Dynamic shear force microscopy of viscosity in nanometer-confined hexadecane layers

Krass, Marc-Dominik; Gosvami, Nitya Nand; Carpick, Robert W.; Müser, Martin H.; Bennewitz, Roland

doi:10.1088/0953-8984/28/13/134004

Cited by 17 publications

(18 citation statements)

References 31 publications

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“…In the framework of a densityfunctional theory-based description [12][13][14][15], one may discern that the one-particle density of a confined liquid holds a similar functional form as that of the two-particle density of a bulk liquid. Such a similarity has been confirmed by recent simulation works [16,17].…”

Section: Introductionsupporting

confidence: 78%

History-Dependent Stress Relaxation of Liquids under High-Confinement: A Molecular Dynamics Study

Gao

2022

Lubricants

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When liquids are confined into a nanometer-scale slit, the induced layering-like film structure allows the liquid to sustain non-isotropic stresses and thus be load-bearing. Such anisotropic characteristics of liquid under confinement arise naturally from the liquids’ wavenumber dependent compressibility, which does not need solidification to take place as a prerequisite. In other words, liquids under confinement can still retain fluidity with molecules being (sub-)diffusive. However, the extensively prolonged structural relaxation times can cause hysteresis of stress relaxation of confined molecules in response to the motions of confining walls and thereby rendering the quasi-static stress tensors history-dependent. In this work, by means of molecular dynamics, stress tensors of a highly confined key base-oil component, i.e., 1-decene trimer, are calculated after its relaxation from being compressed and decompressed. A maximum of 77.1 MPa normal stress discrepancy has been detected within a triple-layer boundary film. Analyses with respect to molecular morphology indicate that among the effects (e.g., confinement, molecular structure, and film density) that can potentially affect confined stresses, the ordering status of the confined molecules plays a predominant role.

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Section: Introductionsupporting

confidence: 78%

History-Dependent Stress Relaxation of Liquids under High-Confinement: A Molecular Dynamics Study

Gao

2022

Lubricants

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show abstract

“…In the framework of a density-functional theory based description [12][13][14][15], one may discern that one-particle density of a confined liquid holds a similar functional form as that of the two-particle density of a bulk liquid. Such a similarity has been confirmed by recent simulation works [16,17].…”

Section: Introductionsupporting

confidence: 78%

“…Second, undulation, as an indicative of transition of monolayers from (n±1) to n, appears only when the molecules are expelled (during compression). Such collective behavior of molecules in response to the external forces, often being described as layer-by-layer transition [16,48], is, however, not detected in the case of decompression even after the system pre-equilibrated for 100 ns before unloading (blue dashed curve). This simply suggests that the current displacing rate (0.2 m/s) is much too fast for molecules to flow and then to restructure into analogous arrangements within the confining geometry.…”

Section: Solvation Forcementioning

confidence: 99%

History-dependent Stress Relaxation of Liquids Under High-confinement: A Molecular Dynamics Study

Gao¹

2021

Preprint

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When liquids are confined into nanometer-scale slit, the induced layering-like film structure allows the liquid to sustain non-isotropic stresses and thus being load-bearing. Such anisotropic characteristics of liquid under confinement arise naturally from the liquids’ wave number dependent compressibility that does not need solidification to take place as a prerequisite. In other words, liquids under confinement can still remain fluidity with molecules being (sub-)diffusive. However, the extensively prolonged structural relaxation time can cause hysteresis of stress relaxation of confined molecules in response to the motions of confining walls and thereby yield the quasi-static stress tensor history-dependent. In this work, by means of molecule dynamics, the discrepancy of stress tensor of a highly confined key base-oil component, i.e. 1-decene trimer, is captured after its relaxation from being compressed and decompressed. The results indicate that among the effects (e.g. confinement, molecular structure, and film density) that can potentially affect confined stress tensor, the ordering status of the confined molecules plays a predominant role.

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“…Using ρ y N (y) = ρ 0 cos ( This length is remarkable since the solvation forces show similar penetration depths in atomic force microscopy (AFM) and SFA experiments for a number of different liquids. 67,[76][77][78][79] It should be noted that the effective range of solvation forces is strongly influenced by chain entanglements in polymers. For adsorbed polymers on surfaces, the characteristic length of their repulsive forces is scaled by the molecular weight M 0.6 and, thus, can influence much larger distances of ~ 200 nm.…”

Section: Nanotube At the Interfacementioning

confidence: 99%

Polymeric Solvation Shells around Nanotubes: Mesoscopic Simulation of Interfaces in Nanochannels

Gooneie

Hufenus

2019

Macromolecules

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Interfacial interactions in biphasic polymeric fluids confined in a nano-channel are studied using dissipative particle dynamics. The effects of an arrested nanotube at the interfaces of short-chain polymer models are elucidated and its interactions with the polymers are varied systematically. The results confirm the experimental notion that a particle can bear an excess of anisotropic interfacial stresses and consequently stabilize interface curvatures. In the presence of limited capillary effects in nanofluidic channels, the solvation shells in the vicinity of the nanotube and their related interactions become more dominant. The solvation shells are characterized by the density oscillations around the nanotube. While the oscillation intensity depends on the polymer-nanotube interactions, its characteristic length is only a function of the molecular structure of the polymer. The oscillations disappear within a certain number of shells away from the nanotube that is comparable to experimental values for low molecular weight liquids. Detailed analyses of the interface shape based on capillary wave theory reveal the impacts of such solvation forces. This study offers insights into how the polymeric solvation shells around nanoparticles can influence the interface shape, the nanoparticle-nanoparticle interactions, as well as the nanoparticle-wall interactions. Our findings can lead to promising applications in nanofluidics and in drug delivery using nanoparticles.

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Dynamic shear force microscopy of viscosity in nanometer-confined hexadecane layers

Cited by 17 publications

References 31 publications

History-Dependent Stress Relaxation of Liquids under High-Confinement: A Molecular Dynamics Study

History-Dependent Stress Relaxation of Liquids under High-Confinement: A Molecular Dynamics Study

History-dependent Stress Relaxation of Liquids Under High-confinement: A Molecular Dynamics Study

Polymeric Solvation Shells around Nanotubes: Mesoscopic Simulation of Interfaces in Nanochannels

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