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Davis D, Gupta BS. Surface-directed spinodal decomposition of fluids confined in a cylindrical pore. Phys Rev E 2023; 108:064607. [PMID: 38243488 DOI: 10.1103/physreve.108.064607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 11/21/2023] [Indexed: 01/21/2024]
Abstract
The surface-directed spinodal decomposition of a binary liquid confined inside a cylindrical pore is investigated using molecular dynamics simulations. One component of the liquid wets the pore surface while the other remains neutral. A variety of wetting conditions are studied. For the partial wetting case, after an initial period of phase separation, the domains organize themselves into pluglike structures and the system enters into a metastable state. Therefore, a complete phase separation is never achieved. Analysis of domain growth and the structure factor suggests a one-dimensional growth dynamics for the partial wetting case. As the wetting interaction is increased beyond a critical value, a transition from the pluglike to tubelike domain formation is observed, which corresponds to the full wetting morphology. Thus, a complete phase separation is achieved as the wetting species moves towards the pore surface and forms layers enclosing the nonwetting species residing around the axis of the cylinder. The coarsening dynamics of both the species are studied separately. The wetting species is found to follow a two-dimensional domain growth dynamics with a growth exponent 1/2 in the viscous hydrodynamic regime. This was substantiated by the Porod tail of the structure factor. On the other hand, the domain grows linearly with time for the nonwetting species. This suggests that the nonwetting species behaves akin to a three-dimensional bulk system. An appropriate reasoning is presented to justify the given observations.
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Affiliation(s)
- Daniya Davis
- Department of Physics, School of Advanced Sciences, Vellore Institute of Technology, Vellore, Tamil Nadu 632014, India
| | - Bhaskar Sen Gupta
- Department of Physics, School of Advanced Sciences, Vellore Institute of Technology, Vellore, Tamil Nadu 632014, India
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2
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Shao PW, Wu YX, Chen WH, Zhang M, Dai M, Kuo YC, Hsieh SH, Tang YC, Liu PL, Yu P, Chen Y, Huang R, Chen CH, Hsu JH, Chen YC, Hu JM, Chu YH. Bicontinuous oxide heteroepitaxy with enhanced photoconductivity. Nat Commun 2023; 14:21. [PMID: 36596763 PMCID: PMC9810741 DOI: 10.1038/s41467-022-35385-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Accepted: 11/29/2022] [Indexed: 01/04/2023] Open
Abstract
Self-assembled systems have recently attracted extensive attention because they can display a wide range of phase morphologies in nanocomposites, providing a new arena to explore novel phenomena. Among these morphologies, a bicontinuous structure is highly desirable based on its high interface-to-volume ratio and 3D interconnectivity. A bicontinuous nickel oxide (NiO) and tin dioxide (SnO2) heteroepitaxial nanocomposite is revealed here. By controlling their concentration, we fabricated tuneable self-assembled nanostructures from pillars to bicontinuous structures, as evidenced by TEM-energy-dispersive X-ray spectroscopy with a tortuous compositional distribution. The experimentally observed growth modes are consistent with predictions by first-principles calculations. Phase-field simulations are performed to understand 3D microstructure formation and extract key thermodynamic parameters for predicting microstructure morphologies in SnO2:NiO nanocomposites of other concentrations. Furthermore, we demonstrate significantly enhanced photovoltaic properties in a bicontinuous SnO2:NiO nanocomposite macroscopically and microscopically. This research shows a pathway to developing innovative solar cell and photodetector devices based on self-assembled oxides.
