Impact of water on the lubricating properties of hexadecane at the nanoscale

Cafolla, Clodomiro; Voïtchovsky, Kislon

doi:10.1039/d0nr03642k

Cited by 18 publications

(19 citation statements)

References 68 publications

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“…The probes were found to have a flexural spring constant in the range 1.0–4.0 N/m and a resonance frequency of ~ 400 kHz in water. The values are in agreement with the literature 20 , 77 . The cantilever oscillation was photo-thermally driven so as to ensure greater stability.…”

Section: Methodssupporting

confidence: 93%

“…The AFM probes were Arrow UHF silicon nitride cantilevers (Nanoworld, Switzerland). The thermal spectrum of the cantilever was used to perform the flexural calibration of the cantilevers 76 values are in agreement with the literature 20,77 . The cantilever oscillation was photo-thermally driven so as to ensure greater stability.…”

Section: Methodssupporting

confidence: 72%

“…Examples span from biological enzymes 13 to sliding surfaces 7 , nanotubes 8 and graphene oxide membranes 14 .The behaviour of ions at solid-liquid interfaces is often described using continuum models such as the Gouy-Chapman-Stern 15 or the Dynamic Stern Layer 16 models. While highly successful for describing macroscopic systems at equilibrium, these models can fall short at the nanoscale when atomistic details such as specific solvation effects and local defects or singularities become important 7,15,[17][18][19][20][21][22] . For example, the specific organisation of ions into domains is common in biomedical and technological processes such as the effects of lithium on mitochondrial membranes 23,24 and ion transport through nanofluidic channels 8,25 .…”

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confidence: 99%

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Real-time tracking of ionic nano-domains under shear flow

Cafolla

Voïtchovsky

2021

Sci Rep

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The behaviour of ions at solid–liquid interfaces underpins countless phenomena, from the conduction of nervous impulses to charge transfer in solar cells. In most cases, ions do not operate as isolated entities, but in conjunction with neighbouring ions and the surrounding solution. In aqueous solutions, recent studies suggest the existence of group dynamics through water-mediated clusters but results allowing direct tracking of ionic domains with atomic precision are scarce. Here, we use high-speed atomic force microscopy to track the evolution of Rb+, K+, Na+ and Ca2+ nano-domains containing 20 to 120 ions adsorbed at the surface of mica in aqueous solution. The interface is exposed to a shear flow able to influence the lateral motion of single ions and clusters. The results show that, when in groups, metal ions tend to move with a relatively slow dynamics, as can be expected from a correlated group motion, with an average residence timescale of ~ 1–2 s for individual ions at a given atomic site. The average group velocity of the clusters depends on the ions’ charge density and can be explained by the ion’s hydration state. The lateral shear flow of the fluid is insufficient to desorb ions, but indirectly influences the diffusion dynamics by acting on ions in close vicinity to the surface. The results provide insights into the dynamics of ion clusters when adsorbed onto an immersed solid under shear flow.

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Section: Methodssupporting

confidence: 93%

Section: Methodssupporting

confidence: 72%

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confidence: 99%

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Real-time tracking of ionic nano-domains under shear flow

Cafolla

Voïtchovsky

2021

Sci Rep

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“…Indeed, previous AFM experiments have shown that water nanodroplets in n-hexadecane increase friction. 116 Snapshots of these water structures in the fully-functionalised contacts are shown at different sliding velocities in the Supplementary Material (Fig. S7).…”

