Saltwater Slide

Science  30 Aug 2002:
Vol. 297, Issue 5586, pp. 1441
DOI: 10.1126/science.297.5586.1441e

Previous experiments on thin films of aqueous salt solutions have indicated that the friction increases by several orders of magnitude, as the thickness of the layer approaches molecular dimensions. The implication from these observations was that the water molecules are tightly bound to the ions, and that these clusters are fairly immobile. Working with very clean surfaces, Raviv and Klein (p. 1540) find that the hydrated layers are mobile, and that the maximum viscosity is much lower. The authors believe that an exchange mechanism in which water molecules solvate different ions allows for the high mobility while under compression.


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