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Affiliation(s)
- Pao-Wen Shao
- grid.260539.b0000 0001 2059 7017Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu, 30010 Taiwan
| | - Yi-Xian Wu
- grid.260539.b0000 0001 2059 7017Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu, 30010 Taiwan
| | - Wei-Han Chen
- grid.260539.b0000 0001 2059 7017Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu, 30010 Taiwan
| | - Mojue Zhang
- grid.14003.360000 0001 2167 3675Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706 USA
| | - Minyi Dai
- grid.14003.360000 0001 2167 3675Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706 USA
| | - Yen-Chien Kuo
- grid.410766.20000 0001 0749 1496National Synchrotron Radiation Research Center, Hsinchu, 30076 Taiwan
| | - Shang-Hsien Hsieh
- grid.410766.20000 0001 0749 1496National Synchrotron Radiation Research Center, Hsinchu, 30076 Taiwan
| | - Yi-Cheng Tang
- grid.260542.70000 0004 0532 3749Graduate Institute of Precision Engineering, National Chung Hsing University, Taichung, 402 Taiwan
| | - Po-Liang Liu
- grid.260542.70000 0004 0532 3749Graduate Institute of Precision Engineering, National Chung Hsing University, Taichung, 402 Taiwan
| | - Pu Yu
- grid.12527.330000 0001 0662 3178State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, 100084 Beijing, People’s Republic of China
| | - Yuang Chen
- grid.22069.3f0000 0004 0369 6365Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, 200241 Shanghai, China
| | - Rong Huang
- grid.22069.3f0000 0004 0369 6365Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, 200241 Shanghai, China
| | - Chia-Hao Chen
- grid.410766.20000 0001 0749 1496National Synchrotron Radiation Research Center, Hsinchu, 30076 Taiwan
| | - Ju-Hung Hsu
- Integrated Service Technology, Hsinchu, Taiwan
| | - Yi-Chun Chen
- grid.64523.360000 0004 0532 3255Department of Physics, National Cheng Kung University, Tainan, 70101 Taiwan
| | - Jia-Mian Hu
- grid.14003.360000 0001 2167 3675Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706 USA
| | - Ying-Hao Chu
- grid.260539.b0000 0001 2059 7017Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu, 30010 Taiwan ,grid.38348.340000 0004 0532 0580Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, 30013 Taiwan
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Zaidi SSH, Jaiswal PK, Priya M, Puri S. Universal fast mode regime in wetting kinetics. Phys Rev E 2022; 106:L052801. [PMID: 36559410 DOI: 10.1103/physreve.106.l052801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 10/02/2022] [Indexed: 06/17/2023]
Abstract
We present simulation results from a comprehensive molecular dynamics (MD) study of surface-directed spinodal decomposition (SDSD) in unstable symmetric binary mixtures at wetting surfaces. We consider long-ranged and short-ranged surface fields to investigate the early stage wetting kinetics. The attractive part of the long-ranged potential is of the form V(z)∼z^{-n}, where z is the distance from the surface and n is the power-law exponent. We find that the wetting-layer thickness R_{1}(t) at very early times exhibits a power-law growth with an exponent α=1/(n+2). It then crosses over to a universal fast-mode regime with α=3/2. In contrast, for the short-ranged surface potential, a logarithmic behavior in R_{1}(t) is observed at initial times. Remarkably, similar rapid growth is seen in this case too. We provide phenomenological arguments to understand these growth laws. Our MD results firmly establish the existence of universal fast-mode kinetics and settle the related controversy.
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Affiliation(s)
| | - Prabhat K Jaiswal
- Department of Physics, Indian Institute of Technology Jodhpur, Karwar 342030, India
| | - Madhu Priya
- Department of Physics, Birla Institute of Technology Mesra, Ranchi 835215, India
| | - Sanjay Puri
- School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067, India
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Abstract
Dormancy is an evolutionarily conserved protective mechanism widely observed in nature. A pathological example is found during cancer metastasis, where cancer cells disseminate from the primary tumor, home to secondary organs, and enter a growth-arrested state, which could last for decades. Recent studies have pointed toward the microenvironment being heavily involved in inducing, preserving, or ceasing this dormant state, with a strong focus on identifying specific molecular mechanisms and signaling pathways. Increasing evidence now suggests the existence of an interplay between intracellular as well as extracellular biochemical and mechanical cues in guiding such processes. Despite the inherent complexities associated with dormancy, proliferation, and growth of cancer cells and tumor tissues, viewing these phenomena from a physical perspective allows for a more global description, independent from many details of the systems. Building on the analogies between tissues and fluids and thermodynamic phase separation concepts, we classify a number of proposed mechanisms in terms of a thermodynamic metastability of the tumor with respect to growth. This can be governed by interaction with the microenvironment in the form of adherence (wetting) to a substrate or by mechanical confinement of the surrounding extracellular matrix. By drawing parallels with clinical and experimental data, we advance the notion that the local energy minima, or metastable states, emerging in the tissue droplet growth kinetics can be associated with a dormant state. Despite its simplicity, the provided framework captures several aspects associated with cancer dormancy and tumor growth.
