Patterning on different scales to guide lubricants effectivelyTuesday (27.09.2016) 15:15 - 15:30 Part of:
In nature there are numerous examples showing multiscale surface patterns with excellent wetting and friction properties. Inspired by this, periodic line-like structures on different scales were fabricated on stainless steel samples (AlSi-304) by a combination of hot micro-coining and laser surface texturing (LST). A detailed characterization of the resulting surface topography was performed by white light interferometry and scanning electron microscopy. The spreading dynamics of additive-free synthetic polyalphaolefine oil on a polished reference sample are compared to the patterned surfaces. These studies are conducted using a newly developed test rig, which allowed for controlled temperature gradients and a precise recording of the spreading dynamics of lubricants on sample surfaces. It could be demonstrated that the spreading velocity parallel to the structures is higher for all samples with multi-scale surface patterns which can be explained by increased capillary forces and liquid pinning induced by the surface patterning. Furthermore, a decline of the spreading velocity over time for all samples and orientations is clearly visible which can be traced back to a viscosity increase induced by the temperature gradient and a reduced droplet volume. The experimental findings are in good agreement with the Lucas–Washburn equation and established models.