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Sauer E, Terzis A, Theiss M, Weigand B, Gross J. Prediction of Contact Angles and Density Profiles of Sessile Droplets Using Classical Density Functional Theory Based on the PCP-SAFT Equation of State. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:12519-12531. [PMID: 30247038 DOI: 10.1021/acs.langmuir.8b01985] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
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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Affiliation(s)
- Elmar Sauer
- Institute of Thermodynamics and Thermal Process Engineering , University of Stuttgart , Pfaffenwaldring 9 , 70569 Stuttgart , Germany
| | - Alexandros Terzis
- Institute of Aerospace Thermodynamics , University of Stuttgart , Pfaffenwaldring 31 , 70569 Stuttgart , Germany
| | - Marc Theiss
- Institute of Thermodynamics and Thermal Process Engineering , University of Stuttgart , Pfaffenwaldring 9 , 70569 Stuttgart , Germany
| | - Bernhard Weigand
- Institute of Aerospace Thermodynamics , University of Stuttgart , Pfaffenwaldring 31 , 70569 Stuttgart , Germany
| | - Joachim Gross
- Institute of Thermodynamics and Thermal Process Engineering , University of Stuttgart , Pfaffenwaldring 9 , 70569 Stuttgart , Germany
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Liu Y, Zhang X. Vapor bridges between solid substrates in the presence of the contact line pinning effect: Stability and capillary force. J Chem Phys 2016; 145:214701. [DOI: 10.1063/1.4971207] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Yawei Liu
- State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, China
| | - Xianren Zhang
- State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, China
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Knežević M, Yeomans JM. Pore emptying transition during nucleation in hydrophobic nanopores. SOFT MATTER 2016; 12:3810-3819. [PMID: 26984813 DOI: 10.1039/c6sm00148c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Using the 2D Ising model we study the generic properties of nucleation in hydrophobic nanopores. To explore the pathways to nucleation of a spin-up phase from a metastable spin-down phase we perform umbrella sampling and transition path sampling simulations. We find that for narrow pores the nucleation occurs on the surface outside the pore. For wide pores the nucleation starts in the pore, and continues outside the filled pore. Intriguingly, we observe a pore emptying transition for a range of intermediate pore widths: a pre-critical nucleus fills the pore, continues to expand outside of the filled pore, but then suddenly gets expelled from the pore before reaching its critical size.
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Affiliation(s)
- Miloš Knežević
- The Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP, UK.
| | - Julia M Yeomans
- The Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP, UK.
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Imadate K, Hirahara K. In Situ Observation of Wetting Ionic Liquid on a Carbon Nanotube. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:2675-2678. [PMID: 26923157 DOI: 10.1021/acs.langmuir.5b04720] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The wetting behavior of an ionic liquid (IL) on individual carbon nanotubes (CNTs) was experimentally investigated using in situ electron microscopy. The tip of a single CNT was brought into contact with the surface of the IL using a nanomanipulator. The formation of a meniscus was observed immediately at the contact point. A thin layer of IL also formed simultaneously across the entire CNT surface. The force because of wetting was measured using the Wilhelmy method. After correcting the macroscale classical equations by considering an "apparent" diameter that corresponds well with the thickness of the IL layer on individual CNTs, the experimental data indicated that the wettability of single CNTs with diameters of over 10 nm was subjected to classical laws at the macroscale.
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Affiliation(s)
- Konan Imadate
- Department of Mechanical Engineering and ‡Center for Atomic and Molecular Technologies, Osaka University , 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Kaori Hirahara
- Department of Mechanical Engineering and ‡Center for Atomic and Molecular Technologies, Osaka University , 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
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Ye Y, Tian M, Zhang C, Du Z, Mi J. Understanding Controls on Wetting at Fluorinated Polyhedral Oligomeric Silsesquioxane/Polymer Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:230-238. [PMID: 26669413 DOI: 10.1021/acs.langmuir.5b02966] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Fluorinated polyhedral oligomeric silsesquioxane (F-POSS) nanoparticles have been widely used to enhance the hydrophobicity or oleophobicity of polymer films via constructing the specific micro/nanoscale roughness. In this work, we study the oleophobicity of pure and F-POSS-decorated poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) films using a dynamic density functional theory approach. The role of nanoparticle size and coverage and the chemical features of F-POSS and the polymer film in the wetting behavior of diiodomethane droplets has been integrated to the remaining ratio of surface potential to quantitatively characterize the corner effect. It is shown that, on the basis of universal force field parameters, the theoretically predicted contact angles are in general agreement with the available experimental data.
