Simulation of Water Flow in a Coated Nano Pore by a Molecular Dynamics

2008 ◽  
Vol 57 ◽  
pp. 73-79
Author(s):  
K. Yamamoto ◽  
T. Iwatsubo ◽  
Ken-ichi Saitoh ◽  
T. Moriuchi
Keyword(s):  
Molecular Dynamics ◽  
Contact Angle ◽  
Silica Gel ◽  
Contact Angles ◽  
Dissipation Energy ◽  
Water Flows ◽  
Piston Cylinder ◽  
Pore Length ◽  
Spherical Silica ◽  
Extension Force

This paper presents on a new damping element called the colloidal damper which is used a principle of surface extension force in nano pore. The direction acting of the surface extension force of water in hydrophobic nano pore is different in pressurization and decompressurization processes [1,2]. This principle is applied to a damping element. The nano pore is constructed by silica gel. A silica gel ball of 100-200 micrometer dia. has many nano pores of 5-20 nanometer dia. in it [3,4]. The coated spherical silica gel and water are inserted in a piston - cylinder unit in order to work as a damper. If compression and decompression forces are added to the piston - cylinder unit (damper), water flows into and moves out the nano pore under balance of pressure. A contact angle of compression formed by the hydrophobic nano pore and water is larger than that of decompression. This difference of the contact angle produces a damping energy. In this paper, behavior of water in the pore of silica gel is investigated using the molecular dynamics. Dissipation energy of the colloidal damper is concerned with the contact angles of water in the pore. So the contact angles are calculated for changing parameters, i.e. size of the pore, length of the hydrophobic material, velocity (pressure) of water flows into the pore. Then these results are compared with the experimental ones.

scholarly journals Molecular Dynamics Simulation of Wetting Behavior: Contact Angle Dependency on Water Potential Models

2021 ◽  
Vol 1 (1) ◽  
pp. 10
Author(s):  
Lukman Hakim ◽  
Irsandi Dwi Oka Kurniawan ◽  
Ellya Indahyanti ◽  
Irwansyah Putra Pradana
Keyword(s):  
Molecular Dynamics ◽  
Contact Angle ◽  
Liquid Droplet ◽  
Center Of Mass ◽  
Contact Angles ◽  
Surface Wettability ◽  
Dynamics Simulation ◽  
Potential Models ◽  
Surface Hydrophilicity ◽  
Dynamics Simulations

The underlying principle of surface wettability has obtained great attentions for the development of novel functional surfaces. Molecular dynamics simulations has been widely utilized to obtain molecular-level details of surface wettability that is commonly quantified in term of contact angle of a liquid droplet on the surface. In this work, the sensitivity of contact angle calculation at various degrees of surface hydrophilicity to the adopted potential models of water: SPC/E, TIP4P, and TIP5P, is investigated. The simulation cell consists of a water droplet on a structureless surface whose hydrophilicity is modified by introducing a scaling factor to the water-surface interaction parameter. The simulation shows that the differences in contact angle described by the potential models are systematic and become more visible with the increase of the surface hydrophilicity. An alternative method to compute a contact angle based on the height of center-of-mass of the droplet is also evaluated, and the resulting contact angles are generally larger than those determined from the liquid-gas interfacial line.

scholarly journals Contact angle and adsorption energies of nanoparticles at the air–liquid interface determined by neutron reflectivity and molecular dynamics

Nanoscale ◽  
2015 ◽  
Vol 7 (13) ◽  
pp. 5665-5673 ◽  
Author(s):  
Javier Reguera ◽  
Evgeniy Ponomarev ◽  
Thomas Geue ◽  
Francesco Stellacci ◽  
Fernando Bresme ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Contact Angle ◽  
Contact Angles ◽  
Liquid Interface ◽  
Neutron Reflectivity ◽  
New Approach ◽  
Adsorption Energies ◽  
Air Liquid Interface

A new approach, based on in situ neutron reflectivity and molecular dynamics has been developed for calculating contact angles of nanoparticles at interfaces.

Molecular Dynamics Simulation of Ultra-Fast Phase Transition in Water Nanofilms

2020 ◽  
Author(s):  
Malcolm Porterfield ◽  
Diana Borca-Tasciuc
Keyword(s):  
Molecular Dynamics ◽  
Contact Angle ◽  
Morse Potential ◽  
Water Film ◽  
Contact Angles ◽  
Gold Substrate ◽  
Explosive Boiling ◽  
Interaction Sites ◽  
Lennard Jones ◽  
Water Films

