Evaluation of Macroscale Wetting Equations on a Microrough Surface

Wang, Yan; Wang, Xiangdong; Du, Zhongjie; Zhang, Chen; Tian, Ming; Mi, Jianguo

doi:10.1021/la505035k

Cited by 10 publications

(5 citation statements)

References 41 publications

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“…Another important quantity to consider when dealing with nanoscale systems is the line tension . First defined by Gibbs, for a three phase system, the contact line tension is the excess free energy per unit length along the gas–solid interface .…”

Section: The Difference Of Nanomentioning

confidence: 99%

“…In these calculation, interatomic and intermolecular forces governed by Lennard‐Jones potential and the Hamaker theory are taken into account . Discrepancies between the contact angles predicted by macroscopic models and the actual contact angle measured on nanorough substrates was often attributed to significant line tension contribution . Recently Dietrich and co‐workers combined classical density functional theory to the string method and demonstrated that metastable states and deviation from the original theories arose from contact line pinning on nanodefects .…”

Section: Element Of Responsementioning

confidence: 99%

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Questions and Answers on the Wettability of Nano‐Engineered Surfaces

MacGregor

Vasilev

2017

Adv Materials Inter

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Surface roughening has long been used to confer materials remarkable wetting properties, such as super hydrophobicity. When roughness belongs to the microscale, existing models can, to some extent, explain and predict real‐world wetting states. With the advent of nanotechnology, however, a multitude of nano‐engineered materials are being developed and unexpected wetting behaviors have been observed which cannot be described by conventional theories. While it is clear that advanced nanotextured materials are essential to a vast range of ground breaking technologies, the intricate mechanisms governing the wetting of such surfaces—at the limit of validity of continuum theories—also need to be clarified. This review aims at presenting what is known and what remains to be discovered about the wettability of nanoengineered materials. The advantages and uniqueness of nanostructured substrates is highlighted first, with a focus on practical applications benefitting from the distinctive wetting properties of nanorough substrates. Classic wetting theories and their limitations are briefly discussed, before describing with a top down vision, why the wetting of nanostructured substrates differ from that of microtextured surfaces. Recent experimental and theoretical studies which contributed to the progress in this field are considered, before outlining potential future areas of research.

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Section: The Difference Of Nanomentioning

confidence: 99%

Section: Element Of Responsementioning

confidence: 99%

Questions and Answers on the Wettability of Nano‐Engineered Surfaces

MacGregor

Vasilev

2017

Adv Materials Inter

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“…The resulting energy barriers and critical radii were presented. In a subsequent work, line tensions, contact angles, and Tolman lengths were studied, and the effect of surface roughness on the wettability was investigated …”

Section: Introductionmentioning

confidence: 99%

“…In a subsequent work, line tensions, contact angles, and Tolman lengths were studied, 44 and the effect of surface roughness on the wettability was investigated. 45 The effect of surface roughness was also examined by Malijevsky, 46 who evaluated the prediction of Wenzel's law: that an increase of surface roughness leads to an increase in wettability of the fluid. The number of particles was constrained to a fixed value using a Lagrange multiplier, and the Helmholtz energy functional consists of an FMT 47,48 and a mean-field approach for the repulsive and attractive contributions, respectively.…”

Section: Introductionmentioning

confidence: 99%

Prediction of Contact Angles and Density Profiles of Sessile Droplets Using Classical Density Functional Theory Based on the PCP-SAFT Equation of State

et al. 2018

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This study demonstrates the capability of the density functional theory (DFT) formalism to predict contact angles and density profiles of model fluids and of real substances in good quantitative agreement with molecular simulations and experimental data. The DFT problem is written in cylindrical coordinates, and the solid−fluid interactions are defined as external potentials toward the fluid phase. Monte Carlo (MC) molecular simulations are conducted in order to assess the density profiles resulting from the Helmholtz energy functional used in the DFT formalism. Good quantitative agreement between DFT predictions and MC results for Lennard-Jones and ethane nanodroplets is observed, both for density profiles and for contact angles. That comparison suggests, first, that the Helmholtz energy functional proposed in a previous study [Sauer, E.; Gross, J. Ind. Eng. Chem. Res. 56, 2017, 4119−4135] is suitable for three-phase contact lines and, second, that Lagrange multipliers can be used to constrain the number of molecules, similar to a canonical ensemble. Experiments of sessile droplets on solid surfaces are performed to assess whether a real solid with its microscopic roughness can be described through a simple model potential. Comparison of DFT results to experimental data is done for a Teflon surface because Teflon can be regarded as a substrate exhibiting only attractive interactions of van der Waals type. It is shown that the real solid can be described as a perfectly planar solid with effective solvent-to-solid interactions, defined through a single adjustable parameter for the solid. Subsequent predictions for the contact angle of eight solvents, including polar components such as water, are found in very good agreement to experimental data using simple Berthelot−Lorentz combining rules. For the eight investigated solvents, we find mean absolute deviations of 3.77°.

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“…In the theoretical part, we attempted to interpret the hydrophobic mechanism of different rubber surfaces. Within the framework of our previously proposed three-dimensional density functional theory (3D-DFT), 24 the asymmetric interactions between particle and water molecules were described by the Hamaker theory, and the net and rough surfaces of SBR, polymethyl-vinylsiloxane (PMVS), and natural rubber (NR) were systematically investigated to decipher the effects of chemical and geometric characteristics on hydrophobicity and superhydrophobicity. According to surface morphologies and the interactions of rubber-water and particle−water, different droplet nucleation behaviors were considered to evaluate the contribution of the corner effect and line tension.…”

Section: Introductionmentioning

confidence: 99%

Macroscopic and Microscopic Analyses of Hydrophobic Modification of Rubbers with Silica Nanoparticles

Zhang

Tian

et al. 2015

J. Phys. Chem. C

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The wettability of rubbers with silica nanoparticle modification was investigated with theory and experiment. A simple coating technology was applied to generate the superhydrophobic styrene–butadiene rubber (SBR). Silica nanoparticles were covalently bonded with γ-methacryloxy propyl trimethoxysilane (γ-MPTMS), which was employed to improve coating durability through the thiol–ene click reaction with the SBR matrix. The contact angles of water droplets on the net and modified surfaces were then measured. The application of a three-dimensional density functional theory approach to predict the wetting contact angles showed that the chemical composition, chain conformation, and micro/nanostructure have different contributions to the hydrophobic behaviors. The theoretically predicted contact angles were partly validated by their experimental counterparts.

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Evaluation of Macroscale Wetting Equations on a Microrough Surface

Cited by 10 publications

References 41 publications

Questions and Answers on the Wettability of Nano‐Engineered Surfaces

Questions and Answers on the Wettability of Nano‐Engineered Surfaces

Prediction of Contact Angles and Density Profiles of Sessile Droplets Using Classical Density Functional Theory Based on the PCP-SAFT Equation of State

Macroscopic and Microscopic Analyses of Hydrophobic Modification of Rubbers with Silica Nanoparticles

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