Temperature Dependence of Nanoscale Friction Investigated with Thermal AFM Probes

Greiner, Christian; Felts, Jonathan R.; Dai, Zhaoxin; King, William P.; Carpick, Robert W.

doi:10.1557/proc-1226-ii05-02

Cited by 4 publications

(3 citation statements)

References 32 publications

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“…By simplifying the solid interface, it is possible to decouple the effects of surface roughness from other environmental effects. In addition to fine control of force, it is possible to functionalize AFM tips to conduct current and it is relatively straightforward to modify AFM systems to control environmental conditions. − These abilities make AFM suitable to study electroadhesion between surfaces under a wide variety of conditions. Furthermore, the existence of a meniscus at the tip–sample interface has been well documented over the last few decades, even for weakly hydrophilic surfaces and low-relative humidity conditions .…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the Electrowetting Effect on the Interfacial Mechanics between Human Corneocytes and Nanoasperities

Boonpuek

Choi

et al. 2021

Langmuir

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A large subset of haptic surfaces employs electroadhesion to modulate both adhesion and friction at a sliding finger interface. The current theory of electroadhesion assumes that the applied electric field pulls the skin into stronger contact, increasing friction by increasing the real contact area, yet it is unknown what role environmental moisture plays in the effect. This paper uses atomic force microscopy (AFM)to determine the effect of humidity on the adhesion and friction between the single nanoscale asperity and individual human finger corneocytes. An analytical model of the total effective load of the AFM tip is developed to explain the humidity−voltage dependence of nanoscale adhesion and friction at contacting asperities. The results show that the electrowetting effect at the interface at high humidity accounts for 35% of the adhesive force but less than 8% of the total friction, implying that the electrowetting effect can be enhanced by optimizing surface topography to promote the formation and rupture of liquid menisci.

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Section: Introductionmentioning

confidence: 99%

Evaluation of the Electrowetting Effect on the Interfacial Mechanics between Human Corneocytes and Nanoasperities

Boonpuek

Choi

et al. 2021

Langmuir

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“…Right after the tribological tests, the copper samples were stored in a desiccator with a pressure <1 mbar, to prevent additional oxidation due to the ambient environment. [ 61–67 ]…”

Section: Methodsmentioning

confidence: 99%

Three Regimes in the Tribo‐Oxidation of High Purity Copper at Temperatures of up to 150 °C

et al. 2022

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Surface oxidation of high‐purity copper is accelerated under tribological loading. Tribo‐oxide formation at room temperature is associated with diffusion processes along defects, such as dislocations or grain boundaries. Herein, the additional influence of temperature on the tribo‐oxidation of copper is investigated. Dry, reciprocating sliding tests are performed with a variation of the sample temperature between 21 and 150 °C. Microstructural changes are monitored and analyzed with state‐of‐the‐art electron microscopy techniques. Oxide layer formation through thermal oxidation is observed for 150 °C, but not for lower temperatures. As the temperature increases from room temperature up to 100 °C, a significantly stronger tribo‐oxidation into deeper material layers and an increase in the amount of formed pores and oxides is detected. Up to 75 °C, diffusional processes of oxygen along grain boundaries and dislocation pipes are identified. Starting at 100 °C, CuO is detected. Hence, tribological loading significantly alters the CuO formation in comparison with static oxidation. Along with the CuO formation at temperatures ≥90 °C, the oxide layer thickness decreases while the friction coefficient increases. The observations broaden the understanding of the elementary mechanisms of tribo‐oxidation in copper. Eventually, this will allow to systematically customize surfaces showing tribo‐oxidation for specific tribological applications.

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“…In a liquid medium, there are several phenomena responsible for the friction behavior of the surface in the nanoscale. For instance, in humid environments, the formation of a capillary between an AFM probe and the surface resulting from Laplace pressure increases the interfacial adhesion by generating a larger contact area, consecutively increasing the friction force (Greiner et al, 2012). Further, the specific arrangement of the liquid molecules in the vicinity of layered-structure materials increases the liquid density in those regions, affecting the net interactions with the surface and, in turn, the friction force (Diao et al, 2019;Baboukani et al, 2021).…”

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confidence: 99%

Nanoscale friction characteristics of layered-structure materials in dry and wet environments

2022

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Bulk layered materials, such as graphite and molybdenum disulfide, have long been used as solid lubricants in various industrial applications. The weak interlayer van der Waals interactions in these materials generate a low shear slip-plane, which reduces the interfacial friction. The cumulative trends toward device miniaturization have increased the need for basic knowledge of the nanoscale friction of contact-mode devices containing layered materials. Further, the decomposition and degradation of bulk layered solids subjected to shear forces are detrimental to their lubricating characteristics. Layered-structure materials, such as graphene, hexagonal boron nitride, and MXenes consisting of single or few atomic layers, behave as a new class of lubricious substances when deposited at a sliding interface. The exceptional mechanical strength, thermal conductivity, electronic properties, large theoretical specific area, and chemical inertness of these materials make them ideal antifriction materials for continuous sliding interfaces, especially when operated at elevated temperatures. These properties hold great promise for widespread applications both in dry environments, such as solid film lubrication for micro/nano-electromechanical systems, nanocomposite materials, space lubrication, and optical devices, as well as in wet environments, such as desalination membranes, lubricant additives, and nanofluidic transporters. However, accurate and reliable prediction of the frictional behavior of layered-structure materials is challenging due to the complex physicochemical transformations encountered under tribostress. The presence of a liquid in the vicinity of a surface in wet-environment applications further complicates the lubrication behavior of layered-structure materials. Furthermore, insight into the origins of interfacial friction and adhesion due to localized contact interactions can be accomplished by atomic-level experimental techniques and computational methods, such as atomic force microscope (AFM) in combination with molecular dynamics (MD) and density functional theory (DFT). The AFM setup mimics asperity-asperity contact at the atomic level and can measure the friction force of layered-structure materials, whereas MD and DFT can provide insight into the chemomechanical transformations commencing at hidden interfaces, which cannot be detected by experimental methods. The objective of this review article is threefold. First, the relationship between friction and potential energy surface is examined for different layered-structure material systems, and the parameters that mainly affect the energy corrugation are interpreted in the context of reported results. Second, the atomic-scale friction mechanisms of layered-structure materials in dry or vacuum environments are discussed in light of experimental and theoretical findings, focusing on the most crucial frictional energy dissipation mechanisms. Third, the complex mechanisms affecting the nanosccale friction of layered-structure materials incorporated in liquid media are introduced for ionic, polar, and non-polar solutions.

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Temperature Dependence of Nanoscale Friction Investigated with Thermal AFM Probes

Cited by 4 publications

References 32 publications

Evaluation of the Electrowetting Effect on the Interfacial Mechanics between Human Corneocytes and Nanoasperities

Evaluation of the Electrowetting Effect on the Interfacial Mechanics between Human Corneocytes and Nanoasperities

Three Regimes in the Tribo‐Oxidation of High Purity Copper at Temperatures of up to 150 °C

Nanoscale friction characteristics of layered-structure materials in dry and wet environments

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