The rheology of liquids very near to solid boundaries

Abstract

The experimental evidence for and against the existence of rheological abnormalities in liquids within about 1 μm from a solid boundary is critically reviewed. It is significant that, in those experiments where great care was taken to exclude dust, no anomalous effects were found. Work by the present authors has demonstrated conclusively that the apparent rigidity of thin films of kerosene, which has been reported by previous workers, is due solely to dust particles. It is concluded that rheological abnormalities are now known to extend no further than a few molecular diameters from a solid boundary in pure liquids and, whilst the situation in liquids containing surfactants is still a matter of controversy, there is no sufficient reason yet to believe that rheological abnormalities extend any further in these liquids.