Investigations of plasma-polymerized films as primers for Parylene-C coatings on neural prosthesis materials

• Published in: Thin solid films 1991-07, Vol.202 (1), p.39-50
• Main Author: Yamagishi, Frederick G.
• Format: Article
• Language: English
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/0040-6090(91)90539-A

A need exists to protect neural prosthesis devices from corrosion by biofluids in order to enhance their usable lifetime. Parylene-C is useful and biocompatible polymer coating, but its adhesion to metals used in these devices is not sufficient to achieve the necessary lifetimes. We developed plasma-polymerized hydrocarbon films to act as primer layers for enhancing the adhesion of Parylene-C to metallic surfaces. It was found that the metal surface should be clean and that the wet and dry adhesion of the overcoating is a function of the chemical nature of the surface. Thus, excellent wet and dry adhesion was obtained on clean tantalum and silicon surfaces which had been overcoated with a very thin layer of silicon dioxide. In each case this thin layer was overcoated with plasma-polymerized methane and then Parylene-C. Since the latter two processes are free radical processes, covalent bonds are created to enhance the adhesion. Cleaning procedures and careful reaction conditions are necessary. These are described.