Viscosity and lubricity of aqueous NaCl solution confined between mica surfaces studied by shear resonance measurement.

We report the viscoelasticity of the thin film of aqueous NaCl solution confined between mica surfaces measured by shear resonance apparatus. The observed shear resonance curves at separations less than ca. 2 nm indicated that the solution exhibits the high lubrication effects under some loads. The effective viscosity (0.1-10 Pa s) obtained for the separations less than 1 nm from a mechanical model was 2-4 orders of magnitude larger than the bulk value. Our study employing a novel shear measurement provided a comprehensive picture for the dynamics of confined water thinner than a few nanometers.