Effects of tuned surface wettability on oil film formation in a hydrodynamically lubricated contact under limited lubricant supply was explored in this study. Utilizing a slider-on-disc lubricating film test rig, oil film thickness was measured for three surface wettability configurations: original disc surface and original slider side surface (OD & OS), AF coated disc surface and original slider side surface (AFD & OS), and AF coated disc surface and AF coated slider side surface (AFD & AFS). The results indicate that the AFD & AFS combination maintains the largest oil film thickness. This enhanced performance is owing to the oil’s non-wetting behavior on the AFD & AFS surfaces, particularly the discontinuous oil droplet/strip by dewetting, which promote more lubricant supply at the slider inlet. Moreover, the oil accumulates at the inlet in the form of convex reservoir so that positive Laplace pressure is generated, which effectively bears part of the load and the film thickness increases. 

Effective oil replenishment to the lubrication track of a running bearing is crucial to its sustainable operation. Reliable practical solutions are rare despite numerous theoretical studies were conducted in the last few decades. This paper proposes the use of surface effect, wettability gradient, to achieve the goal. This method is simple and can be nicely implemented using femtosecond laser ablation. A periodic comb-tooth-shaped pattern with anisotropic wetting capability is devised and its effect on the anisotropic spreading behaviour of an oil droplet is studied. Results show that the comb-tooth-shaped pattern enables the rearrangement of oil distribution, thereby escalating oil replenishment to the lubrication track. The effect is due to the unbalanced interfacial force created by the surface pattern. The influence of the shape and the pitch of teeth, which are the two governing factors, on oil transport is also reported. The effects of the newly devised surface pattern on lubrication are experimentally evaluated under the conditions of limited lubricant supply. These results are promising, demonstrating the reduction in bearing friction and the increase in lubricating film thickness.