We will discuss the relation between microscopic contact water structure, and dynamics and hydrodynamic boundary conditions, as observed from equilibrium and non-equilibrium MD simulations. Experimental observations suggest that because hydrophobic surfaces repel water, they sustain hydrodynamic slip while hydrophilic surfaces cannot. Our results suggest instead that water can slip on both hydrophobic and hydrophilic surfaces, and that the structure and dynamics of water molecules within the first hydration layer near the surfaces are responsible for this observation. When contact water molecules are able to slide from one preferential adsorption site to another, without necessarily leaving the hydration layer, hydrodynamic slip can be observed. Towards developing macroscopic quantities to discriminate between surfaces that can or cannot sustain water hydrodynamic slip, we found that contact angle hysteresis, not equilibrium contact angle, provides excellent correlation with slip/no slip. Hydrodynamic slip is observed on surfaces where no contact angle hysteresis is detected.

Water hydrodynamic slip: Molecular and macroscopic signatures

243rd National Meeting (2012)

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