals microscopic pores in the metal and forms a smooth, pore-free surface. This reduces the possibility of contaminant adhesion. The permeability of Parylene N makes it very soluble and able to penetrate the inner surface to form a protective layer.
| Brain probes: Parylene can not only make the probe surface smooth but also allow selective insulation.
Pharmaceutical Containers
Whether the application requires barrier properties or dry film lubricity, Parylene coating can benefit pre-filled syringes and pharmaceutical containers. Parylene coating applied at micron-level thickness can prevent leachables and extractables when the substrate contacts drugs. Moreover, due to the similar static and dynamic friction coefficients of the inert Parylene coating, it can eliminate the starting force when using the container.
| Medical bottle stoppers: Parylene coating can be used for the coating treatment of medical bottle stoppers. This coating can block direct contact between the stopper and the drug, preventing drug contamination or degradation. Compared to traditional materials such as butyl rubber stoppers, Parylene coating can improve drug stability and safety.
Medical Textiles
Parylene coating can be used for the treatment of medical textiles such as surgical gowns. Through coating treatment, these textiles can obtain better water resistance and breathability while maintaining their softness and comfort. In addition, Parylene coating can also improve the antibacterial properties of textiles, reducing the risk of infection.
Supplementary Knowledge: Parylene Coating & Gold Coating
Parylene coating and gold coating share the common feature of excellent biocompatibility, which makes both coatings applicable in the healthcare field. However, they each have different advantages, and the appropriate coating should be chosen based on specific performance requirements and cost considerations.
Advantages of Parylene Coating Compared to Gold Coating
| Better chemical stability: This material has good resistance to most chemicals, making it perform excellently in various medical environments and can resist drug and body fluid corrosion.
| Uniform and thin coating: Parylene’s vapor deposition technology can provide a very uniform and thin coating, suitable for small and complex-shaped medical devices such as heart stents.
Advantages of Gold Coating Compared to Parylene Coating
| Better conductivity: Gold coating has excellent conductivity, suitable for medical equipment that requires electrical signal transmission.
| Better corrosion resistance: Gold has strong corrosion resistance and will not oxidize or corrode in biological environments, maintaining long-term stability.
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