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Goyal A, van der Schoot P, Toschi F. Impact of the prequench state of binary fluid mixtures on surface-directed spinodal decomposition. Phys Rev E 2021; 103:042801. [PMID: 34005894 DOI: 10.1103/physreve.103.042801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Accepted: 03/18/2021] [Indexed: 11/07/2022]
Abstract
Using lattice Boltzmann simulations we investigate the impact of the amplitude of concentration fluctuations in binary fluid mixtures prior to demixing when in contact with a surface that is preferentially wet by one of the components. We find a bicontinuous structure near the surface for an initial, prequench state of the mixture close to the critical point where the amplitude of concentration fluctuations is large. In contrast, if the initial state of the mixture is not near the critical point and concentration fluctuations are relatively weak, then the morphology is not bicontinuous but remains layered until the very late stages of coarsening. In both cases, it is the morphology of a depletion layer rich in the nonpreferred component that dictates the growth exponent of the thickness of the fluid layer that is in direct contact with the substrate. In the early stages of demixing, we find a growth exponent consistent with a value of 1/4 for a prequench state away from the critical point, which is different from the usual diffusive scaling exponent of 1/3 that we recover for a prequench state close to the critical point. We attribute this to the structure of a depletion layer that is penetrated by tubes of the preferred fluid, connecting the wetting layer to the bulk fluid even in the early stages if the initial state is characterized by concentration fluctuations that are large in amplitude. Furthermore, we find that in the late stages of demixing the flow through these tubes results in significant in-plane concentration variations near the substrate, leading to dropletlike structures with a concentration lower than the average concentration in the wetting layer. This causes a deceleration in the growth of the wetting layer in the very late stages of the demixing. Irrespective of the prequench state of the mixture, the late stages of the demixing process produce the same growth law for the layer thickness, with a scaling exponent of unity usually associated with the impact of hydrodynamic flow fields.
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Affiliation(s)
- Abheeti Goyal
- Fluids and Flows Group, Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands and Theory of Polymers and Soft Matter Group, Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Paul van der Schoot
- Theory of Polymers and Soft Matter Group, Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Federico Toschi
- Fluids and Flows Group, Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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6
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Das P, Jaiswal PK, Puri S. Surface-directed spinodal decomposition on morphologically patterned substrates. Phys Rev E 2020; 102:032801. [PMID: 33076022 DOI: 10.1103/physreve.102.032801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 08/23/2020] [Indexed: 06/11/2023]
Abstract
This paper is the second in a two-part exposition on surface-directed spinodal decomposition (SDSD), i.e., the interplay of kinetics of wetting and phase separation at a surface which is wetted by one of the components of a binary mixture. In our first paper [P. Das, P. K. Jaiswal, and S. Puri, Phys. Rev. E 102, 012803 (2020)2470-004510.1103/PhysRevE.102.012803], we studied SDSD on chemically heterogeneous and physically flat substrates. In this paper, we study SDSD on a chemically homogeneous but morphologically patterned substrate. Such substrates arise in a vast variety of technological applications. Our goal is to provide a theoretical understanding of SDSD in this context. We present detailed numerical results for domain growth both inside and above the grooves in the substrate. The morphological evolution can be understood in terms of the interference of SDSD waves originating from the different surfaces comprising the substrate.
