Formation of periodic nanostructures with femtosecond laser for creation of new functional biomaterials

Pure Titanium (Ti) and Ti alloys are the most used biomaterials. However, they have problem for bioactivity because metals have no biofunction. Therefore, adding new function to Ti and Ti alloys are necessary. One method to add new function is the creation of periodic structures on the biomaterial surfaces, which can control cell spreading. Femtosecond laser is one of the useful tools for creating periodic nanostructures, which can be created on metals and semiconductors by self-organizing in the laser focusing spot. In our previous study, the nanostructures could be formed on the Ti plate by using the femtosecond laser with fundamental wavelength of 775 nm. The periodicities of the nanostructures on the Ti plate was approximately 590 nm, which was shorter than the laser wavelength. Cells tests indicated that cell spreading clearly occurs along the grooves of the nanostructures. However, the influence of the periods of the nanostructure on cell spreading has not yet been investigated. It is expected that the periods can be varied by changing laser parameters, such as pulse widths, laser wavelengths, laser fluences, and number of shots. In this study, the periodic nanostructures are created on the Ti plate surface by using the femtosecond laser with fundamental wavelength of 790 nm. Then, influence of the pulse width and number of shots on the periods is investigated. In the experiments, laser beam is focused and scanned on the Ti plate surfaces. The laser irradiated areas are analysed by using a scanning electron microscope (SEM).