scholarly journals Surrogate Models for Studying the Wettability of Nanoscale Natural Rough Surfaces Using Molecular Dynamics

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2770
Author(s):  
Lingru Zheng ◽  
Maja Rücker ◽  
Tom Bultreys ◽  
Apostolos Georgiadis ◽  
Miranda M. Mooijer-van den Heuvel ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Contact Angle ◽  
Surrogate Model ◽  
Surface Topology ◽  
Coarse Grained ◽  
Modeling Methodology ◽  
Static Contact ◽  
Nanoscale Topography ◽  
Reconstructed Surface ◽  
Dynamics Simulations

A molecular modeling methodology is presented to analyze the wetting behavior of natural surfaces exhibiting roughness at the nanoscale. Using atomic force microscopy, the surface topology of a Ketton carbonate is measured with a nanometer resolution, and a mapped model is constructed with the aid of coarse-grained beads. A surrogate model is presented in which surfaces are represented by two-dimensional sinusoidal functions defined by both an amplitude and a wavelength. The wetting of the reconstructed surface by a fluid, obtained through equilibrium molecular dynamics simulations, is compared to that observed by the different realizations of the surrogate model. A least-squares fitting method is implemented to identify the apparent static contact angle, and the droplet curvature, relative to the effective plane of the solid surface. The apparent contact angle and curvature of the droplet are then used as wetting metrics. The nanoscale contact angle is seen to vary significantly with the surface roughness. In the particular case studied, a variation of over 65° is observed between the contact angle on a flat surface and on a highly spiked (Cassie–Baxter) limit. This work proposes a strategy for systematically studying the influence of nanoscale topography and, eventually, chemical heterogeneity on the wettability of surfaces.

Molecular Dynamics Analyses on Microscopic Contact Angle: Effect of Wall Atom Configuration

2006 ◽  
Author(s):  
Takahiro Ito ◽  
Yosuke Hirata ◽  
Yutaka Kukita
Keyword(s):  
Molecular Dynamics ◽  
Contact Angle ◽  
Dynamic Condition ◽  
Contact Angles ◽  
Numerical Density ◽  
Number Density ◽  
Subsequent Decrease ◽  
Static Contact ◽  
Dynamics Simulations ◽  
Atom Configuration

Boiling or condensing phenomena of liquid on the solid surface is greatly affected by the wetting condition of the liquid to the solid. Although the contact angle is one of the most important parameter to represent the wetting condition, the behavior of the contact angle is not understood well, especially in the dynamic condition. In this study we made molecular dynamics simulations to investigate the microscopic contact angle behavior under several conditions on the numerical density of the wall atoms. In the analyses, when the number density of the wall is lower, the changing rate of the dynamics contact angles for the variation of ΔV was higher than those for the case where the wall density is higher. This is mainly due to the crystallization of the fluid near the wall and subsequent decrease in the slip between the fluid and the wall. The analyses also show that the static contact angle decreases with increase in the number density of the wall. This was mainly induced by the increase in the number density of the wall itself.

scholarly journals Coarse-grained molecular models of the surface of hair

2021 ◽  
Author(s):  
Erik Weiand ◽  
James P. Ewen ◽  
Peter H. Koenig ◽  
Yuri Roiter ◽  
Steven H. Page ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Contact Angle ◽  
Molecular Dynamics Simulations ◽  
Molecular Model ◽  
Contact Angles ◽  
Coarse Grained ◽  
Lipid Monolayer ◽  
Sulfonate Group ◽  
Dynamics Simulations ◽  
Hair Surface

We present a coarse-grained molecular model of the surface of human hair, which consists of a lipid monolayer, in the MARTINI framework. Using molecular dynamics simulations, we identify a lipid grafting distance that yields a monolayer thickness consistent with atomistic simulations and experimental measurements of hair surfaces. Coarse-grained models for fully-functionalised, partially damaged, and fully damaged hair surfaces are created by randomly replacing neutral thioesters with anionic sulfonate groups. This mimics the progressive removal of fatty acids from the hair surface by bleaching. We study the structure of the lipid monolayer at different degrees of damage using molecular dynamics simulations in vacuum as well as in polar (water) and non-polar (n-hexadecane) solvents. We also compare the wetting behaviour of water and n-hexadecane on the hair surfaces through contact angle measurements conducted using molecular dynamics simulations and experiments. Our model captures the experimentally-observed transition of the hair surface from hydrophobic (and oleophilic) to hydrophilic (and oleophobic) as the level of bleaching damage increases. By using surfaces with different damage ratios, we obtain contact angles from the simulations that are in good agreement with experiments for both solvents on virgin and bleached human hairs. In both the molecular dynamics simulations and further experiments using biomimetic surfaces, the cosine of the water contact angle increases linearly with the sulfonate group surface coverage. We expect that the proposed systems will be useful for future molecular dynamics simulations of the adsorption and tribological behaviour of hair surfaces.

Parameterization of Divalent Cations for Coarse-Grained Simulations

2020 ◽  
Author(s):  
Florencia Klein ◽  
Daniela Cáceres-Rojas ◽  
Monica Carrasco ◽  
Juan Carlos Tapia ◽  
Julio Caballero ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Metal Ions ◽  
Molecular Dynamics Simulations ◽  
Divalent Cations ◽  
Computational Cost ◽  
Data Bank ◽  
Coarse Grained ◽  
Interaction Parameters ◽  
Dynamics Simulations ◽  
Dynamical Description

<p>Although molecular dynamics simulations allow for the study of interactions among virtually all biomolecular entities, metal ions still pose significant challenges to achieve an accurate structural and dynamical description of many biological assemblies. This is particularly the case for coarse-grained (CG) models. Although the reduced computational cost of CG methods often makes them the technique of choice for the study of large biomolecular systems, the parameterization of metal ions is still very crude or simply not available for the vast majority of CG- force fields. Here, we show that incorporating statistical data retrieved from the Protein Data Bank (PDB) to set specific Lennard-Jones interactions can produce structurally accurate CG molecular dynamics simulations. Using this simple approach, we provide a set of interaction parameters for Calcium, Magnesium, and Zinc ions, which cover more than 80% of the metal-bound structures reported on the PDB. Simulations performed using the SIRAH force field on several proteins and DNA systems show that using the present approach it is possible to obtain non-bonded interaction parameters that obviate the use of topological constraints. </p>

scholarly journals Variation of Interaction Zone Size For The Target Design of 2D Supramolecular Networks

2021 ◽  
Author(s):  
Łukasz Piotr Baran ◽  
Wojciech Rżysko ◽  
Dariusz Tarasewicz
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Self Assembly ◽  
The Self ◽  
Coarse Grained ◽  
Zone Size ◽  
Interaction Zone ◽  
Supramolecular Networks ◽  
Dynamics Simulations ◽  
Target Design

In this study we have performed extensive coarse-grained molecular dynamics simulations of the self-assembly of tetra-substituted molecules. We have found that such molecules are able to form a variety of...

Adsorption-induced co-assembly of hairy and isotropic particles

2020 ◽  
Vol 22 (16) ◽  
pp. 8757-8767
Author(s):  
Tomasz Staszewski ◽  
Małgorzata Borówko
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Coarse Grained ◽  
Dynamics Simulations ◽  
Coarse Grained Molecular Dynamics

We use coarse-grained molecular dynamics simulations to study the behavior of polymer-tethered particles immersed in fluids of isotropic particles.

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