Driven dynamics of simplified tribological models

Vanossi, Andrea; Braun, O. M.

doi:10.1088/0953-8984/19/30/305017

Cited by 58 publications

(51 citation statements)

References 87 publications

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“…3a} shows that, during passage of the compression zone, each colloid is displaced by one substrate lattice constant with a small time delay along the particle chain. Such a correlated particle motion is characteristic for a running kink 29 .JO, which is illustrated for a one-dimensional system in Fig. 3c.…”

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confidence: 88%

Observation of kinks and antikinks in colloidal monolayers driven across ordered surfaces

2011

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Friction between solids is responsible for many phenomena such as earthquakes, wear or crack propagation 1-4 . Unlike macroscopic objects, which only touch locally owing to their surface roughness, spatially extended contacts form between atomically flat surfaces. They are described by the FrenkelKontorova model, which considers a monolayer of interacting particles on a periodic substrate potential 5-8 . In addition to the well-known stick-slip motion, such models also predict the formation of kinks and antikinks 9-12 , which greatly reduce the friction between the monolayer and the substrate. Here, we report the direct observation of kinks and antikinks in a two-dimensional colloidal crystal that is driven across different types of ordered substrate. We show that the frictional properties only depend on the number and density of such excitations, which propagate through the monolayer along the direction of the applied force. In addition, we also observe kinks on quasicrystalline surfaces, which demonstrates that they are not limited to periodic substrates but occur under more general conditions.Friction is important in our daily life and it is not surprising that systematic investigations date back more than 300 years. According to Amontons and Coulomb, friction between solids is proportional to the normal force but independent of the contact area. This intriguing result was explained by realizing that macroscopic objects touch at asperities that are deformed by the normal force 13 . A different situation occurs when atomically flat surfaces slide against each other, as for example encountered in micro-or nanoelectromechanical systems. Then, extended contacts arise and the degree of commensurability between the surfaces determines the friction. For commensurate conditions, a dissipative stick-slip motion is typically observed 14 . In contrast, at incommensurate interfaces, atomic friction studies revealed a superlubrication regime, where the friction coefficient vanishes 15,16 . This behaviour can be explained by simple mechanical models such as the FrenkelKontorova model, a generalized Prandtl-Tomlinson scheme or the double-chain model [17][18][19][20] . In the Frenkel-Kontorova approach the interface between two solids is described by a monolayer of elastically interacting beads on a periodic substrate potential [5][6][7][8] . In addition to stick-slip motion, the Frenkel-Kontorova model also predicts the formation of topological solitons, so-called kinks and antikinks [9][10][11][12] . These excitations are believed to dominate the frictional properties at atomic length scales because they provide an efficient mechanism for mass transport; so far, such excitations have never been observed in sliding friction experiments 21 .Here, we report the observation of kinks and antikinks in a colloidal system that is driven across commensurate and incommensurate substrate potentials. We use highly charged polystyrene spheres with radius R = 1.95 μm, which are suspended in water. In the presence of gravitational and op...

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confidence: 88%

Observation of kinks and antikinks in colloidal monolayers driven across ordered surfaces

2011

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“…This defines, in the thermodynamic limit (N → ∞), a continuum set of ground states that can be reached adiabatically through nonrigid displacement of chain atoms at no energy cost with a consequent vanishing static friction [2,3]. [20]. The equations of motion have been integrated numerically using a Velocity-Verlet algorithm, focusing on the case at T=0.…”

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confidence: 99%

Critical Length Limiting Superlow Friction

Benassi

Vanossi

et al. 2015

Phys. Rev. Lett.

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Since the demonstration of super-low friction (superlubricity) in graphite at nanoscale, one of the main challenges in the field of nano-and micro-mechanics was to scale this phenomenon up. A key question to be addressed is to what extent superlubricity could persist, and what mechanisms could lead to its failure. Here, using an edge-driven Frenkel-Kontorova model, we establish a connection between the critical length above which superlubricity disappears and both intrinsic material properties and experimental parameters. A striking boost in dissipated energy with chain length emerges abruptly due to a high-friction stick-slip mechanism caused by deformation of the slider leading to a local commensuration with the substrate lattice. We derived a parameter-free analytical model for the critical length that is in excellent agreement with our numerical simulations.Our results provide a new perspective on friction and nano-manipulation and can serve as a theoretical basis for designing nano-devices with super-low friction, such as carbon nanotubes.

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“…19,20 The two periodicities a 0 and a sub define the coverage = a sub / a 0 . For convenience we take a sub as the unit length, F sub as the force unit, and the mass m of the particles as the mass unit.…”

Section: Modelmentioning

confidence: 99%

AFM dissipation topography of soliton superstructures in adsorbed overlayers

et al. 2010

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In the atomic force microscope, the nanoscale force topography of even complex surface superstructures is extracted by the changing vibration frequency of a scanning tip. An alternative dissipation topography with similar or even better contrast has been demonstrated recently by mapping the ͑x , y͒-dependent tip damping but the detailed damping mechanism is still unknown. Here we identify two different tip dissipation mechanisms: local mechanical softness and hysteresis. Motivated by recent data, we describe both of them in a onedimensional model of Moiré superstructures of incommensurate overlayers. Local softness at "soliton" defects yields a dissipation contrast that can be much larger than the corresponding density or corrugation contrast. At realistically low vibration frequencies, however, a much stronger and more effective dissipation is caused by the tip-induced nonlinear jumping of the soliton, naturally developing bistability and hysteresis. Signatures of this mechanism are proposed for experimental identification.

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Driven dynamics of simplified tribological models

Cited by 58 publications

References 87 publications

Observation of kinks and antikinks in colloidal monolayers driven across ordered surfaces

Observation of kinks and antikinks in colloidal monolayers driven across ordered surfaces

Critical Length Limiting Superlow Friction

AFM dissipation topography of soliton superstructures in adsorbed overlayers

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