scholarly journals Scale-Dependent Friction-Coverage Relations and Non-Local Dissipation in Surfactant Monolayers

2020 ◽  
Author(s):  
Hongyu Gao ◽  
James Ewen ◽  
Remco Hartkamp ◽  
Martin H. Müser ◽  
Daniele Dini
Keyword(s):  
Surface Coverage ◽  
Leading Edge ◽  
Thermal Dissipation ◽  
Nonequilibrium Molecular Dynamics ◽  
Kinetic Friction ◽  
Surfactant Monolayers ◽  
Force Microscopy ◽  
Sliding Surfaces ◽  
Atomic Force ◽  
Afm Tips

<div>Surfactant molecules, known as organic friction modi?ers (OFMs), are added to lubricants to reduce friction and wear between sliding surfaces. In macroscale experiments, friction generally decreases as the coverage of OFM molecules on the sliding surfaces increases. However, recent nanoscale experiments with sharp atomic force microscopy (AFM) tips have shown increasing friction. To elucidate the origin of these opposite trends, we use nonequilibrium molecular dynamics (NEMD) simulations and study kinetic friction between OFM monolayers and an indenting nanoscale asperity. For this purpose, we study various coverages of stearamide OFMs on iron oxide surfaces and silica AFM tips with different radii of curvature. For our small tip radii, the friction coefficient and indentation depth both have a non-monotonic dependence on OFM surface coverage, with maxima occurring at intermediate coverage. This suggests that friction is dominated by plowing. We rationalise the non-monotonic relations through</div><div>a competition of two effects (confinement and packing density) that varying the surface coverage has on the effective stiffness of the OFM monolayers. We also show</div><div>that kinetic friction is not very sensitive to the sliding velocity in the range studied, indicating that it originates from instabilities. Indeed, while friction predominately</div><div>originates from the plowing action of the monolayers by the leading edge of the tip, thermal dissipation is mostly localised in molecules towards the trailing edge of the tip.</div>

scholarly journals Scale-Dependent Friction-Coverage Relations and Non-Local Dissipation in Surfactant Monolayers

2020 ◽  
Author(s):  
Hongyu Gao ◽  
James Ewen ◽  
Remco Hartkamp ◽  
Martin H. Müser ◽  
Daniele Dini
Keyword(s):  
Surface Coverage ◽  
Leading Edge ◽  
Thermal Dissipation ◽  
Nonequilibrium Molecular Dynamics ◽  
Kinetic Friction ◽  
Surfactant Monolayers ◽  
Force Microscopy ◽  
Sliding Surfaces ◽  
Atomic Force ◽  
Afm Tips

<div>Surfactant molecules, known as organic friction modifiers (OFMs), are added to lubricants to reduce friction and wear between sliding surfaces. In macroscale experiments, friction generally decreases as the coverage of OFM molecules on the sliding surfaces increases. However, recent nanoscale experiments with sharp atomic force microscopy (AFM) tips have shown increasing friction. To elucidate the origin of these opposite trends, we use nonequilibrium molecular dynamics (NEMD) simulations and study kinetic friction between OFM monolayers and an indenting nanoscale asperity. For this purpose, we study various coverages of stearamide OFMs on iron oxide surfaces and silica AFM tips with different radii of curvature. For our small tip radii, the friction coefficient and indentation depth both have a non-monotonic dependence on OFM surface coverage, with maxima occurring at intermediate coverage. This suggests that friction is dominated by plowing. We rationalise the non-monotonic relations through a competition of two effects (confinement and packing density) that varying the surface coverage has on the effective stiffness of the OFM monolayers. We also show that kinetic friction is not very sensitive to the sliding velocity in the range studied, indicating that it originates from instabilities. Indeed, while friction predominately originates from the plowing action of the monolayers by the leading edge of the tip, thermal dissipation is mostly localised in molecules towards the trailing edge of the tip.</div>

scholarly journals Scale-Dependent Friction-Coverage Relations and Non-Local Dissipation in Surfactant Monolayers

