Boundary slip as a result of a prewetting transition

TL;DR

This paper models how a prewetting transition causes boundary slip in fluids, with slip length exhibiting a jump at a specific temperature and a non-monotonous temperature dependence, explaining anomalously low friction phenomena.

Contribution

It introduces a theoretical model linking prewetting transitions to boundary slip, providing a microscopic explanation for large slip lengths observed in experiments.

Findings

Slip length jumps at the prewetting transition temperature.

Temperature dependence of slip length is non-monotonous.

Slip behavior depends on fluid-surface interaction strength.

Abstract

Some fluids exhibit anomalously low friction when flowing against a certain solid wall. To recover the viscosity of a bulk fluid, slip at the wall is usually postulated. On a macroscopic level, a large slip length can be explained as a formation of a film of gas or phase-separated `lubricant' with lower viscosity between the fluid and the solid wall. Here we justify such an assumption in terms of a prewetting transition. In our model the thin-thick film transition together with the viscosity contrast gives rise to large boundary slip. The calculated value of the slip length has a jump at the prewetting transition temperature which depends on the strength of the fluid-surface interaction (contact angle). Furthermore, the temperature dependence of the slip length is non-monotonous.