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Yatsyshin P, Durán-Olivencia MA, Kalliadasis S. Microscopic aspects of wetting using classical density functional theory. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:274003. [PMID: 29786608 DOI: 10.1088/1361-648x/aac6fa] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Wetting is a rather efficient mechanism for nucleation of a phase (typically liquid) on the interface between two other phases (typically solid and gas). In many experimentally accessible cases of wetting, the interplay between the substrate structure, and the fluid-fluid and fluid-substrate intermolecular interactions brings about an entire 'zoo' of possible fluid configurations, such as liquid films with a thickness of a few nanometers, liquid nanodrops and liquid bridges. These fluid configurations are often associated with phase transitions occurring at the solid-gas interface and at lengths of just several molecular diameters away from the substrate. In this special issue article, we demonstrate how a fully microscopic classical density-functional framework can be applied to the efficient, rational and systematic exploration of the rich phase space of wetting phenomena. We consider a number of model prototype systems such as wetting on a planar wall, a chemically patterned wall and a wedge. Through density-functional computations we demonstrate that for these simply structured substrates the behaviour of the solid-gas interface is already highly complex and non-trivial.
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Affiliation(s)
- P Yatsyshin
- Department of Chemical Engineering, Imperial College London, London, SW7 2AZ, United Kingdom
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Yatsyshin P, Parry AO, Rascón C, Kalliadasis S. Wetting of a plane with a narrow solvophobic stripe. Mol Phys 2018. [DOI: 10.1080/00268976.2018.1473648] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Affiliation(s)
- P. Yatsyshin
- Department of Chemical Engineering, Imperial College London, London, UK
| | - A. O. Parry
- Department of Mathematics, Imperial College London, London, UK
| | - C. Rascón
- GISC, Universidad Carlos III de Madrid, Madrid, Spain
| | - S. Kalliadasis
- Department of Chemical Engineering, Imperial College London, London, UK
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Hu H, Chakraborty M, Allred TP, Weibel JA, Garimella SV. Multiscale Modeling of the Three-Dimensional Meniscus Shape of a Wetting Liquid Film on Micro-/Nanostructured Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:12028-12037. [PMID: 28953405 DOI: 10.1021/acs.langmuir.7b02837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The design of structured surfaces for increasing the heat flux dissipated during boiling and evaporation processes via enhanced liquid rewetting requires prediction of the liquid meniscus shape on these surfaces. In this study, a general continuum model is developed to predict the three-dimensional meniscus shape of liquid films on micro/nanostructured surfaces based on a minimization of the system free energy that includes solid-liquid van der Waals interaction energy, surface energy, and gravitational potential. The continuum model is validated at the nanoscale against molecular dynamics simulations of water films on gold surfaces with pyramidal indentations, and against experimental measurements of water films on silicon V-groove channels at the microscale. The validated model is used to investigate the effect of film thickness and surface structure depth on the meniscus shape. The meniscus is shown to become more conformal with the surface structure as the film thickness decreases and the structure depth increases. Assuming small interface slope and small variation in film thickness, the continuum model can be linearized to obtain an explicit expression for the meniscus shape. The error of this linearized model is quantitatively assessed and shown to increase with increasing structure depth and decreasing structure pitch. The model developed can be used for accurate prediction of three-dimensional meniscus shape on structured surfaces with micro/nano-scale features, which is necessary for determining the liquid delivery rate and heat flux dissipated during thin-film evaporation. The linearized model is useful for rapid prediction of meniscus shape when the structure depth is smaller than or comparable to the liquid film thickness.
