Minimize friction of lubricated laser-microtextured-surfaces by tuning microholes depth

We have investigated the friction properties of lubricated laser microtextured surfaces. The microtexture consists of a square lattice of micro-holes whose diameter, depth and spacing are controlled during the laser texturing process. All surfaces have the same texture area density, but different diameter and depth of the micro-holes. We measure the coefficient of friction on a range of sliding velocities covering the range from the mixed lubrication to the hydrodynamic regime. We find that the depth and diameter of the micro-holes have a huge influence in determining the amount of friction reduction at the interface. Interestingly experiments also show that optimal micro-hole depth values, minimizing the friction in the hydrodynamic regime, are remarkably effective also in the mixed lubrication regime.