Measurements of Anisotropic (Off‐Axis) Friction‐Induced Motion

Kristiansen, Kai; Banquy, Xavier; Zeng, Hongbo; Charrault, Eric; Giasson, Suzanne; Israelachvili, Jacob N.

doi:10.1002/adma.201201566

Cited by 21 publications

(16 citation statements)

References 33 publications

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“…Friction anisotropy, whereby a friction force is detected perpendicular as well as parallel to the sliding direction, has been observed in previous experiments [69] and NEMD simulations [70] of strongly-confined (< 3 layers) n-alkane films. However, friction anisotropy was not observed for the relatively thicker n-alkane films studied here at high pressure.…”

Section: Frictionsupporting

confidence: 57%

Behaviour of n-alkanes confined between iron oxide surfaces at high pressure and shear rate: A nonequilibrium molecular dynamics study

Restrepo

Eijk

Ewen

2019

Tribology International

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The behaviour of n-alkanes confined and sheared between iron oxide surfaces has been studied using nonequilibrium molecular dynamics simulations. The molecular extension, orientation, film structure, flow, and friction have been investigated for a range of n-alkanes chain lengths under conditions representative of the elastohydrodynamic lubrication regime. At high pressure, the molecules show strong layering and long-range order, suggesting solid-like films. Conversely, high shear rates result in less elongated, layered, and ordered molecules; indicating more liquid-like films. Although Couette flow is usually observed for short n-alkanes, the flow is often non-linear for long n-alkanes. The friction coefficient increases logarithmically with shear rate, but the slope decreases with increasing pressure such that it becomes insensitive to shear rate for long n-alkanes.

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Section: Frictionsupporting

confidence: 57%

Behaviour of n-alkanes confined between iron oxide surfaces at high pressure and shear rate: A nonequilibrium molecular dynamics study

Restrepo

Eijk

Ewen

2019

Tribology International

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“…2 C and D or PBS (Sigma) for all other experiments were injected as a reservoir. Loading and shearing were conducted with course-control micrometer and bimorph slider, respectively, whereas the friction forces and loads were measured using a recently developed 3D sensor/actuator (48,50). Because of the opacity of the samples, optical interferometry could not be used as in standard SFAFringes of Equal Chromatic Order (FECO) experiments.…”

Section: Methodsmentioning

confidence: 99%

Stick-slip friction and wear of articular joints

Lee¹,

Banquy²,

Israelachvili

2013

Proc. Natl. Acad. Sci. U.S.A.

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Stick-slip friction was observed in articular cartilage under certain loading and sliding conditions and systematically studied. Using the Surface Forces Apparatus, we show that stick-slip friction can induce permanent morphological changes (a change in the roughness indicative of wear/damage) in cartilage surfaces, even under mild loading and sliding conditions. The different load and speed regimes can be represented by friction maps-separating regimes of smooth and stick-slip sliding; damage generally occurs within the stick-slip regimes. Prolonged exposure of cartilage surfaces to stick-slip sliding resulted in a significant increase of surface roughness, indicative of severe morphological changes of the cartilage superficial zone. To further investigate the factors that are conducive to stick-slip and wear, we selectively digested essential components of cartilage: type II collagen, hyaluronic acid (HA), and glycosaminoglycans (GAGs). Compared with the normal cartilage, HA and GAG digestions modified the stick-slip behavior and increased surface roughness (wear) during sliding, whereas collagen digestion decreased the surface roughness. Importantly, friction forces increased up to 2, 10, and 5 times after HA, GAGs, and collagen digestion, respectively. Also, each digestion altered the friction map in different ways. Our results show that (i) wear is not directly related to the friction coefficient but (ii) more directly related to stick-slip sliding, even when present at small amplitudes, and that (iii) the different molecular components of joints work synergistically to prevent wear. Our results also suggest potential noninvasive diagnostic tools for sensing stick-slip in joints.arthritis | biolubrication | biointerface | boundary lubrication O steoarthritis (OA) is widely present in the elderly (1, 2) as well as people with obesity (3). Despite the prevalence of OA, the physical and biological events that trigger articular cartilage damage are still poorly understood, especially at the molecular and submicron levels; so far, no model has been successful in describing the mechanistic cascade that leads to cartilage wear and irreversible loss (4). There are no available techniques to detect the onset of joint diseases, and tracking the progression of these diseases remains a major challenge (5).One of the key challenges for establishing a model that can successfully track the cause and progression of joint diseases is in the fact that articular joints are designed to function under an extremely large range of mechanical, dynamic, and environmental conditions, under any of which a priori damage can occur. Many scientists have, therefore, focused their efforts on specific physiological regimes under which joints would be severely subjected to mechanical damage caused by a failure of the lubrication mechanism at the submicron level.The most important and also least understood physiological regime associated with damage is referred to as the boundary lubrication (BL) regime, where two sliding surfaces and the mo...

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“…1,2 It has been investigated profoundly at both macroscopic and atomic length scales. [3][4][5][6][7][8][9][10] For instance the shape and frequency of well-controlled corrugations were studied at surfaces made from silicone rubber 11 or epoxides. 12 However, modern and advanced technologies are not satised in maintaining the friction at a constant value; they require modulation between different levels activated by external triggers.…”

Section: Introductionmentioning

confidence: 99%

Light controlled friction at a liquid crystal polymer coating with switchable patterning

Liu

Broer

2014

Soft Matter

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We describe a new methodology that enables dynamical control of motion through modulating the friction at coating surfaces by exposing to UV light. The principle is based on reversible switching of the surface topographies of the coating by light. The coating surface transfers from flat in the dark to corrugated in the presence of UV by forming regular ridge-like line gratings. Both the static and the kinetic friction coefficient are investigated in a dynamic manner by switching between the off (flat surface) and the activated (with ridges) state. By dynamically changing the friction, we are able to bring the sample from a static state into motion via UV exposure. When in motion, the friction coefficient can be altered further by modulating the light conditions. For example, a smooth sliding can transfer into an interlocking state, or vice versa. Moreover, we can dynamically reduce the contact area in the interface and thus lowering friction forces.

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Measurements of Anisotropic (Off‐Axis) Friction‐Induced Motion

Cited by 21 publications

References 33 publications

Behaviour of n-alkanes confined between iron oxide surfaces at high pressure and shear rate: A nonequilibrium molecular dynamics study

Behaviour of n-alkanes confined between iron oxide surfaces at high pressure and shear rate: A nonequilibrium molecular dynamics study

Stick-slip friction and wear of articular joints

Light controlled friction at a liquid crystal polymer coating with switchable patterning

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