Liquid–Solid Nanofriction and Interfacial Wetting

Abstract

Using atomic force microscopy, the nanofriction coefficient was measured systematically for a series of liquids on planar graphite, silica and mica surfaces. This allows us to explore the quantitative interplay between nanofriction at liquid-solid interfaces and interfacial wetting. A corresponding states theory analysis shows that the nanofriction coefficient, μ = dF(F)/dF(N), where FF is the friction force and FN is the normal force, is a function of three dimensionless parameters that reflect the intermolecular forces involved and the structure of the solid substrate. Of these, we show that one parameter in particular, β = ρ(s)Δ(s)σ(ls)(2), where ρ(s) is the atomic density of the solid, Δ(s) is the spacing between layers of solid atoms, and σ(ls) is the molecular diameter that characterizes the liquid-substrate interaction, is very important in determining the friction coefficient. This parameter β, which we term the structure adhesion parameter, provides a measure of the intermolecular interaction between a liquid molecule and the substrate and also of the surface area of contact of the liquid molecule with the substrate. We find a linear dependence of μ on the structure adhesion parameter for the systems studied. We also find that increasing β leads to an increase in the vertical adhesion forces FA (the attractive force exerted by the solid surface on the liquid film). Our quantitative relationship between the nanofriction coefficient and the key parameter β which governs the vertical adhesive strength, opens up an opportunity for describing liquid flows on solid surfaces at the molecular level, with implications for the development of membrane and nanofluidic devices.

Effect of Surface Type on the Flow Characteristics in Shale Nanopores

“…Furthermore, unlike the slug-like velocity profiles in the graphene nanopore, the velocity profiles in quartz nanopore are parabolic, which are in agreement with the descriptions of the traditional Navier-Stokes equation [23,46]. Such different slip behavior of methane molecules on the quartz and graphene surface is interesting; the different liquid-solid interactions are generally regarded as the main reason, which is mainly dominated by the atom's parameters σ and ε [64,65] in Table 2 for the CH 4 molecules confined in various nanopores. In addition, the breakdown of gas molecules slippage on the quartz surface is especially owing to the inherent atomic roughness of the surface by Yu et al [43,66], especially, the potential energy roughness of the quartz surface is higher than that on graphene surface up to two magnitude of orders.…”

Friction of Ionic Liquid–Glycol Ether Mixtures at Titanium Interfaces: Negative Load Dependence

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The Influence of Lubrication and the Solid–Fluid Interaction on Thermodynamic Properties in a Nanoscopic Scratching Process

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