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Affiliation(s)
- Han Hu
- School of Mechanical Engineering, Purdue University , West Lafayette, Indiana 47907, United States
| | - Monojit Chakraborty
- School of Mechanical Engineering, Purdue University , West Lafayette, Indiana 47907, United States
| | - Taylor P Allred
- School of Mechanical Engineering, Purdue University , West Lafayette, Indiana 47907, United States
| | - Justin A Weibel
- School of Mechanical Engineering, Purdue University , West Lafayette, Indiana 47907, United States
| | - Suresh V Garimella
- School of Mechanical Engineering, Purdue University , West Lafayette, Indiana 47907, United States
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Yatsyshin P, Parry AO, Rascón C, Kalliadasis S. Classical density functional study of wetting transitions on nanopatterned surfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:094001. [PMID: 28098073 DOI: 10.1088/1361-648x/aa4fd7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Even simple fluids on simple substrates can exhibit very rich surface phase behaviour. To illustrate this, we consider fluid adsorption on a planar wall chemically patterned with a deep stripe of a different material. In this system, two phase transitions compete: unbending and pre-wetting. Using microscopic density-functional theory, we show that, for thin stripes, the lines of these two phase transitions may merge, leading to a new two-dimensional-like wetting transition occurring along the walls. The influence of intermolecular forces and interfacial fluctuations on this phase transition and at complete pre-wetting are considered in detail.
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Affiliation(s)
- P Yatsyshin
- Department of Chemical Engineering, Imperial College London, London, SW7 2AZ, UK
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Silvestre NM, Telo da Gama MM, Tasinkevych M. Nematic films at chemically structured surfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:074002. [PMID: 28035088 DOI: 10.1088/1361-648x/aa4fd6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We investigate theoretically the morphology of a thin nematic film adsorbed at flat substrate patterned by stripes with alternating aligning properties, normal and tangential respectively. We construct a simple 'exactly-solvable' effective interfacial model where the liquid crystal distortions are accounted for via an effective interface potential. We find that chemically patterned substrates can strongly deform the nematic-air interface. The amplitude of this substrate-induced undulations increases with decreasing average film thickness and with increasing surface pattern pitch. We find a regime where the interfacial deformation may be described in terms of a material-independent universal scaling function. Surprisingly, the predictions of the effective interfacial model agree semi-quantitatively with the results of the numerical solution of a full model based on the Landau-de Gennes theory coupled to a square-gradient phase field free energy functional for a two phase system.
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Affiliation(s)
- N M Silvestre
- Centro de Física Teórica e Computacional, Departamento de Física, Faculdade de Ciências, Universidade de Lisboa, Campo Grande P-1749-016 Lisboa, Portugal
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Yatsyshin P, Parry AO, Kalliadasis S. Complete prewetting. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:275001. [PMID: 27214239 DOI: 10.1088/0953-8984/28/27/275001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We study continuous interfacial transitions, analagous to two-dimensional complete wetting, associated with the first-order prewetting line, which can occur on steps, patterned walls, grooves and wedges, and which are sensitive to both the range of the intermolecular forces and interfacial fluctuation effects. These transitions compete with wetting, filling and condensation producing very rich phase diagrams even for relatively simple prototypical geometries. Using microscopic classical density functional theory to model systems with realistic Lennard-Jones fluid-fluid and fluid-substrate intermolecular potentials, we compute mean-field fluid density profiles, adsorption isotherms and phase diagrams for a variety of confining geometries.
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Affiliation(s)
- P Yatsyshin
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK
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Honisch C, Lin TS, Heuer A, Thiele U, Gurevich SV. Instabilities of Layers of Deposited Molecules on Chemically Stripe Patterned Substrates: Ridges versus Drops. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:10618-10631. [PMID: 26339749 DOI: 10.1021/acs.langmuir.5b02407] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
A mesoscopic continuum model is employed to analyze the transport mechanisms and structure formation during the redistribution stage of deposition experiments where organic molecules are deposited on a solid substrate with periodic stripe-like wettability patterns. Transversally invariant ridges located on the more wettable stripes are identified as very important transient states and their linear stability is analyzed accompanied by direct numerical simulations of the fully nonlinear evolution equation for two-dimensional substrates. It is found that there exist two different instability modes that lead to different nonlinear evolutions that result (i) at large ridge volume in the formation of bulges that spill from the more wettable stripes onto the less wettable bare substrate and (ii) at small ridge volume in the formation of small droplets located on the more wettable stripes. In addition, the influence of different transport mechanisms during redistribution is investigated focusing on the cases of convective transport with no-slip at the substrate, transport via diffusion in the film bulk and via diffusion at the film surface. In particular, it is shown that the transport process does neither influence the linear stability thresholds nor the sequence of morphologies observed in the time simulation, but only the ratio of the time scales of the different process phases.
