Surface wettability pattern and shape gradient co-induced oil droplet directional transport for enhancement of lubrication performance

Thermocapillary migration in lubrication systems is a phenomenon in which the lubricant migrates via the interfacial tension difference caused by the nonuniform temperature generated by the wear behavior, which leads to lubricant starvation and results in severe damage. This paper proposes a novel method to eliminate the thermocapillary migration phenomenon, in which we successfully fabricate a surface that combines a shape gradient and wettability pattern on 316 L stainless steel, and the results prove that the prepared surface can not only effectively obstruct liquid paraffin droplet migration but also directionally transport liquid paraffin to the center of the wear track under the thermocapillary migration effect. The results of the wear tests further demonstrated that only the surface combination of a shape gradient and wettability pattern can achieve a decrease in the friction coefficient by means of external lubricant feeding in the state of lubricant starvation, which provides a strategy for improving and developing new types of lubrication enhancement for mitigating starvation lubrication.