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Affiliation(s)
- Yi Ye
- State Key Laboratory of Organic-Inorganic Composites and ‡The Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology , Beijing 100029, China
| | - Ming Tian
- State Key Laboratory of Organic-Inorganic Composites and ‡The Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology , Beijing 100029, China
| | - Chen Zhang
- State Key Laboratory of Organic-Inorganic Composites and ‡The Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology , Beijing 100029, China
| | - Zhongjie Du
- State Key Laboratory of Organic-Inorganic Composites and ‡The Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology , Beijing 100029, China
| | - Jianguo Mi
- State Key Laboratory of Organic-Inorganic Composites and ‡The Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology , Beijing 100029, China
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Affiliation(s)
- J.A. van Meel
- FOM Institute for Atomic and Molecular Physics , Amsterdam, The Netherlands
| | - Y. Liu
- Department of Chemistry, University of Cambridge , Cambridge, UK
- State Key Laboratory of Organic–Inorganic Composites, Beijing University of Chemical Technology , Beijing, China
| | - D. Frenkel
- Department of Chemistry, University of Cambridge , Cambridge, UK
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Guo Z, Liu Y, Zhang X. Constrained lattice density functional theory and its applications on vapor–liquid nucleations. Sci Bull (Beijing) 2015. [DOI: 10.1007/s11434-014-0702-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Li J, Liu Y, Jiang G, Zhang X. Vapour-to-liquid nucleation in cone pores. MOLECULAR SIMULATION 2015. [DOI: 10.1080/08927022.2014.1001990] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Zhang Q, Sun D, Zhang Y, Zhu M. Lattice Boltzmann modeling of droplet condensation on superhydrophobic nanoarrays. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:12559-12569. [PMID: 25275954 DOI: 10.1021/la502641y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Droplet nucleation and growth on superhydrophobic nanoarrays is simulated by employing a multiphase, multicomponent lattice Boltzmann (LB) model. Three typical preferential nucleation modes of condensate droplets are observed through LB simulations with various geometrical parameters of nanoarrays, which are found to influence the wetting properties of nanostructured surfaces significantly. The droplets nucleated at the top of posts (top nucleation) or in the upside interpost space of nanoarrays (side nucleation) will generate a nonwetting Cassie state, while the ones nucleated at the bottom corners between the posts of nanoarrays (bottom nucleation) produce a wetting Wenzel state. The simulated time evolutions of droplet pressures at different locations are analyzed, which offers insight into the underlying physics governing the motion of droplets growing from different nucleation modes. It is demonstrated that the nanostructures with taller posts and a high ratio of post height to interpost space (H/S) are beneficial to produce the top- and side-nucleation modes. The simulated wetting states of condensate droplets on the nanostructures, having various geometrical configurations, compare reasonably well with experimental observations. The established relationship between the geometrical parameters of nanoarrays and the preferential nucleation modes of condensate droplets provides guidance for the design of nanoarrays with desirable anticondensation superhydrophobic properties.
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Affiliation(s)
- Qingyu Zhang
- Jiangsu Key Laboratory of Advanced Metallic Materials, School of Materials Science and Engineering, Southeast University , Nanjing 211189, People's Republic of China
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Li Y, Ren W. Numerical study of vapor condensation on patterned hydrophobic surfaces using the string method. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:9567-9576. [PMID: 25046586 DOI: 10.1021/la5020219] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Vapor condensation on solid surfaces plays a crucial role across a wide range of industrial applications. Recent advances of nanotechnology have made possible the manipulation of the condensation process through the control of surface structures. In this work, we study vapor condensation on hydrophobic surfaces patterned with microscale pillars. The critical nuclei, the activation barriers, and the minimum energy paths are computed using the climbing string method. The effects of pillar height, interpillar spacing, the level of supersaturation, and the intrinsic wettability of the solid surface on the nucleation process are investigated. Two nucleation scenarios are obtained from the computation. In the case of high pillar, narrow interpillar spacing, low supersaturation, and/or low surface wettability, the critical nucleus prefers the suspended Cassie state; otherwise, it prefers the impaled Wenzel state. A comparison of the nucleation barrier with that on a flat surface of the same material reveals that vapor condensation is inhibited by the microstructures in the former case, while enhanced in the latter case. The critical values of the pillar height, the interpillar spacing, and the supersaturation at which the critical nucleus changes from the Cassie state to the Wenzel state are identified from the phase diagram of the critical nucleus. It is found that the dependence of the critical interpillar spacing on the supersaturation follows closely the curve of the critical radii in a homogeneous nucleation. The relaxation dynamics of the condensate after the critical nucleus is formed is computed by solving the steepest descent equation. It is observed that when the pillar is low and/or the interpillar spacing is wide, a condensate initially in the Cassie state may evolve into the Wenzel state during the relaxation.
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Affiliation(s)
- Yunzhi Li
- Department of Mathematics, National University of Singapore , Singapore 119076
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