Generating Nanodot Structures on Stainless-Steel Surfaces by Cross Scanning of a Picosecond Pulsed Laser

Ultrashort pulsed laser-induced periodic surface structures (LIPSS) can be generated on different kinds of materials, which are widely utilized for modifying surface properties such as wettability, adhesion, and tribological, as well as optical performances. Previous studies have focused mainly on one-dimensional LIPSS (i.e., line structure) generation. In this study, a picosecond pulsed laser was used to irradiate stainless-steel surfaces for generating two-dimensional LIPSS, namely nanodot structures, by cross-scanning the laser beam for a different number of times. The obtained nanodot structures were found to be super hydrophilic just after laser irradiation, but turned to be hydrophobic after exposure in air for a few days. By cross-scanning the laser beam for the same number of times, local LIPSS rewriting was realized. This study showed the possibility of improving the homogeneity of the surface properties of steel materials through laser-induced nanodot structuring.