2021 ◽  
Author(s):  
Hongyu Gao ◽  
James Ewen ◽  
Remco Hartkamp ◽  
Martin H. Müser ◽  
Daniele Dini
Keyword(s):  
Surface Coverage ◽  
Leading Edge ◽  
Thermal Dissipation ◽  
Nonequilibrium Molecular Dynamics ◽  
Kinetic Friction ◽  
Surfactant Monolayers ◽  
Force Microscopy ◽  
Sliding Surfaces ◽  
Atomic Force ◽  
Afm Tips

Surfactant molecules, known as organic friction modifiers (OFMs), are routinely added to lubricants to reduce friction and wear between sliding surfaces. In macroscale experiments, friction generally decreases as the coverage of OFM molecules on the sliding surfaces increases; however, recent nanoscale experiments with sharp atomic force microscopy (AFM) tips have shown increasing friction. To elucidate the origin of these opposite trends, we use nonequilibrium molecular dynamics (NEMD) simulations and study kinetic friction between OFM monolayers and an indenting nanoscale asperity. For this purpose, we investigate various coverages of stearamide OFMs on iron oxide surfaces and silica AFM tips with different radii of curvature. We show that the differences between the friction-coverage relations from macroscale and nanoscale experiments are due to molecular plowing in the latter. For our small tip radii, the friction coefficient and indentation depth both have a non-monotonic dependence on OFM surface coverage, with maxima occurring at intermediate coverage. We rationalise the non-monotonic relations through a competition of two effects (confinement and packing density) that varying the surface coverage has on the effective stiffness of the OFM monolayers. We also show that kinetic friction is not very sensitive to the sliding velocity in the range studied, indicating that it originates from instabilities. Indeed, we find that friction predominately originates from plowing of the monolayers by the leading edge of the tip, where gauche defects are created, while thermal dissipation is mostly localised in molecules towards the trailing edge of the tip, where the chains return to a more extended conformation.<br>

scholarly journals Scale-Dependent Friction-Coverage Relations and Non-Local Dissipation in Surfactant Monolayers

2020 ◽  
Author(s):  
Hongyu Gao ◽  
James Ewen ◽  
Remco Hartkamp ◽  
Martin H. Müser ◽  
Daniele Dini
Keyword(s):  
Surface Coverage ◽  
Leading Edge ◽  
Thermal Dissipation ◽  
Nonequilibrium Molecular Dynamics ◽  
Kinetic Friction ◽  
Surfactant Monolayers ◽  
Force Microscopy ◽  
Sliding Surfaces ◽  
Atomic Force ◽  
Afm Tips

<div>Surfactant molecules, known as organic friction modi?ers (OFMs), are added to lubricants to reduce friction and wear between sliding surfaces. In macroscale experiments, friction generally decreases as the coverage of OFM molecules on the sliding surfaces increases. However, recent nanoscale experiments with sharp atomic force microscopy (AFM) tips have shown increasing friction. To elucidate the origin of these opposite trends, we use nonequilibrium molecular dynamics (NEMD) simulations and study kinetic friction between OFM monolayers and an indenting nanoscale asperity. For this purpose, we study various coverages of stearamide OFMs on iron oxide surfaces and silica AFM tips with different radii of curvature. For our small tip radii, the friction coefficient and indentation depth both have a non-monotonic dependence on OFM surface coverage, with maxima occurring at intermediate coverage. This suggests that friction is dominated by plowing. We rationalise the non-monotonic relations through</div><div>a competition of two effects (confinement and packing density) that varying the surface coverage has on the effective stiffness of the OFM monolayers. We also show</div><div>that kinetic friction is not very sensitive to the sliding velocity in the range studied, indicating that it originates from instabilities. Indeed, while friction predominately</div><div>originates from the plowing action of the monolayers by the leading edge of the tip, thermal dissipation is mostly localised in molecules towards the trailing edge of the tip.</div>

scholarly journals 3D-printed cellular tips for tuning fork atomic force microscopy in shear mode

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Liangdong Sun ◽  
Hongcheng Gu ◽  
Xiaojiang Liu ◽  
Haibin Ni ◽  
Qiwei Li ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Shear Mode ◽  
Unique Contribution ◽  
Force Microscopy ◽  
Atomic Force ◽  
Afm Tips ◽  
3D Printed ◽  
Architectured Material ◽  
Energy Absorbing ◽  
Absorption Field

