Anisotropic Spreading Behavior of PAO Oil on Laser-Patterned Stainless Steel Surfaces

Periodic line-like structures with different periodicities (5 and 10 mu m) were fabricated by laser interference patterning on stainless steel samples. A detailed characterization of the resulting surface topography and its homogeneity (analyzed by power spectral density) was performed by white light interferometry. The resulting anisotropic spreading behavior of an oil droplet, a Poly-(alpha)-olefin with a relatively small kinematic viscosity, was investigated on the patterned surfaces. The droplet motion was recorded by a digital light microscope, with the length and width measured at different intervals, revealing droplet distortion. From this study, it can be concluded that the periodicity and aspect ratio, are the most influencing factors with regard to the spreading behavior. Surface patterns with smaller periodicities and larger aspect ratios lead to a larger droplet distortion, whereas the homogeneity of the pattern plays a minor role.