Determining lubrication properties of hierarchical groove patterns using mesoscale raster-scanning measurements

In this study, we characterized the lubrication properties of two different hierarchical patterns comprising micro -and nanogrooves. The friction coefficient distribution was measured using a convex lens-the friction coefficients were found to periodically undulate along the scan lines with a period equal to the unit pattern. The variation of friction coefficient was more apparent in the case of the Type L pattern with the low boundary bands. For the Type H pattern with the high boundary bands, the undulation in the friction coefficient became clearer at higher sliding speeds, and concurrently, its average friction coefficient decreased with the higher sliding speed. Numerical calculations revealed that oil films formed more easily on Type H patterns than on Type L ones. When pause durations were included in Type H friction tests, the kinetic friction coefficient decreased when the lens slid parallel to the micro/nanogrooves, whereas it was not affected during orthogonal friction.

Automated summary

This study characterizes the lubrication properties of micro- and nanogroove hierarchical patterns. The friction coefficient was found to periodically undulate along the scan lines with a period equal to the unit pattern. The presence of boundary bands affected the variation of friction coefficient, with Type H patterns exhibiting clearer undulation and a decrease in average friction coefficient at higher sliding speeds. Numerical calculations showed that oil films formed more easily on Type H patterns, and the kinetic friction coefficient decreased during parallel sliding but not during orthogonal friction.