Functional surfaces featuring periodic structures can 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, patterns with varying spatial periods (gradual periodic structures) can result also on anisotropic functionalities which has been so far not done using DLIP.

In this study, a two-beam DLIP configuration is used for manufacturing gradient surface structures on mirror-polished stainless steel samples. The spatial period of produced gradient line-like pattern is continuously raised from 1.99 ± 0.03 µm to 4.70 ± 0.02 µm by adjusting the interference angle between the two coherent beams. This was performed by adjusting continuously the moving prism in used setup throughout the entire process. The gradient structures are produced in areas up to 5×5 mm². The effect of the different process parameters on the quality of the structures is discussed. Furthermore, multi-pulse strategies have been evaluated in order to improve the quality of the gradient surfaces. The produced topographies are characterized by confocal and scanning electron microscopy methods.