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Affiliation(s)
- Christoph Honisch
- Institute for Theoretical Physics, University of Münster , Wilhelm-Klemm-Str. 9, 48149 Münster, Germany
| | - Te-Sheng Lin
- Department of Applied Mathematics, National Chiao Tung University, Hsinchu , 30010 Taiwan
| | - Andreas Heuer
- Institute for Physical Chemistry, University of Münster , Correnstrasse 28/30, 48149 Münster, Germany
- Center of Nonlinear Science (CeNoS), University of Münster , Corrensstrasse 2, 48149 Münster, Germany
- Center for Multiscale Theory and Computation(CMTC), University of Münster , Corrensstrasse 40, 48149 Münster, Germany
| | - Uwe Thiele
- Institute for Theoretical Physics, University of Münster , Wilhelm-Klemm-Str. 9, 48149 Münster, Germany
- Center of Nonlinear Science (CeNoS), University of Münster , Corrensstrasse 2, 48149 Münster, Germany
- Center for Multiscale Theory and Computation(CMTC), University of Münster , Corrensstrasse 40, 48149 Münster, Germany
| | - Svetlana V Gurevich
- Institute for Theoretical Physics, University of Münster , Wilhelm-Klemm-Str. 9, 48149 Münster, Germany
- Center of Nonlinear Science (CeNoS), University of Münster , Corrensstrasse 2, 48149 Münster, Germany
- Center for Multiscale Theory and Computation(CMTC), University of Münster , Corrensstrasse 40, 48149 Münster, Germany
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Rodríguez-Rivas Á, Galván J, Romero-Enrique JM. Filling and wetting transitions on sinusoidal substrates: a mean-field study of the Landau-Ginzburg model. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:035101. [PMID: 25437528 DOI: 10.1088/0953-8984/27/3/035101] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We study the interfacial phenomenology of a fluid in contact with a one-dimensional array of infinitely long grooves of sinusoidal section, characterized by the periodicity length L and amplitude A. The system is modelled by the Landau-Ginzburg-Wilson functional, with fluid-substrate couplings which control the wettability of the substrate. We investigate the filling and wetting phenomena within the mean-field approximation, and compare with the predictions of the macroscopic and interfacial Hamiltonian theories. For large values of L and under bulk coexistence conditions, we observe first-order filling transitions between dry (D) and partially filled (F) interfacial states, and wetting transitions between partially filled F and completely wet (W) interfacial states of the same order as for the flat substrate. Depending on the order of the wetting transition, the transition temperature is either shifted towards lower temperatures for first-order wetting or it coincides with the wetting temperature on the flat substrate for continuous wetting. On the other hand, if the groove height is of order of the correlation length, only wetting transitions between D and W states are observed under bulk coexistence conditions. For this case, the transition temperature shift obeys approximately Wenzel's phenomenological law if the substrate favors first-order wetting, but it remains unshifted for continuous wetting. The borderline between the small and large L regimes correspond to a D - F - W triple point if wetting is first-order, and a D - F critical point for continuous wetting. Beyond bulk coexistence conditions, filling and first-order wetting transitions continue into off-coexistence filling and prewetting lines, which end up at critical points. Our findings show that the macroscopic theory only describes accurately the filling transition close to bulk coexistence and large L, while microscopic structure of the fluid is essential to understand wetting and filling away from bulk coexistence.
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Affiliation(s)
- Álvaro Rodríguez-Rivas
- Departamento de Física Atómica, Molecular y Nuclear, Area de Física Teórica, Universidad de Sevilla, Apartado de Correos 1065, 41080 Sevilla, Spain
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Chakraborty M, Ghosh UU, Chakraborty S, DasGupta S. Thermally enhanced self-propelled droplet motion on gradient surfaces. RSC Adv 2015. [DOI: 10.1039/c5ra00469a] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Enhanced droplet movement at elevated temperatures.
