TY - JOUR
T1 - Investigating Alkylsilane Monolayer Tribology at a Single-Asperity Contact with Molecular Dynamics Simulation
AU - Summers, Andrew Z.
AU - Iacovella, Christopher R.
AU - Cummings, Peter T.
AU - Mcabe, Clare
N1 - Funding Information:
The authors would like to acknowledge the National Science Foundation (NSF) for providing funding for this work through Grant ACI-1047827. Computational resources were provided by the National Energy Research Scientific Computing Center (NERSC), which is a DOE Office of Science User Facility support by the Office of Science of the U.S. Department of Energy under Contract DE-AC02-05CH11231.
Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/10/24
Y1 - 2017/10/24
N2 - Chemisorbed monolayer films are known to possess favorable characteristics for nanoscale lubrication of micro- and nanoelectromechanical systems (MEMS/NEMS). Prior studies have shown that the friction observed for monolayer-coated surfaces features a strong dependence on the geometry of contact. Specifically, tip-like geometries have been shown to penetrate into monolayer films, inducing defects in the monolayer chains and leading to plowing mechanisms during shear, which result in higher coefficients of friction (COF) than those observed for planar geometries. In this work, we use molecular dynamics simulations to examine the tribology of model silica single-asperity contacts under shear with monolayer-coated substrates featuring various film densities. It is observed that lower monolayer densities lead to reduced COFs, in contrast to results for planar systems where COF is found to be nearly independent of monolayer density. This is attributed to a liquid-like response to shear, whereby fewer defects are imparted in monolayer chains from the asperity, and chains are easily displaced by the tip as a result of the higher free volume. This transition in the mechanism of molecular plowing suggests that liquid-like films should provide favorable lubrication at single-asperity contacts.
AB - Chemisorbed monolayer films are known to possess favorable characteristics for nanoscale lubrication of micro- and nanoelectromechanical systems (MEMS/NEMS). Prior studies have shown that the friction observed for monolayer-coated surfaces features a strong dependence on the geometry of contact. Specifically, tip-like geometries have been shown to penetrate into monolayer films, inducing defects in the monolayer chains and leading to plowing mechanisms during shear, which result in higher coefficients of friction (COF) than those observed for planar geometries. In this work, we use molecular dynamics simulations to examine the tribology of model silica single-asperity contacts under shear with monolayer-coated substrates featuring various film densities. It is observed that lower monolayer densities lead to reduced COFs, in contrast to results for planar systems where COF is found to be nearly independent of monolayer density. This is attributed to a liquid-like response to shear, whereby fewer defects are imparted in monolayer chains from the asperity, and chains are easily displaced by the tip as a result of the higher free volume. This transition in the mechanism of molecular plowing suggests that liquid-like films should provide favorable lubrication at single-asperity contacts.
UR - http://www.scopus.com/inward/record.url?scp=85032023011&partnerID=8YFLogxK
U2 - 10.1021/acs.langmuir.7b02479
DO - 10.1021/acs.langmuir.7b02479
M3 - Article
C2 - 28915731
AN - SCOPUS:85032023011
SN - 0743-7463
VL - 33
SP - 11270
EP - 11280
JO - Langmuir
JF - Langmuir
IS - 42
ER -