Superhydrophilic surface treatment for thin film NiTi vascular applications

A variety of surface treatment methods were evaluated to modify the hydrophilic nature of thin film nitinol (NiTi). It has been suggested that increasing hydrophilicity reduces the prevalence of platelet adhesion and thrombosis in the vascular system. In this study, thin film NiTi was treated with three pretreatments cleaning, buffered oxide etchant (BOE), and BOE/nitric acid (HNO3), followed by one surface treatment. The three surface treatment studied were UV irradiation, thermal treatment, or hydrogen peroxide. Two surface treatments, i.e., thermal at 600 °C for 30 min and 30% hydrogen peroxide treatment for 15 h, produced superhydrophilic surfaces, i.e., wetting angle = 0°. However, the superhydrophilic surface produced by the thermal treatment also embrittled the thin film due to the relative thickness of the oxide grown. Long term studies in air showed that all surface treatments trend toward hydrophobic natures. However, storage of the surface treated thin film NiTi in Deionized (DI) water preserved even the superhydrophilic surfaces indefinitely.