Experimental Study and Modeling of Boundary Lubricant Polyelectrolyte Films

Bouchet, André du; Cazeneuve, Colette; Baghdadli, Nawel; Luengo, Gustavo S.; Drummond, Carlos

doi:10.1021/acs.macromol.5b00151

Cited by 15 publications

(20 citation statements)

References 43 publications

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“…In the first regime of hydrodynamic lubrication (blue zone, (i)), tangential frictional forces are small and arise purely from hydrodynamic interactions, whereas a normal load F N can be sustained due to entropic repulsion of the brushes. This situation results in a friction coefficient as low as μ ≈0.02, as observed in previous friction studies on polymer brushes in SFA2931323334.…”

Section: Resultssupporting

confidence: 72%

Pairwise frictional profile between particles determines discontinuous shear thickening transition in non-colloidal suspensions

et al. 2017

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The process by which sheared suspensions go through a dramatic change in viscosity is known as discontinuous shear thickening. Although well-characterized on the macroscale, the microscopic mechanisms at play in this transition are still poorly understood. Here, by developing new experimental procedures based on quartz-tuning fork atomic force microscopy, we measure the pairwise frictional profile between approaching pairs of polyvinyl chloride and cornstarch particles in solvent. We report a clear transition from a low-friction regime, where pairs of particles support a finite normal load, while interacting purely hydrodynamically, to a high-friction regime characterized by hard repulsive contact between the particles and sliding friction. Critically, we show that the normal stress needed to enter the frictional regime at nanoscale matches the critical stress at which shear thickening occurs for macroscopic suspensions. Our experiments bridge nano and macroscales and provide long needed demonstration of the role of frictional forces in discontinuous shear thickening.

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Section: Resultssupporting

confidence: 72%

Pairwise frictional profile between particles determines discontinuous shear thickening transition in non-colloidal suspensions

et al. 2017

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“…We have also plotted separately the contributions of both terms in (9), namely the contribution of end effects for a finite-length cylinder, and the elastohydrodynamic contribution for an infinite cylinder, as shown in Fig. 4(a).…”

Section: Discussionmentioning

confidence: 99%

“…The interplay between lubricated flow and deformable surfaces is ubiquitous in nature and engineering in settings spanning a broad range of length scales, e.g. earthquakes [1], avalanches [2], landslides [3], lubrication of cartilaginous and artificial joints [4][5][6][7][8][9] or industrial bearings [10]. Often, this elastohydrodynamic coupling is seen in the presence of confined flow where pressure gradients are likely to be large.…”

Section: Introductionmentioning

confidence: 99%

Rotation of a submerged finite cylinder moving down a soft incline

et al. 2020

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A submerged finite cylinder moving under its own weight along a soft incline lifts off and slides at a steady velocity while also spinning. Here, we experimentally quantify the steady spinning of the cylinder and show theoretically that it is due to a combination of an elastohydrodynamic torque generated by flow in the variable gap, and the viscous friction on the edges of the finitelength cylinder. The relative influence of the latter depends on the aspect ratio of the cylinder as well as the deformability of the substrate, which we express in term of a single scaled compliance parameter. By varying this compliance parameter, we show that our experimental results are consistent with a transition from an edge-effect dominated regime for short cylinders to a gapdominated elastohydrodynamic regime when the cylinder is very long.

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“…Despite the above theoretical literature, experimental evidence for such an elastohydrodynamic lift force remains recent and scarce 28,29 . A preliminary qualitative observation was reported in the context of smart lubricant and polyelectrolytes 30 . A first quantitative study, involving the sliding of an immersed macroscopic cylinder along an inclined plane, precoated with a thin layer of gel, showed an effective reduction of friction induced by the lift force 31 .…”

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confidence: 96%

Direct Measurement of the Elastohydrodynamic Lift Force at the Nanoscale

et al. 2020

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Friction in soft and wet contacts is crucial for industry and engineering, but it might also play a central role for the motion of various physiological and biological entities, as well as for the nanorheology of very soft materials. Here, we report on the first direct measurement of the elastohydrodynamic lift force acting on a sphere moving within a viscous liquid, near and along a soft substrate under nanometric confinement. Using atomic force microscopy, the lift force is probed as a function of the gap size, for various driving velocities, viscosities, and stiffnesses. The results are in excellent agreement with scaling arguments and a novel quantitative model developed from the soft lubrication theory, in linear elasticity, and for small compliances. For larger compliances, or equivalently for smaller confinement length scales, a saturation of the lift force is observed and its empirical scaling law is discussed.

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Experimental Study and Modeling of Boundary Lubricant Polyelectrolyte Films

Cited by 15 publications

References 43 publications

Pairwise frictional profile between particles determines discontinuous shear thickening transition in non-colloidal suspensions

Pairwise frictional profile between particles determines discontinuous shear thickening transition in non-colloidal suspensions

Rotation of a submerged finite cylinder moving down a soft incline

Direct Measurement of the Elastohydrodynamic Lift Force at the Nanoscale

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