Monte Carlo simulation strategies for computing the wetting properties of fluids at geometrically rough surfaces

Kumar, Vaibhaw; Sridhar, Shyam; Errington, Jeffrey R.

doi:10.1063/1.3655817

Cited by 46 publications

(49 citation statements)

References 69 publications

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“…Dewetting in hydrophobic confinement can also be important in a host of nonbiological phenomena, ranging from heterogeneous nucleation of vapor bubbles and contact line pinning, to the Cassie-Wenzel transitions on textured surfaces (60). These phenomena involve intricate confinement geometries, which could result in complex pathways involving one or more transitions between various dewetted morphologies, akin to the transition between isolated cavities and vapor tubes observed here.…”

Section: Discussion and Outlookmentioning

confidence: 99%

Pathways to dewetting in hydrophobic confinement

Remsing

Vembanur

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

107

136

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Liquid water can become metastable with respect to its vapor in hydrophobic confinement. The resulting dewetting transitions are often impeded by large kinetic barriers. According to macroscopic theory, such barriers arise from the free energy required to nucleate a critical vapor tube that spans the region between two hydrophobic surfaces-tubes with smaller radii collapse, whereas larger ones grow to dry the entire confined region. Using extensive molecular simulations of water between two nanoscopic hydrophobic surfaces, in conjunction with advanced sampling techniques, here we show that for intersurface separations that thermodynamically favor dewetting, the barrier to dewetting does not correspond to the formation of a (classical) critical vapor tube. Instead, it corresponds to an abrupt transition from an isolated cavity adjacent to one of the confining surfaces to a gap-spanning vapor tube that is already larger than the critical vapor tube anticipated by macroscopic theory. Correspondingly, the barrier to dewetting is also smaller than the classical expectation. We show that the peculiar nature of water density fluctuations adjacent to extended hydrophobic surfacesnamely, the enhanced likelihood of observing low-density fluctuations relative to Gaussian statistics-facilitates this nonclassical behavior. By stabilizing isolated cavities relative to vapor tubes, enhanced water density fluctuations thus stabilize novel pathways, which circumvent the classical barriers and offer diminished resistance to dewetting. Our results thus suggest a key role for fluctuations in speeding up the kinetics of numerous phenomena ranging from Cassie-Wenzel transitions on superhydrophobic surfaces, to hydrophobically driven biomolecular folding and assembly.capillary evaporation | fluctuations | kinetic barriers | assembly T he favorable interactions between two extended hydrophobic surfaces drive numerous biomolecular and colloidal assemblies (1-5), and have been the subject of several theoretical, computational, and experimental inquiries (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). Examples include the association of small proteins to form multimeric protein complexes, of amphiphlic block copolymers, dendrimers, or proteins to form vesicular suprastructures, and of patchy colloidal particles into complex crystalline lattices (23-27). When two such hydrophobic surfaces approach each other, water between them becomes metastable with respect to its vapor at a critical separation, d c , that can be quite large (8,9,(28)(29)(30). For nanometer-sized surfaces at ambient conditions, d c is proportional to the characteristic size of the hydrophobic object, whereas for micron-sized and larger surfaces, d c ∼ 1 μm (29, 30). However, due to the presence of large kinetic barriers separating the metastable wet and the stable dry states, the system persists in the wet state, and a dewetting transition is triggered only at much smaller separations (∼ 1 nm) (13,22,28,30).To uncover the mechanism of dewetting, a numbe...

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Section: Discussion and Outlookmentioning

confidence: 99%

Pathways to dewetting in hydrophobic confinement

Remsing

Vembanur

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

107

136

View full text Add to dashboard Cite

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“…As a result, most studies of adsorbed fluids resort to a plain truncation of fluid-fluid forces, without any attempt to correct for the missing interactions. [8][9][10][11][12][13][14][15][16][17][18] Already a while ago, Mansfield and Theodorou pointed out that truncating r −6 fluid-fluid interactions in systems where a z −3 fluid-wall potential is employed would have the effect of considerably favoring adhesive over cohesive interactions, and hence, very much affect the work of adhesion of adsorbed polymer films. 19,20 In order to remedy this problem, they developed a method for the calculation of tail corrections of adsorbed fluids.…”

Section: Introductionmentioning

confidence: 99%

Semi-infinite boundary conditions for the simulation of interfaces: The Ar/CO2(s) model revisited

Gregorio

Benet

Katcho

et al. 2012

The Journal of Chemical Physics

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We propose a method to account for the long tail corrections of dispersive forces in inhomogeneous systems. This method deals separately with the two interfaces that are usually present in a simulation setup, effectively establishing semi-infinite boundary conditions that are appropriate for the study of the interface between two infinite bulk phases. Using the wandering interface method, we calculate surface free energies of vapor-liquid, wall-liquid, and wall-vapor interfaces for a model of Lennard-Jones argon adsorbed on solid carbon dioxide. The results are employed as input to Young's equation, and the wetting temperature located. This estimate is compared with predictions from the method of effective interface potentials and good agreement is found. Our results show that truncating Ar-Ar interactions at two and a half molecular diameters results in a dramatic decrease of the wetting temperature of about 40%.

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“…For example, Koshi et al [64] applied an external force to visit both the wetting states and calculated the work done during the transition between the two states. Kumar et al [68] also demonstrated a method to evaluate the free energies of different wetting states for the Lennard-Jones system using the grand canonical Monte Carlo (GCMC) simulation. Further, Leroy and Muller-Plathe [69] developed a phantom wall method to create a path between specific wetting states and that of a droplet on a smooth surface.…”

Section: Water Droplet On Textured Surfacesmentioning

confidence: 98%

Understanding Wetting Transitions Using Molecular Simulation

Patra

Khan

Srivastava

et al. 2015

Springer Tracts in Mechanical Engineering

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The thermophysical and transport properties of fluid at nanoscale, adjacent to the solid surface, are quite different from that of macroscopic level. It has been realized that the fluid behavior can be tuned via modification of surfaces, which can unfold the underlying physics or mechanism of many biochemical processes or phenomena that exist in nature. In this chapter, we mainly emphasize the characteristic equilibrium properties of complex fluids near surfaces. In particular, we investigate different types of surface phase transitions such as layering transition, prewetting transition, and 2D vapor-liquid transition for associating (hydrogenbond-forming) fluids using molecular simulations. These phases can be altered or controlled using chemically modified surfaces to tune the structure and the stability of the adsorbed layers. In addition, the wetting behavior of different amphiphilic molecules such as water and ethanol and their mixture on smooth and rough surfaces is examined based on the contact angle of the liquid droplet on the surface. Different types of wetting modes such as Cassie-Baxter, Wenzel, and impregnation of a droplet are observed as a function of roughness factor, surface fraction, and composition of the binary mixture. The effect of electric field on the phase transition of water under nanoconfinement is also presented. Further, we also discuss the phase transition and transport properties of 2D thin films.

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Monte Carlo simulation strategies for computing the wetting properties of fluids at geometrically rough surfaces

Cited by 46 publications

References 69 publications

Pathways to dewetting in hydrophobic confinement

Pathways to dewetting in hydrophobic confinement

Semi-infinite boundary conditions for the simulation of interfaces: The Ar/CO2(s) model revisited

Understanding Wetting Transitions Using Molecular Simulation

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