Section: Resultsmentioning

confidence: 99%

Nanoscale Friction of Biomimetic Hair Surfaces

Weiand

Ewen

Roiter

et al. 2022

Preprint

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We investigate the nanoscale friction between biomimetic hair surfaces using chemical colloidal probe atomic force microscopy experiments and nonequilibrium molecular dynamics simulations. In the experiments, friction is measured between water-lubricated silica surfaces functionalised with monolayers of either octadecyl or sulfonate groups, which are representative of the surfaces of virgin and ultimately bleached hair, respectively. In the simulations, friction is monitored between coarse-grained model hair surfaces with different levels of chemical damage, where different fractions of grafted lipid molecules are randomly replaced with sulfonate groups. The sliding velocity dependence of friction can be described using an extended stress-augmented thermally activation model. As the damage level increases, the friction generally increases, but its sliding velocity-dependence decreases. At low sliding speeds, which are closer to those encountered physiologically and experimentally, we observe a monotonic increase of friction with the damage ratio, which is consistent with our new experiments using biomimetic surfaces and previous ones using real hair. This observation demonstrates that modified surface chemistry, rather than roughness changes or subsurface damage, control the increase in nanoscale friction of damaged hair. We expect the experimental and computational model surfaces proposed here to be useful to screen the tribological performance of hair care formulations.

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“…Pure water and lubricating oil with trace quantities of water are also potential candidates for future lubricants due to their eco-friendly nature. 14,19,20 A recent experiment 20 conducted on hexadecane with trace quantities of water confined between mica walls demonstrated that the nucleation of water nanodroplets at the surface is induced by an increase in the temperature of the system, and the addition of amphiphilic molecules such as oleic acids to the lubricant suppresses this nucleation. Additionally, research conducted on the viscosity behavior of four different phenyl ether lubricants under nanoslit confinement using RSM indicated a significant increase in the viscosity with the decrease in the surface separation ( 2 nm), and the magnitude of the viscosity correlation between the bulk and the confined systems was reversed.…”

Section: Introductionmentioning

confidence: 99%

Correlation between ordering and shear thinning in confined liquids

Kobayashi¹,

Arai²,

Yasuoka³

2022

Preprint

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Despite the extensive research that has been conducted for decades on the behavior of confined liquids, detailed knowledge of this phenomenon, particularly in the mixed/boundary lubrication regime, remains limited. This can be attributed to several factors including the difficulty of direct experimental observations of the behavior of lubricant molecules under non-equilibrium conditions, the high computational cost of molecular simulations to reach steady state, and the low signal-to-noise ratio at extremely low shear rates corresponding to actual operating conditions. To this end, we studied the correlation between the structure formation and shear viscosity of octamethylcyclotetrasiloxane confined between two mica surfaces in a mixed/boundary lubrication regime. Three different surface separations corresponding to two-, three-, and five-layered structures were considered to analyze the effect of confinement. The orientational distributions with one specific peak for n = 2 and two distributions, including a parallel orientation with the surface normal for n > 2, were observed at rest. The confined liquids exhibited a distinct shear-thinning behavior independent of surface separations for a relatively low sliding velocity, V x 10 −1 m/s. However, the shear viscosities at V x 10 −1 m/s depended on the number of layered structures. Newtonian behavior was observed with a further increase in the sliding velocity. Furthermore, we found a strong correlation between the degree of molecular orientation and the shear viscosity of the confined liquids. The magnitude of the shear viscosity of the confined liquids can primarily be determined by the degree of molecular orientation, and shear-thinning originates from the vanishing of specific orientational distributions with increasing sliding velocity.

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Impact of water on the lubricating properties of hexadecane at the nanoscale

Abstract:
Nano-rheological measurements quantify the effect of ambient humidity on the local lubricating properties of hexadecane on hydrophilic mica as a function of temperature.

Cited by 18 publications

References 68 publications

Real-time tracking of ionic nano-domains under shear flow

Real-time tracking of ionic nano-domains under shear flow

Nanoscale Friction of Biomimetic Hair Surfaces

Correlation between ordering and shear thinning in confined liquids

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Impact of water on the lubricating properties of hexadecane at the nanoscale

Abstract: Nano-rheological measurements quantify the effect of ambient humidity on the local lubricating properties of hexadecane on hydrophilic mica as a function of temperature.

Cited by 18 publications

References 68 publications

Real-time tracking of ionic nano-domains under shear flow

Real-time tracking of ionic nano-domains under shear flow

Nanoscale Friction of Biomimetic Hair Surfaces

Correlation between ordering and shear thinning in confined liquids

Contact Info

Product

Resources

About

Abstract:
Nano-rheological measurements quantify the effect of ambient humidity on the local lubricating properties of hexadecane on hydrophilic mica as a function of temperature.