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From hydration repulsion to dry adhesion between asymmetric hydrophilic and hydrophobic surfaces

Matej Kanduč and Roland R. Netz – 2016

Using all-atom molecular dynamics (MD) simulations at constant water chemical potential in combination with basic theoretical arguments, we study hydration-induced interactions between two overall charge-neutral yet polar planar surfaces with different wetting properties. Whether the water film between the two surfaces becomes unstable below a threshold separation and cavitation gives rise to long-range attraction, depends on the sum of the two individual surface contact angles. Consequently, cavitation-induced attraction also occurs for a mildly hydrophilic surface interacting with a very hydrophobic surface. If both surfaces are very hydrophilic, hydration repulsion dominates at small separations and direct attractive force contribution can-if strong enough-give rise to wet adhesion in this case. In between the regimes of cavitation-induced attraction and hydration repulsion we find a narrow range of contact angle combinations where the surfaces adhere at contact in the absence of cavitation. This dry adhesion regime is driven by direct surface-surface interactions. We derive simple laws for the cavitation transition as well as for the transition between hydration repulsion and dry adhesion, which favorably compare with simulation results in a generic adhesion state diagram as a function of the two surface contact angles.

Titel
From hydration repulsion to dry adhesion between asymmetric hydrophilic and hydrophobic surfaces
Verfasser
Matej Kanduč and Roland R. Netz
Datum
2016
Kennung
10.1073/pnas.1504919112
Zitierweise
Proc. Natl. Acad. Sci. USA, 2016, 112(40), 12338–12343
Art
Text
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