Surface Nanostructuring of Ti6Al4 V Surfaces for Parylene‑C Coatings with Ultradurable Adhesion

While Parylene-C is known for its excellent mechanical properties and biocompatibility, its applicability for long-term implants is limited by poor adhesion to many commonly used implant alloys. While the commonly adapted route for adhesion promotion offers significant improvement for dry adhesion, it does not ensure long-term stability in permanent contact with fluids. In this work we investigate different synthesis routes for titanium oxide nanostructures on Ti6Al4 V which serve to physically anchor Parylene to the metal surface. The obtained titanium oxide nanostructures have a range of differing morphologies and dimensions and achieve approximately a 550 larger specific surface than an ideally flat surface. The influence of different nanostructures’ characteristics on the wet-adhesion of Parylene-C was investigated by accelerated aging of Parylene at 80 °C for 72 h in Hank’s balanced salt solution (HBSS) and subsequent blisterlike adhesion testing. The aging procedure caused reference samples with polished surfaces and silane A-174 adhesion promoter to experience an 88% reduction in failure load at which the Parylene film delaminates compared to the unaged samples. Nanostructured samples performed equally well before and after aging, corresponding to an 840% failure load increase compared to the reference surfaces. These findings may allow new applications of Parylene-C for long-term applications in liquid environments, which were previously prohibited because of poor adhesion