Functional surfaces featuring periodic structures cab be manufactured by Direct Laser Interference Patterning (DLIP) for many technical applications. In general, these patterns consist of repetitive surface structures with a fixed spatial period that ranges from the sub-micrometer to the micrometer range. However, repetitive patterns with varying spatial periods (gradual periodic structures) can result on anisotropic functionalities, and have not been intensity investigated.

In this work, a two-beam DLIP configuration is used for manufacturing gradual surface structures on stainless steel. The produced patterns differ from ordinary single-scaled structures since the spatial period has a continuous variation depending on the spatial location. By controlling the interference angle between the laser beams, the spatial period of the structures changed in range from 2 to 5 μm. This variation was produced along macroscopic lengths varying from 1 to 5 mm. The effect on the laser fluence of the structure depth of the structures is also discussed. The produced topographies are characterized by confocal and scanning electron microcopy methods.