AbstractConventional atomic force microscopy (AFM) tips have remained largely unchanged in nanomachining processes, constituent materials, and microstructural constructions for decades, which limits the measurement performance based on force-sensing feedbacks. In order to save the scanning images from distortions due to excessive mechanical interactions in the intermittent shear-mode contact between scanning tips and sample, we propose the application of controlled microstructural architectured material to construct AFM tips by exploiting material-related energy-absorbing behavior in response to the tip–sample impact, leading to visual promotions of imaging quality. Evidenced by numerical analysis of compressive responses and practical scanning tests on various samples, the essential scanning functionality and the unique contribution of the cellular buffer layer to imaging optimization are strongly proved. This approach opens new avenues towards the specific applications of cellular solids in the energy-absorption field and sheds light on novel AFM studies based on 3D-printed tips possessing exotic properties.

Probe-Tip Induced Damage in Compliant Substrates

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Michael Chandross ◽  
Christian D. Lorenz ◽  
Mark J. Stevens ◽  
Gary S. Grest
Keyword(s):  
Data Storage ◽  
Realistic Model ◽  
Experimental Measurements ◽  
Material Transfer ◽  
Force Microscopy ◽  
Compliant Substrates ◽  
Atomic Force ◽  
Low Load ◽  
Afm Tips ◽  
Dynamics Simulations

Nanofabrication using arrays of modified atomic force microscopy (AFM) tips can drastically reduce feature sizes and increase data storage densities. Additionally, AFM experiments are valuable tools for characterizing the tribological properties of surfaces. In order to maximize the potential of nanofabrication techniques, it is necessary to understand fully the interactions between AFM tips and substrates, particularly when the latter is compliant and more damage-prone. To address this issue, we have carried out extensive molecular dynamics simulations of the nanotribological properties of self-assembled alkylsilane monolayers (SAMs) on amorphous silica with a realistic model of an AFM tip. Our simulations demonstrate that for fully physisorbed SAMs, even low load contacts can damage the SAM and cause material transfer to the probe tip. This effect, which is commonly ignored, can have a strong effect on the interpretation of experimental measurements. Partial chemisorption of the SAM lowers, but does not remove the possibility of damage.

scholarly journals PREPARATION OF ODA-CLAY HYBRID FILMS BY LANGMUIR–BLODGETT TECHNIQUE

2009 ◽  
Vol 23 (10) ◽  
pp. 1351-1358 ◽  
Author(s):  
P. K. PAUL ◽  
S. A. HUSSAIN ◽  
D. BHATTACHARJEE
Keyword(s):  
Atomic Force Microscopy ◽  
Clay Minerals ◽  
Surface Pressure ◽  
Surface Coverage ◽  
Average Height ◽  
Hybrid Films ◽  
Force Microscopy ◽  
Langmuir Blodgett ◽  
Atomic Force ◽  
Pressure Area

Hybrid monolayers of clay minerals (hectorite) and Octadecyamine (ODA) were prepared using the Langmuir–Blodgett (LB) technique. Surface pressure–area per molecule isotherm, FTIR and atomic force microscopy were used to confirm and analyze the ODA-hectorite hybrid films. The monolayer thickness is 2 nm and average height, length and width of individual clay platelets ranges between 1.5 to 2 nm, 500 to 1250 nm and 100 to 115 nm respectively. The surface coverage was more than 80%.

Conductive-AFM for Scan Logic Failure Analysis at Advanced Technology Nodes

2016 ◽  
Author(s):  
Chuan Zhang ◽  
Oh Chong Khiam ◽  
Esther P.Y. Chen
Keyword(s):  
Failure Analysis ◽  
Failure Modes ◽  
Leading Edge ◽  
Advanced Technology ◽  
The Novel ◽  
Conductive Atomic Force Microscopy ◽  
Force Microscopy ◽  
Atomic Force ◽  
Technology Nodes ◽  
Process Structure

Abstract The increase in complexity of process, structure, and design not only increases the amount of failure analysis (FA) work significantly, but also leads to more complicated failure modes. To meet the need of high success rate and fast throughput FA operation at the leading-edge nodes, novel FA techniques have to be explored and incorporated into the routine FA flow. One of the novel techniques incorporated into the presented scan logic FA flow is the conductive-atomic force microscopy (CAFM) technique. This paper demonstrates CAFM technique as a powerful and efficient solution for scan logic failure analysis at advanced technology nodes. Several failure modes in scan logic FA are used as examples to illustrate how CAFM provides excellent solutions to some of the very challenging FA problems. The gate to active short in nFET devices, resistive contact, and open defect on gate contact are some modes used.