Abstract Molecular dynamics simulations are used to explore explosive boiling of thin water films on a gold substrate. In particular, water films of 2.5, 1.6 and 0.7 nanometer thickness were examined. Three different surface wettabilities with contact angles of 11, 47 and 110 degrees were simulated along with substrate temperatures of 400K, 600K, 800K and 1000K. The 11 degree contact angle was obtained using a Morse interaction potential between the water film and the gold substrate while the 47 and 110 degree contact angles were obtained via a Lennard-Jones potential. Evaporation was the first mode of phase change observed in all cases and explosive boiling did not occur until the substrate reached a temperature of 800K. When explosive boiling was present for all three contact angles, it was consistently shown to occur first for the surface with a 47 degree contact angle, contrary to the expectation that it would occur first on the substrate with an 11 degree contact angle. These results suggest that explosive boiling onset is strongly dependent on the particularities of the interaction potential. For instance, the Morse potential used to model the surface described by an 11 degree contact angle, is a softer potential as compared with Lennard-Jones, but has more interaction sites per molecule — two hydrogen atoms and one oxygen atom vs one oxygen atom. Thus, although the water film reaches a higher temperature with the Morse potential, explosive boiling onset is delayed as more interaction sites have to be disrupted. These results suggest that both the interaction strength and the number of atoms interacting at the interface must be considered when investigating trends of explosive boiling with surface wettability.

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.

A GEOCHEMISTRY-ORIENTED WORKFLOW FOR WETTABILITY ASSESSMENT AT RESERVOIR CONDITION USING MOLECULAR DYNAMICS SIMULATIONS

2021 ◽  
Author(s):  
Isa Silveira de Araujo ◽  
◽  
Archana Jagadisan ◽  
Zoya Heidari ◽  
◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Contact Angle ◽  
Molecular Dynamics Simulations ◽  
Water Droplet ◽  
Contact Angles ◽  
Fluid Distribution ◽  
Reservoir Temperature ◽  
Reservoir Condition ◽  
Dynamics Simulations ◽  
The Impact

Reliable quantification of wettability is critical in assessment of fluid distribution, capillary pressure, relative permeability, and flow properties of fluids in reservoirs. Wettability of reservoirs can be affected by chemical composition of rock-fluid system, salinity, and reservoir temperature. Experimental assessment of wettability under reservoir conditions, while gaining control on the aforementioned parameters, may be tedious and challenging. Several published researches have used experimental studies to focus on determining the impact of individual factors on wettability of rock. However, studies on the combined effects of these factors are limited, although critical, for better understanding of wettability of hydrocarbon reservoirs. In this paper we introduce a workflow for assessment of wettability of rocks at reservoir condition using molecular dynamics (MD) simulations. The outcomes include (i) quantifying the wettability of pure minerals, (ii) quantifying the impact of reservoir temperature on wettability of pure mineral. The inputs to the simulation include molecules of pure minerals (quartz, calcite, albite) packed in a cubical simulation box. The molecules are condensed to form a flat surface. Subsequently, water and oil (hexane) molecules are placed on the surface of the mineral. We then perform simulations with constant number of particles, temperature and volume (NVT) on the system till equilibrium is reached. At equilibrium, the contact angle formed by the water droplet is measured. Contact angle is simulated for temperature conditions in the range of 300 to 380 K. The results showed that the contact angle between water-mineral for quartz, calcite, and albite at room temperature (300 K) ranges from 30º to 45º, indicating that the surface of these minerals is hydrophilic, with different degrees of hydrophilicity. This information is essential for reliable fluid flow simulations, which are often overlooked in conventional approaches. We also found that the temperature has a measurable impact on the contact angles formed by water droplet. We found that increase in temperature from 300 to 380 K decreases the contact angles by approximately 30% on quartz surfaces, 20% on albite surfaces, and 24% on calcite surfaces. The results for the hexane-mineral system show that the hexane behaved similarly in the three minerals surface. A thin film of hexane is formed at the surface corresponding to a contact angle of 0º. The method introduced in this paper has application for reliable evaluation of wettability at any reservoir of interest by knowing the molecular structure of clay and non-clay minerals as well as fluid content. Moreover, the challenges of wettability determination under high temperature and pressure conditions can also be efficiently addressed by using molecular dynamics simulations.

scholarly journals Influence of moisture content on the contact angle and surface tension measured on birch wood surfaces

2021 ◽  
Author(s):  
Rami Benkreif ◽  
Fatima Zohra Brahmia ◽  
Csilla Csiha
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Moisture Content ◽  
Solid Wood ◽  
Contact Angles ◽  
Surface Moisture ◽  
Wood Coatings ◽  
The Relationship ◽  
Wood Surfaces

AbstractSurface tension of solid wood surfaces affects the wettability and thus the adhesion of various adhesives and wood coatings. By measuring the contact angle of the wood, the surface tension can be calculated based on the Young-Dupré equation. Several publications have reported on contact angle measured with different test liquids, under different conditions. Results can only be compared if the test conditions are similar. While the roles of the drop volume, image shooting time etc., are widely recognized, the role of the wood surface moisture content (MC) is not evaluated in detail. In this study, the effect of wood moisture content on contact angle values, measured with distilled water and diiodomethane, on sanded birch (Betula pendula) surfaces was investigated, in order to find the relationship between them. With increasing MC from approximately 6% to 30%, increasing contact angle (decreasing surface tension) values were measured according to a logarithmic function. The function makes possible the calculation of contact angles that correspond to different MCs.

