Abstract:In order to test recently predicted ballistic nanofriction (ultra-low drag and enhanced lubricity) of gold nanocrystals on graphite at high surface speeds, we use the quartz microbalance technique to measure the impact of deposition of gold nanocrystals on graphene. We analyze our measurements of changes in frequency and dissipation induced by nanocrystals using a framework developed for friction of adatoms on various surfaces. We find the lubricity of gold nanocrystals on graphene to be even higher than that … Show more
“…Therefore, this clearly explains the significant anisotropic effect of friction during the sliding process [ 45 – 47 ]. The finding that the friction force decreases with the decrease of graphene-substrate interaction strength (energy corrugation) is consistent with the MD simulations [ 16 ] and QCM experiment [ 17 ]. Fig.…”
Section: Resultssupporting
confidence: 87%
“…At the same time, some scholars have also been devoted to studying the friction of graphene and/or gold using other techniques. Quartz crystal microbalance (QCM) technique was employed to study the lubricity of gold on graphene [ 16 ] and the sliding friction of solid xenon film on graphene/Ni(111) substrate [ 17 ]. Both QCM experiments and molecular dynamics (MD) simulations show that the friction of an incommensurate Kr monolayer on Au follows a viscous friction law [ 18 , 19 ].…”
In this paper, we investigate the friction behaviors of graphene flakes sliding on a gold substrate using molecular dynamics simulations. The effects of flake size, flake shape, relative rotation angle between flake and substrate, and crystal orientation of substrate on the friction process are thoroughly studied. It is found that under the same load, the average friction forces per atom are smaller for a bigger graphene flake, which exhibits an obvious size effect. It is also shown that flake shape is critical in determining the friction in the sliding process. The average friction forces per atom for the square flake are much bigger than those for the triangular and round flakes. Moreover, the average friction forces per atom for the triangular flake are the smallest. We also find that the orientation of graphene flake relative to gold substrate plays a vital role in the friction process. The friction forces for the graphene flake sliding along the armchair direction are much bigger than those for the flakes with rotation. In addition, it is also found that single crystalline gold substrate exhibits a significant anisotropic effect of friction, which is attributed to the anisotropic effect of potential energy corrugation. These understandings not only shed light on the underlying mechanisms of graphene flake sliding on the gold substrates but also may guide the design and fabrication of nanoscale graphene-based devices.
“…Therefore, this clearly explains the significant anisotropic effect of friction during the sliding process [ 45 – 47 ]. The finding that the friction force decreases with the decrease of graphene-substrate interaction strength (energy corrugation) is consistent with the MD simulations [ 16 ] and QCM experiment [ 17 ]. Fig.…”
Section: Resultssupporting
confidence: 87%
“…At the same time, some scholars have also been devoted to studying the friction of graphene and/or gold using other techniques. Quartz crystal microbalance (QCM) technique was employed to study the lubricity of gold on graphene [ 16 ] and the sliding friction of solid xenon film on graphene/Ni(111) substrate [ 17 ]. Both QCM experiments and molecular dynamics (MD) simulations show that the friction of an incommensurate Kr monolayer on Au follows a viscous friction law [ 18 , 19 ].…”
In this paper, we investigate the friction behaviors of graphene flakes sliding on a gold substrate using molecular dynamics simulations. The effects of flake size, flake shape, relative rotation angle between flake and substrate, and crystal orientation of substrate on the friction process are thoroughly studied. It is found that under the same load, the average friction forces per atom are smaller for a bigger graphene flake, which exhibits an obvious size effect. It is also shown that flake shape is critical in determining the friction in the sliding process. The average friction forces per atom for the square flake are much bigger than those for the triangular and round flakes. Moreover, the average friction forces per atom for the triangular flake are the smallest. We also find that the orientation of graphene flake relative to gold substrate plays a vital role in the friction process. The friction forces for the graphene flake sliding along the armchair direction are much bigger than those for the flakes with rotation. In addition, it is also found that single crystalline gold substrate exhibits a significant anisotropic effect of friction, which is attributed to the anisotropic effect of potential energy corrugation. These understandings not only shed light on the underlying mechanisms of graphene flake sliding on the gold substrates but also may guide the design and fabrication of nanoscale graphene-based devices.
