Laser-induced wettability gradient surface on NiTi alloy for improved hemocompatibility and flow resistance

Blood contacting materials with anti-thrombotic surfaces are highly demanded in clinics. Despite considerable research on surface modifications, limited progress has been made on effective prevention of thrombosis for artificial implants such as mechanical valve prosthesis. Herein, wettability gradient surface, which can ideally exhibit good hemocompatibility and low flow resistance, was developed for potential reduction of thrombosis. The wettability gradient surface on a model substrate of nickel-titanium (NiTi) alloy was prepared via a simple and economic method that combined laser microfabrication and surface stearic acid self-assembly approach. Scanning electron microscopy (SEM) observation confirmed that the wettability gradient surface was composed of a smooth NiTi region and three porous regions with different pore sizes and distances. Contact angle measurement revealed that, together with a low surface energy layer, the structural topography gradient could create a wettability gradient surface on NiTi alloy which could drive droplet motion. When compared with bare NiTi, such wettability gradient surface exhibited better anti-adhesion property, which was beneficial to the hemocompatibility and thus showing a lower hemolysis rate. Additionally, the wettability gradient surface also showed much lower flow resistance than bare NiTi. These results demonstrate that the developed wettability gradient surface may be used to reduce thrombosis.