From hydrophobic to hydrophilic: Enhancing surface properties of parylene F coatings through oxygen plasma...

Parylene F has emerged as a critical material in interventional surgeries and medical applications, owing to its outstanding biocompatibility, mechanical robustness, and stability in physiological environments. However, its inherent hydrophobicity poses challenges, including increased frictional resistance and potential patient discomfort. To address these limitations, this study introduces an oxygen plasma treatment strategy to enhance the hydrophilicity and biocompatibility of Parylene F coatings. The coatings were deposited on 316 L stainless steel substrates via chemical vapor deposition and subsequently modified using oxygen plasma at power levels ranging from 30 to 80 W. A comprehensive characterization of surface properties was conducted using SEM, AFM, Raman spectroscopy, FTIR, and XPS. Wettability was evaluated through static contact angle measurements, while biocompatibility was assessed via NIH3T3 fibroblast cytotoxicity assays and hemolysis tests. The results revealed that oxygen plasma treatment significantly improved surface hydrophilicity by introducing oxygen-containing functional groups and creating nano structures, reducing the water contact angle to below 20 °. Although a gradual recovery of hydrophobicity was observed due to surface aging, the modified surfaces retained superior wettability compared to untreated controls. Cytotoxicity tests demonstrated cell viability exceeding 90 %, and hemolysis rates remained below 2 %, meeting stringent medical standards. The optimal plasma power for achieving the best hydrophilicity and biocompatibility was identified as 50 W. These findings highlight the effectiveness of oxygen plasma treatment in enhancing the surface properties of Parylene F, making it a promising candidate for interventional medical devices.