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Affiliation(s)
- Prasenjit Das
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot 76100, Israel
- School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| | - Prabhat K Jaiswal
- Department of Physics, Indian Institute of Technology Jodhpur, Karwar 342037, India
| | - Sanjay Puri
- School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067, India
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7
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Wise MB, Millett PC. Two-dimensional bicontinuous structures from symmetric surface-directed spinodal decomposition in thin films. Phys Rev E 2018; 98:022601. [PMID: 30253514 DOI: 10.1103/physreve.98.022601] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Indexed: 11/07/2022]
Abstract
We present numerical simulations of symmetric surface-directed spinodal decomposition in thin films with varying film thickness and film composition. The simulations utilize a Cahn-Hilliard model to describe phase separation kinetics in confined film geometries. The systems consist of two phases: a wetting phase that completely wets the top and bottom surfaces, and a nonwetting phase. Three distinct morphologies emerge including a discrete nonwetting morphology, a discrete wetting morphology, as well as a unique two-dimensional bicontinuous morphology that forms for specific values of film thickness and composition. The morphologies are analyzed with a Hoshen-Kopelman algorithm to quantify the degree of continuity of the nonwetting phase, and a morphology map is presented to guide future work.
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Affiliation(s)
- Michael B Wise
- Department of Mechanical Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA
| | - Paul C Millett
- Department of Mechanical Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA
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8
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Das SK. Atomistic simulations of liquid–liquid coexistence in confinement: comparison of thermodynamics and kinetics with bulk. MOLECULAR SIMULATION 2015. [DOI: 10.1080/08927022.2014.998214] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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9
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Jaiswal PK, Puri S, Das SK. Surface-directed spinodal decomposition: a molecular dynamics study. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 85:051137. [PMID: 23004733 DOI: 10.1103/physreve.85.051137] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Indexed: 06/01/2023]
Abstract
We use molecular dynamics simulations to study surface-directed spinodal decomposition in unstable binary AB fluid mixtures at wetting surfaces. The thickness of the wetting layer R1 grows with time t as a power law (R1∼tθ). We find that hydrodynamic effects result in a crossover of the growth exponent from θ≃1/3 to 1. We also present results for the layerwise correlation functions and domain length scales.
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Affiliation(s)
- Prabhat K Jaiswal
- School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110 067, India
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10
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Jamie EAG, Dullens RPA, Aarts DGAL. Surface Effects on the Demixing of Colloid–Polymer Systems. J Phys Chem B 2011; 115:13168-74. [DOI: 10.1021/jp207250q] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- E. A. G. Jamie
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - R. P. A. Dullens
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - D. G. A. L. Aarts
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
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11
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Jaiswal PK, Puri S, Das SK. Kinetics of surface enrichment: A molecular dynamics study. J Chem Phys 2010; 133:154901. [DOI: 10.1063/1.3491833] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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12
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Hore MJA, Laradji M. Dissipative particle dynamics simulation of the interplay between spinodal decomposition and wetting in thin film binary fluids. J Chem Phys 2010; 132:024908. [DOI: 10.1063/1.3281689] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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13
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Das SK, Horbach J, Binder K. Kinetics of phase separation in thin films: lattice versus continuum models for solid binary mixtures. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 79:021602. [PMID: 19391756 DOI: 10.1103/physreve.79.021602] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2008] [Indexed: 05/27/2023]
Abstract
A description of phase separation kinetics for solid binary (A,B) mixtures in thin film geometry based on the Kawasaki spin-exchange kinetic Ising model is presented in a discrete lattice molecular field formulation. It is shown that the model describes the interplay of wetting layer formation and lateral phase separation, which leads to a characteristic domain size l(t) in the directions parallel to the confining walls that grows according to the Lifshitz-Slyozov t;{13} law with time t after the quench. Near the critical point of the model, the description is shown to be equivalent to the standard treatments based on Ginzburg-Landau models. Unlike the latter, the present treatment is reliable also at temperatures far below criticality, where the correlation length in the bulk is only of the order of a lattice spacing, and steep concentration variations may occur near the walls, invalidating the gradient square approximation. A further merit is that the relation to the interaction parameters in the bulk and at the walls is always transparent, and the correct free energy at low temperatures is consistent with the time evolution by construction.