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Affiliation(s)
- Monojit Chakraborty
- Department of Chemical Engineering
- Indian Institute of Technology Kharagpur
- India
| | - Udita Uday Ghosh
- Department of Chemical Engineering
- Indian Institute of Technology Kharagpur
- India
| | - Suman Chakraborty
- Department of Mechanical Engineering
- Indian Institute of Technology Kharagpur
- India
| | - Sunando DasGupta
- Department of Chemical Engineering
- Indian Institute of Technology Kharagpur
- India
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Malijevský A. Complete wetting near an edge of a rectangular-shaped substrate. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:315002. [PMID: 24918632 DOI: 10.1088/0953-8984/26/31/315002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We consider fluid adsorption near a rectangular edge of a solid substrate that interacts with the fluid atoms via long range (dispersion) forces. The curved geometry of the liquid-vapour interface dictates that the local height of the interface above the edge ℓ(E) must remain finite at any subcritical temperature, even when a macroscopically thick film is formed far from the edge. Using an interfacial Hamiltonian theory and a more microscopic fundamental measure density functional theory (DFT), we study the complete wetting near a single edge and show that ℓ(E)(0)-ℓ(E)(δμ)∼δμ(β(CO)(E), as the chemical potential departure from the bulk coexistence δμ = μ(s)(T) - μ tends to zero. The exponent β(CO)(E) depends on the range of the molecular forces and in particular β(CO)(E)=2/3 for three-dimensional systems with van der Waals forces. We further show that for a substrate model that is characterised by a finite linear dimension L, the height of the interface deviates from the one at the infinite substrate as δℓE(L) ∼ L(-1) in the limit of large L. Both predictions are supported by numerical solutions of the DFT.
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Affiliation(s)
- Alexandr Malijevský
- Department of Physical Chemistry, Institute of Chemical Technology, Prague, 166 28 Praha 6, Czech Republic. Department of Aerosol Chemistry and Physics, ICPF, Academy of Sciences, 16502 Prague 6, Czech Republic
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Malijevský A. Filling and wetting transitions at grooved substrates. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:445006. [PMID: 24067670 DOI: 10.1088/0953-8984/25/44/445006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The wetting and filling properties of a fluid adsorbed on a solid grooved substrate are studied by means of a microscopic density functional theory. The grooved substrates are modelled using a solid slab, interacting with the fluid particles via long-range dispersion forces, to which a one-dimensional array of infinitely long rectangular grooves is sculpted. By investigating the effect of the groove periodicity and the width of the grooves and the ridges, a rich variety of different wetting morphologies is found. In particular, we show that for a saturated ambient gas, the adsorbent can occur in one of four wetting states characterized by (i) empty grooves, (ii) filled grooves, (iii) a formation of mesoscopic hemispherical caps (iv) a macroscopically wet surface. The character of the transition between particular regimes, that also extend off-coexistence, sensitively depends on the model geometry. The temperature at which the system becomes completely wet is considerably higher than that for a flat wall.
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Affiliation(s)
- Alexandr Malijevský
- E Hála Laboratory of Thermodynamics, Institute of Chemical Process Fundamentals, Academy of Sciences, 16502 Prague 6, Czech Republic. Department of Physical Chemistry, Institute of Chemical Technology, Prague, 166 28 Praha 6, Czech Republic
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Dörfler F, Rauscher M, Dietrich S. Stability of thin liquid films and sessile droplets under confinement. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 88:012402. [PMID: 23944464 DOI: 10.1103/physreve.88.012402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Indexed: 06/02/2023]
Abstract
The stability of nonvolatile thin liquid films and of sessile droplets is strongly affected by finite size effects. We analyze their stability within the framework of density functional theory using the sharp kink approximation, i.e., on the basis of an effective interface Hamiltonian. We show that finite size effects suppress spinodal dewetting of films because it is driven by a long-wavelength instability. Therefore nonvolatile films are stable if the substrate area is too small. Similarly, nonvolatile droplets connected to a wetting film become unstable if the substrate area is too large. This instability of a nonvolatile sessile droplet turns out to be equivalent to the instability of a volatile drop which can attain chemical equilibrium with its vapor.
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Affiliation(s)
- Fabian Dörfler
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, 70569 Stuttgart, Germany
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