Femtosecond Laser-Induced Hydrophobic Surface of NiTi Shape Memory Alloy and its Blood Compatibility

The study of nickel-titanium shape memory alloy (NiTi SMA) surface wettability is important to improve the blood compatibility of medical implant materials. Herein, a femtosecond laser with a wavelength of 1030 nm is used to process the hydrophobic surface of NiTi SMA. A scanning electron microscope, an X-ray photoelectron spectrometer, a surface profiler, and a contact angle meter are used to measure the microstructure, the chemical composition, the surface roughness, and the surface contact angle of NiTi SMA. The influence of the laser fluence on the NiTi SMA surface wettability is analyzed using the Wenzel-Cassie composite model. The results show that as the laser fluence increases, the surface roughness gradually increases and then fluctuates. Moreover, a rapid increase followed by a gradual rise is observed in the surface contact angle. The blood compatibility of NiTi SMA surface increases with the increase in the surface contact angle. Specifically, the superhydrophobic surface with high contact angle and low rolling angle can significantly improve hemolysis and coagulation while reducing platelet adhesion and deformation. The study of the superhydrophobic microstructure of NiTi SMA surface will provide a new approach for improving the blood compatibility of medical implant materials.