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Affiliation(s)
- Subir K Das
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India
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14
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ten Bosch A. Transport theory at the nanoscale. II. Interface dynamics for film growth. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2006; 73:031606. [PMID: 16605536 DOI: 10.1103/physreve.73.031606] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2005] [Revised: 10/20/2005] [Indexed: 05/08/2023]
Abstract
Conditions for surface nucleation and growth of a film are determined in a diffuse interface model. A method is given, derived from a Fokker-Planck equation for the nonequilibrium particle distribution, which links atomic and mesoscopic events in a rheological description similar to the classical continuum theory of fluid flow. Film nucleation and growth are modeled by the spatially inhomogeneous continuous evolution of the instantaneous density profile which measures the average number of particles or molecules at given time and position. It is shown how an alteration in the distribution of particles in the vicinity of the boundary between parent and product phases induces transient film growth and damped vibrations at the surface. The method is general but as an illustration, the condensation of a simple classical fluid on cooling is considered in detail.
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Affiliation(s)
- A ten Bosch
- Laboratoire de Physique de la Matière Condensèe, CNRS 6622, Parc Valrose, F-06108 Nice Cedex 2, France.
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15
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Das SK, Puri S, Horbach J, Binder K. Molecular dynamics study of phase separation kinetics in thin films. PHYSICAL REVIEW LETTERS 2006; 96:016107. [PMID: 16486484 DOI: 10.1103/physrevlett.96.016107] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2005] [Indexed: 05/06/2023]
Abstract
We use molecular dynamics to simulate experiments where a symmetric binary fluid mixture (AB), confined between walls that preferentially attract one component (A), is quenched from the one-phase region into the miscibility gap. Surface enrichment occurs during the early stages, yielding a B-rich mixture in the film center with well-defined A-rich droplets. The droplet size grows with time as l(t) proportional t(2/3) after a transient regime. The present atomistic model is also compared to mesoscopic coarse-grained models for this problem.
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Affiliation(s)
- Subir K Das
- Institut für Physik, Johannes Gutenberg-Universität, D-55099 Mainz, Staudinger Weg 7, Germany
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16
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Das SK, Puri S, Horbach J, Binder K. Kinetics of phase separation in thin films: simulations for the diffusive case. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 72:061603. [PMID: 16485955 DOI: 10.1103/physreve.72.061603] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2005] [Indexed: 05/06/2023]
Abstract
We study the diffusion-driven kinetics of phase separation of a symmetric binary mixture (AB), confined in a thin-film geometry between two parallel walls. We consider cases where (i) both walls preferentially attract the same component (A), and (ii) one wall attracts and the other wall attracts (with the same strength). We focus on the interplay of phase separation and wetting at the walls, which is referred to as surface-directed spinodal decomposition (SDSD). The formation of SDSD waves at the two surfaces, with wave vectors oriented perpendicular to them, often results in a metastable layered state (also referred to as "stratified morphology"). This state is reminiscent of the situation where the thin film is still in the one-phase region but the surfaces are completely wet, and hence coated with thick wetting layers. This metastable state decays by spinodal fluctuations and crosses over to an asymptotic growth regime characterized by the lateral coarsening of pancakelike domains. These pancakes may or may not be coated by precursors of wetting layers. We use Langevin simulations to study this crossover and the growth kinetics in the asymptotic coarsening regime.
