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The lubrication properties of nanoconfined liquids underpin countless natural and industrial processes. However, our current understanding of lubricated friction is still limited, especially for nonideal interfaces exhibiting nanoscale chemical and topographical defects. Here, we use atomic force microscopy to explore the equilibrium and dynamical behavior of a model lubricant, squalane, confined between a diamond tip and graphite in the vicinity of an atomic step. We combine high-resolution imaging of the interface with highly localized shear measurements at different velocities and temperatures to derive a quantitative picture of the lubricated friction around surface defects. We show that defects tend to promote local molecular order and increase friction forces by reducing the number of stable molecular configurations in their immediate vicinity. The effect is general, can propagate over hundreds of nanometers, and can be quantitatively described by a semiempirical model that bridges the molecular details and mesoscale observations.
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http://dx.doi.org/10.1126/sciadv.aaz3673 | DOI Listing |
J Texture Stud
October 2025
College of Automation Engineering, Northeast Electric Power University, Jilin, China.
Astringency is a complex oral sensation characterized by dryness and constriction in the mouth. It is typically induced by polyphenol-rich foods and beverages such as wine and tea. The quantitative assessment of astringency intensity has become a prominent research focus in the food science field.
View Article and Find Full Text PDFSmall
September 2025
Department of Materials Science, Key Laboratory of Automobile Materials, MOE and State Key Laboratory of High Pressure and Superhard Materials, International Center of Future Science, Jilin University, Changchun, 130012, China.
Molybdenum disulfide (MoS) exhibits excellent lubrication capacity rooted in its layered structure, but it suffers significant structural and functional deterioration due to oxidation in ambient environments, limiting its applications. Concerted efforts are focused on enhancing the antioxidation ability of MoS, but challenges remain. This work conceptualizes and demonstrates a contrarian design of MoS-based film via metal incorporation and oxidation based on consideration of key fundamental principles of thermodynamics, chemistry, and physical mechanics.
View Article and Find Full Text PDFACS Appl Mater Interfaces
September 2025
State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China.
Near-zero wear on engineering steel surfaces is a promising solution to extend the service life of mechanical equipment. However, most existing strategies offer only limited low wear under particular conditions and friction pairs. To address this, we design a polymer-based proton ionic liquid (PPILs) lubricant, leveraging the proton exchange between polyethylenimine, which is rich in active nitrogen groups, and bis(2-ethylhexyl) phosphate.
View Article and Find Full Text PDFLangmuir
September 2025
School of Materials Science and Engineering, North Minzu University, Yinchuan 750021, P. R. China.
Understanding the mechanism of action of graphene oxide (GO)-based lubrication materials is of great significance to effectively suppress the surface damage accumulation of bearing steel during service. However, GO typically exhibits weak interfacial adsorption and poor dispersion stability, severely limiting its ability to form a dynamic tribofilm during friction. In this study, we synthesized an efficient lubricant, oleylamine-grafted chlorinated graphene (OA/Cl-GO), using GO as the carrier and introducing lipophilic terminal groups through chlorination and interfacial covalent modification.
View Article and Find Full Text PDFPLoS One
September 2025
School of Dental, Health and Care Professions, University of Portsmouth, Portsmouth, United Kingdom.
This study investigates the impact of a sweetened acidic beverage, an apple juice (J) consumption on the tribological properties, viscoelasticity, and protein concentration/ composition of human saliva. Using a combination of tribological measurements, quartz crystal microbalance with dissipation monitoring (QCM-D), and protein analysis, we assessed how J may affect saliva's lubricating behaviour and adsorbed salivary film characteristics compared to water (control). Tribological results revealed that saliva (collected from 32 healthy adults) exposed to water or J exhibited increased friction when compared to unstimulated whole mouth saliva (uWMS), particularly within the boundary lubrication regime.
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