The effect of wetting on the microhydrodynamics of surfaces lubricated with water and oil

By taking a single asperity contact the hydrodynamic interaction of surfaces with modified wettability was investigated. It was shown that for water as well as for oil the Newtonian friction is valid even for a liquid film thickness in the lower nanometer range, provided that the liquid wets both surfaces. In the case of non-wetting surfaces, the Newtonian friction law breaks down and the hydrodynamic effect is reduced significantly. The results are discussed with respect to their application for microtechnology as well as for macroscopic applications.