“…It also reveals its inherent periodic character as argued in [2, 8], a physical fact being fully consistent with the proposed model. The method proposed for the experimental check-up is reminiscent of the (quartz) microbalance lubrication measurements, see [41]. For immersion in a suitable dynamic channeling context, one is encouraged to get in [43, 44].…”
Section: Super-biopolymer and Its Friction-lubrication/fl Propertiesmentioning
Articular cartilage is a natural tribochemical device just-designed by nature. Yet, a vivid debate goes on toward the mechanisms by which its nanoscopic viscoelastic properties facilitate lubrication in terms of ultralow static and kinetic friction coefficients. In this concisely conducted conceptual discussion, we wish to point out that a nanoscale tribomechanistic description based upon certain "viscoelastic quanta", called fractons, expressing spectral-mechanical properties of viscoelastic nets under the influence of force/pressure factor(s), may contribute substantially to the elucidation of ultralow coefficients of friction in the articular cartilage of predictable relaxational response. Our example unveils a part of a mechanically responsive viscoelastic network, such as a tied piece of hyaluronan molecule, fit in an Edwards type tube, in which upon water--mediated interaction of lipids with the hyaluronan when subjected to loading at the nanoscale, a consecutive stress-field and ion diffusion action is going to occur simultaneously. It results in a natural-logarithmic formula that interrelates a number of hyaluronan's interactive residues, N, with certain molecular-elastic (an exponent γ) and surface-to-volume (nano-colloid type) characteristics of around 2/3 to emerge near thermodynamic equilibrium, that is to say after a frictional loading action performed. It enables to relate uniquely a value of the exponent 0 < γ < 1/2 with a virtual tribomicellization scenario of the nanoscale friction--lubrication event accompanied by inevitable tubular-milieu viscosity alterations when the quasi-static friction scenario shows up, preferably with γ to 1/3 from above for large enough N–s. A periodic vibrational super-biopolymer's mode is exploited, leading to a change in the nanoscale friction-lubrication period from which an opportunity to involve an essential contribution to the (nanoscale) coefficient of friction arises.
“…The QCM is basically a piezoelectric sensor platform employing acoustic-electric effects that can measure mass resolution down to the picogram level 25 . By modifying the QCM chip sensing area with appropriate sensing layers (e.g., polymers 26–29 , metal oxides 30,31 , and some functional materials 32,33 ), specific analytes that are additionally deposited on its surface can induce a frequency shift, which can subsequently be translated into detected analyte mass according to the Sauerbrey equations 34 .…”
A novel, highly sensitive and selective safrole sensor has been developed using quartz crystal microbalance (QCM) coated with polyvinyl acetate (PVAc) nanofibers. The nanofibers were collected on the QCM sensing surface using an electrospinning method with an average diameter ranging from 612 nm to 698 nm and relatively high Q–factors (rigid coating). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the PVAc nanofiber surface morphology, confirming its high surface area and roughness, which are beneficial in improving the sensor sensitivity compared to its thin-film counterpart. The as-spun PVAc nanofiber sensor could demonstrate a safrole limit of detection (LOD) of down to 0.7 ppm with a response time of 171 s and a sensitivity of 1.866 Hz/ppm. It also showed good reproducibility, rapid response time, and excellent recovery. Moreover, cross-interference of the QCM sensor response to non-target gases was investigated, yielding very low cross-sensitivity and high selectivity of the safrole sensor. Owing to its high robustness and low fabrication cost, this proposed sensing device is expected to be a promising alternative to classical instrumental analytical methods for monitoring safrole-based drug precursors.
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