The understanding and ability to manipulate fluids at the nanoscale is a matter of continuously growing scientific and technological interest. Fluid flow in nano-confined geometries is relevant for biology, polymer science and geophysics. The applications range from gene sequencing1 to protein segregation, cell sorting, bio and chemical sensors, nanotribology and diffusion through porous media. Here, we present experiments which show how the boundary viscosity of water strongly depends on the wetting properties of the confining surfaces. This dependence is fully explained by considering water slippage at the stationary solid surface. The boundary viscosity as a function of the gap size for six surfaces with different wettabilities is fitted with a modified form of the Newtonian definition of viscosity, taking fluid slip into consideration. This simple relationship can explain the interfacial viscosity measurements and allows the extraction of a �slip parameter� for each investigated surface. This slip parameter is found to increase with the hydrophobicity of the solid surface as expected from previous work, bringing further evidence of the relationship between boundary viscosity and slip.

Water nanohydrodynamics: The interplay between boundary viscosity, slip, and wettability

244th National Meeting (2012)

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