scholarly journals Biomimetic Approach for the Elaboration of Highly Hydrophobic Surfaces: Study of the Links between Morphology and Wettability

Biomimetics ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 38
Author(s):  
Quentin Legrand ◽  
Stephane Benayoun ◽  
Stephane Valette
Keyword(s):  
Contact Angle ◽  
Ginkgo Biloba ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Textured Surfaces ◽  
Replication Process ◽  
Wetting Behavior ◽  
Static Contact ◽  
Biomimetic Approach ◽  
Highly Hydrophobic

This investigation of morphology-wetting links was performed using a biomimetic approach. Three natural leaves’ surfaces were studied: two bamboo varieties and Ginkgo Biloba. Multiscale surface topographies were analyzed by SEM observations, FFT, and Gaussian filtering. A PDMS replicating protocol of natural surfaces was proposed in order to study the purely morphological contribution to wetting. High static contact angles, close to 135∘, were measured on PDMS replicated surfaces. Compared to flat PDMS, the increase in static contact angle due to purely morphological contribution was around 20∘. Such an increase in contact angle was obtained despite loss of the nanometric scale during the replication process. Moreover, a significant decrease of the hysteresis contact angle was measured on PDMS replicas. The value of the contact angle hysteresis moved from 40∘ for flat PDMS to less than 10∘ for textured replicated surfaces. The wetting behavior of multiscale textured surfaces was then studied in the frame of the Wenzel and Cassie–Baxter models. Whereas the classical laws made it possible to describe the wetting behavior of the ginkgo biloba replications, a hierarchical model was developed to depict the wetting behavior of both bamboo species.

scholarly journals Is contact angle a cause or an effect? – A cautionary tale

2020 ◽  
Vol 146 ◽  
pp. 03004
Author(s):  
Douglas Ruth
Keyword(s):  
Contact Angle ◽  
Solid Surface ◽  
Contact Angles ◽  
Two Dimensions ◽  
Experimental Results ◽  
Flow In Porous Media ◽  
Two Dimensional ◽  
Wide Range ◽  
Fluid Drop ◽  
Surrounding Fluid

The most influential parameter on the behavior of two-component flow in porous media is “wettability”. When wettability is being characterized, the most frequently used parameter is the “contact angle”. When a fluid-drop is placed on a solid surface, in the presence of a second, surrounding fluid, the fluid-fluid surface contacts the solid-surface at an angle that is typically measured through the fluid-drop. If this angle is less than 90°, the fluid in the drop is said to “wet” the surface. If this angle is greater than 90°, the surrounding fluid is said to “wet” the surface. This definition is universally accepted and appears to be scientifically justifiable, at least for a static situation where the solid surface is horizontal. Recently, this concept has been extended to characterize wettability in non-static situations using high-resolution, two-dimensional digital images of multi-component systems. Using simple thought experiments and published experimental results, many of them decades old, it will be demonstrated that contact angles are not primary parameters – their values depend on many other parameters. Using these arguments, it will be demonstrated that contact angles are not the cause of wettability behavior but the effect of wettability behavior and other parameters. The result of this is that the contact angle cannot be used as a primary indicator of wettability except in very restricted situations. Furthermore, it will be demonstrated that even for the simple case of a capillary interface in a vertical tube, attempting to use simply a two-dimensional image to determine the contact angle can result in a wide range of measured values. This observation is consistent with some published experimental results. It follows that contact angles measured in two-dimensions cannot be trusted to provide accurate values and these values should not be used to characterize the wettability of the system.

scholarly journals Fabrication of elastic, conductive, wear-resistant superhydrophobic composite material

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Seyed Mehran Mirmohammadi ◽  
Sasha Hoshian ◽  
Ville P. Jokinen ◽  
Sami Franssila
Keyword(s):  
Contact Angle ◽  
Composite Material ◽  
Contact Angles ◽  
Wet Etching ◽  
Sliding Angle ◽  
Electrically Conductive ◽  
Wear Resistant ◽  
Nanoscale Structures ◽  
Mechanical Abrasion ◽  
Mechanical Durability

AbstractA polydimethylsiloxane (PDMS)/Cu superhydrophobic composite material is fabricated by wet etching, electroless plating, and polymer casting. The surface topography of the material emerges from hierarchical micro/nanoscale structures of etched aluminum, which are rigorously copied by plated copper. The resulting material is superhydrophobic (contact angle > 170°, sliding angle < 7° with 7 µL droplets), electrically conductive, elastic and wear resistant. The mechanical durability of both the superhydrophobicity and the metallic conductivity are the key advantages of this material. The material is robust against mechanical abrasion (1000 cycles): the contact angles were only marginally lowered, the sliding angles remained below 10°, and the material retained its superhydrophobicity. The resistivity varied from 0.7 × 10–5 Ωm (virgin) to 5 × 10–5 Ωm (1000 abrasion cycles) and 30 × 10–5 Ωm (3000 abrasion cycles). The material also underwent 10,000 cycles of stretching and bending, which led to only minor changes in superhydrophobicity and the resistivity remained below 90 × 10–5 Ωm.

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