scholarly journals Thrombin-Binding Aptamer Quadruplex Formation: AFM and Voltammetric Characterization

2010 ◽  
Vol 2010 ◽  
pp. 1-8 ◽  
Author(s):  
Victor Constantin Diculescu ◽  
Ana-Maria Chiorcea-Paquim ◽  
Ramon Eritja ◽  
Ana Maria Oliveira-Brett
Keyword(s):  
Electron Transfer ◽  
Surface Coverage ◽  
Pyrolytic Graphite ◽  
Oxidation Potential ◽  
Oxidation Peak ◽  
No Adsorption ◽  
Guanine Oxidation ◽  
Force Microscopy ◽  
Atomic Force ◽  
Quadruplex Formation

The adsorption and the redox behaviour of thrombin-binding aptamer (TBA) and extended TBA (eTBA) were studied using atomic force microscopy and voltammetry at highly oriented pyrolytic graphite and glassy carbon. The different adsorption patterns and degree of surface coverage were correlated with the sequence base composition, presence/absence of K+, and voltammetric behaviour of TBA and eTBA. In the presence of K+, only a few single-stranded sequences present adsorption, while the majority of the molecules forms stable and rigid quadruplexes with no adsorption. Both TBA and eTBA are oxidized and the only anodic peak corresponds to guanine oxidation. Upon addition of K+ions, TBA and eTBA fold into a quadruplex, causing the decrease of guanine oxidation peak and occurrence of a new peak at a higher potential due to the oxidation of G-quartets. The higher oxidation potential of G-quartets is due to the greater difficulty of electron transfer from the inside of the quadruplex to the electrode surface than electron transfer from the more flexible single strands.

Nanotribology of Diamond Films Studied by Atomic Force Microscopy

1990 ◽  
Vol 188 ◽  
Author(s):  
Gabi Neubauer ◽  
Sidney R. Cohen ◽  
Gary M. Mcclelland ◽  
Hajime Seki
Keyword(s):  
High Vacuum ◽  
Diamond Films ◽  
Ultra High Vacuum ◽  
Nanometer Scale ◽  
Kinetic Friction ◽  
Experimental Conditions ◽  
Stick Slip ◽  
Force Microscopy ◽  
Atomic Force ◽  
The Difference

ABSTRACTAn atomic force microscope, operated in ultra-high vacuum has been employed to study the tribological properties of diamond films under small loads (< 10−6 N) on a nanometer scale. The incidence of intermittent motion, “stick-slip”, while sliding a diamond tip across the diamond film, is detected under certain experimental conditions and is discussed with respect to the difference between static and kinetic friction, sample topography and a varying sample condition.

Immobilization of oligonucleotide-functionalized magnetic nanobeads in DNA-coils studied by electron microscopy and atomic force microscopy

2011 ◽  
Vol 1355 ◽  
Author(s):  
Mattias Strömberg ◽  
Sultan Akhtar ◽  
Klas Gunnarsson ◽  
Camilla Russell ◽  
David Herthnek ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Atomic Force Microscopy ◽  
Surface Coverage ◽  
Rolling Circle Amplification ◽  
High Surface ◽  
Rolling Circle ◽  
Force Microscopy ◽  
Atomic Force ◽  
Immobilized Beads ◽  
Magnetic Nanobeads

ABSTRACTImmobilization of oligonucleotide-functionalized magnetic nanobeads by hybridization in DNA-coils formed by rolling circle amplification has been investigated using transmission electron microscopy (TEM) and atomic force microscopy (AFM). The TEM results supported earlier made observations that small beads with low oligonucleotide surface coverage preferably immobilize in the interior of the DNA-coils and do not tend to link several DNA-coils together whereas large beads with high surface coverage to a larger extent connect several DNA-coils together to clusters of several DNA-coils with beads. AFM provided direct visualization of the DNA-coils as thread-like objects. DNA-coils with immobilized beads appeared as a collection of beads with thread-like features in their near vicinity.

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