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Hydration Friction in Nanoconfinement: From Bulk via Interfacial to Dry Friction
Publikationstyp
Journal Article
Date Issued
2017-10-11
Sprache
English
Journal
Volume
17
Issue
10
Start Page
5969
End Page
5975
Citation
Nano Letters 17 (10): 5969-5975 (2017)
Publisher DOI
Scopus ID
Publisher
American Chemical Society
The viscous properties of nanoscopically confined water are important when hydrated surfaces in close contact are sheared against each other. Numerous experiments have probed the friction between atomically flat hydrated surfaces in the subnanometer separation regime and suggested an increased water viscosity, but the value of the effective viscosity of ultraconfined water, the mechanism of hydration layer friction, and the crossover to the dry friction limit are unclear. We study the shear friction between polar surfaces by extensive nonequilibrium molecular dynamics simulations in the linear-response regime at low shearing velocity, which is the relevant regime for typical biological applications. With decreasing water film thickness we find three consecutive friction regimes: For thick films friction is governed by bulk water viscosity. At separations of about a nanometer the highly viscous interfacial water layers dominate and increase the surface friction, while at the transition to the dry friction limit interfacial slip sets in. Based on our simulation results, we construct a confinement-dependent friction model which accounts for the additive friction contributions from bulklike water, interfacial water layers, and interfacial slip and which is valid for arbitrary water film thickness.
Subjects
Friction | hydration | molecular dynamics simulations | nanoconfinement | viscosity | water
DDC Class
620: Engineering