Friction model for the velocity dependence of nanoscale friction

Tambe, Nikhil S; Bhushan, Bharat

doi:10.1088/0957-4484/16/10/054

Cited by 151 publications

(114 citation statements)

References 50 publications

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“…Macroscale stick -slip is typically an unwanted behaviour that results in wear, chatter and unstable motion in sliding systems (Rabinowicz 1995;Bhushan 2002); however, nanoscale stick -slip dynamics are notably different (Gnecco et al 2000;Richetti et al 2001;Riedo et al 2003;Tambe & Bhushan 2005), and it has been proposed that smooth macroscopic sliding may result from uncorrelated nanoscale stick -slip (Braun et al 2005;Persson 1995 Richetti et al 2001;Tao & Bhushan 2007). We propose that wear resistance, and stable frictional adhesion forces during sliding, may emerge from the stochastic stick -slip of a population of individual fibrils with high resonant frequencies.…”

Section: Discussionmentioning

confidence: 91%

Rate-dependent frictional adhesion in natural and synthetic gecko setae

Gravish

Wilkinson

Sponberg

et al. 2009

J. R. Soc. Interface.

111

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Geckos owe their remarkable stickiness to millions of dry, hard setae on their toes. In this study, we discovered that gecko setae stick more strongly the faster they slide, and do not wear out after 30 000 cycles. This is surprising because friction between dry, hard, macroscopic materials typically decreases at the onset of sliding, and as velocity increases, friction continues to decrease because of a reduction in the number of interfacial contacts, due in part to wear. Gecko setae did not exhibit the decrease in adhesion or friction characteristic of a transition from static to kinetic contact mechanics. Instead, friction and adhesion forces increased at the onset of sliding and continued to increase with shear speed from 500 nm s 21 to 158 mm s 21. To explain how apparently fluid-like, wear-free dynamic friction and adhesion occur macroscopically in a dry, hard solid, we proposed a model based on a population of nanoscopic stick-slip events. In the model, contact elements are either in static contact or in the process of slipping to a new static contact. If stick -slip events are uncorrelated, the model further predicted that contact forces should increase to a critical velocity (V *) and then decrease at velocities greater than V*. We hypothesized that, like natural gecko setae, but unlike any conventional adhesive, gecko-like synthetic adhesives (GSAs) could adhere while sliding. To test the generality of our results and the validity of our model, we fabricated a GSA using a hard silicone polymer. While sliding, the GSA exhibited steady-state adhesion and velocity dependence similar to that of gecko setae. Observations at the interface indicated that macroscopically smooth sliding of the GSA emerged from randomly occurring stick -slip events in the population of flexible fibrils, confirming our model predictions.

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Section: Discussionmentioning

confidence: 91%

Rate-dependent frictional adhesion in natural and synthetic gecko setae

Gravish

Wilkinson

Sponberg

et al. 2009

J. R. Soc. Interface.

111

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“…The increase in friction force at high velocities is the result of asperity impacts and the corresponding high frictional energy dissipation at the sliding interface (Tambe and Bhushan 2005b). Tambe and Bhushan (2005a) have extended the ''molecular spring'' model presented by Bhushan and Liu (2001) to explain the velocity dependent increase in friction force for compliant SAM molecules. The SAM molecules reorient under the tip normal load.…”

Section: Afm Adhesion and Friction Measurements Under Ambient Conditionsmentioning

confidence: 87%

Nanotribological characterization of perfluoroalkylphosphonate self-assembled monolayers deposited on aluminum-coated silicon substrates

et al. 2006

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Aluminum-coated silicon substrates are commonly used for various micro/nanooptoelectromechanical systems (MOEMS/NOEMS) including Digital Micromirror Devices (DMD Ò ). For efficient and failure proof operation of these devices, ultra-thin lubricant films of self-assembled monolayers (SAMs) are increasingly being employed. Fluorinated molecules are known to exhibit low surface energy, adhesion, and friction, desirable for tribological applications. In this study, we investigate contact angle, surface energy, friction, adhesion, and wear properties of a perfluoroalkylphosphonate SAM and compare them with those of alkylphosphonate SAMs. The influence of relative humidity, temperature, and sliding velocity on the friction and adhesion behavior is studied. Failure mechanisms of SAMs are investigated by wear tests. These studies are expected to aid in the design and selection of proper lubricants for MOEMS/ NOEMS.

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“…At nanoscale, the traditional Amonton's law cannot be used to calculate the friction force. To analyze the running-in behavior of nanoscale friction, we adapt the model proposed by Tambe et al [20], which assumes that the nanoscale friction force between contact interfaces is a result of three components: F int due to interfacial adhesion, F def due to deformation, and F stick-slip due to stick-slip of contact interfaces.…”

Section: Sharp Drop Of Interfacial Force During a Running-in Processmentioning

confidence: 99%

Running-in process of Si-SiO x /SiO2 pair at nanoscale—Sharp drops in friction and wear rate during initial cycles

et al. 2013

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Abstract:Using an atomic force microscope, the running-in process of a single crystalline silicon wafer coated with native oxide layer (Si-SiO x ) against a SiO 2 microsphere was investigated under various normal loads and displacement amplitudes in ambient air. As the number of sliding cycles increased, both the friction force F t of the Si-SiO x /SiO 2 pair and the wear rate of the silicon surface showed sharp drops during the initial 50 cycles and then leveled off in the remaining cycles. The sharp drop in F t appeared to be induced mainly by the reduction of adhesion-related interfacial force between the Si-SiO x /SiO 2 pair. During the running-in process, the contact area of the Si-SiO x /SiO 2 pair might become hydrophobic due to removal of the hydrophilic oxide layer on the silicon surface and the surface change of the SiO 2 tip, which caused the reduction of friction force and the wear rate of the Si-SiO x /SiO 2 pair. A phenomenological model is proposed to explain the running-in process of the Si-SiO x /SiO 2 pair in ambient air. The results may help us understand the mechanism of the running-in process of the Si-SiO x /SiO 2 pair at nanoscale and reduce wear failure in dynamic microelectromechanical systems (MEMS).

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Friction model for the velocity dependence of nanoscale friction

Cited by 151 publications

References 50 publications

Rate-dependent frictional adhesion in natural and synthetic gecko setae

Rate-dependent frictional adhesion in natural and synthetic gecko setae

Nanotribological characterization of perfluoroalkylphosphonate self-assembled monolayers deposited on aluminum-coated silicon substrates

Running-in process of Si-SiO x /SiO2 pair at nanoscale—Sharp drops in friction and wear rate during initial cycles

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