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Affiliation(s)
- Subir K Das
- Institut für Physik, Johannes Gutenberg-Universität, D-55099 Mainz, Staudinger Weg 7, Germany
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17
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Wang H, Douglas JF, Satija SK, Composto RJ, Han CC. Early-stage compositional segregation in polymer-blend films. ACTA ACUST UNITED AC 2005; 67:061801. [PMID: 16241248 DOI: 10.1103/physreve.67.061801] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2003] [Indexed: 11/07/2022]
Abstract
The existence of a transient period during the surface enrichment of a binary polymer blend by one of its components has been suggested by previous theoretical and experimental studies as well as computer simulations. Taking advantage of the high depth resolution of neutron reflectivity and the slow dynamics of polymers near their glass transition, we investigate this early-stage surface compositional enrichment in a phase separating polymer blend for the first time. Two stages of surface enrichment layer growth are observed. A rapid local surface enrichment at the chain segmental level occurs first, followed by a slower growth of a diffuse layer having a scale on the order of the bulk correlation length and the radius of gyration of the surface enriching polymer chains.
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Affiliation(s)
- H Wang
- Department of Materials Science and Engineering, Michigan Technological University, Michigan 49931, USA.
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19
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Bastea S, Esposito R, Lebowitz JL, Marra R. Hydrodynamics of binary fluid phase segregation. PHYSICAL REVIEW LETTERS 2002; 89:235701. [PMID: 12485020 DOI: 10.1103/physrevlett.89.235701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2002] [Indexed: 05/24/2023]
Abstract
Starting with the Vlasov-Boltzmann equation for a binary fluid mixture, we derive an equation for the velocity field u when the system is segregated into two phases (at low temperatures) with a sharp interface between them. u satisfies the incompressible Navier-Stokes equations together with a jump boundary condition for the pressure across the interface which, in turn, moves with a velocity given by the normal component of u. Numerical simulations of the Vlasov-Boltzmann equations for shear flows parallel and perpendicular to the interface in a phase segregated mixture support this analysis. We expect similar behavior in real fluid mixtures.
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Affiliation(s)
- Sorin Bastea
- Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550, USA
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Puri S, Binder K. Surface-directed phase separation with off-critical composition: analytical and numerical results. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2002; 66:061602. [PMID: 12513292 DOI: 10.1103/physreve.66.061602] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2002] [Indexed: 05/24/2023]
Abstract
We study the interplay of wetting and phase separation in an unstable binary mixture (AB) with off-critical composition, placed in contact with a surface which prefers the component A. We consider surface potentials V(z) approximately z(-n), where z is the distance from the surface, and present analytical arguments and detailed numerical results to elucidate wetting-layer kinetics for arbitrary mixture compositions. If the preferred component is the minority phase, the wetting-layer thickness exhibits a potential-specific behavior at early times tau, R1 approximately tau(1/(n+2)), before crossing over to the universal growth law, R1 approximately tau(1/3). On the other hand, if the preferred component is the majority phase, there is a crossover from potential-specific growth (as before) to a slower growth regime.
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Affiliation(s)
- Sanjay Puri
- School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067, India
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21
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Moffitt M, Rharbi Y, Li H, Winnik MA. Novel Morphology Evolution in Thick Films of a Polymer Blend. Macromolecules 2002. [DOI: 10.1021/ma011679+] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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22
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Kuksenok O, Yeomans JM, Balazs AC. Using patterned substrates to promote mixing in microchannels. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2002; 65:031502. [PMID: 11909061 DOI: 10.1103/physreve.65.031502] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2001] [Indexed: 05/23/2023]
Abstract
Using a lattice Boltzmann model for fluid dynamics, we investigate the flow and phase behavior of a binary fluid moving over a patterned substrate within a microchannel. The binary fluid consists of two immiscible components, A and B, and this liquid is subjected to a Poiseuille flow. The substrate is decorated with a checkerboard pattern of A- and B-like patches. Through a coupling of hydrodynamics and thermodynamics, each component is driven to flow from the nonwettable domains to wettable regions. As a consequence, the A and B fluids undergo extensive mixing within the microchannels. We investigate how the degree of mixing depends on the size of the patches, the velocity of the imposed flow field, and the characteristics of the fluid. The results provide guidelines for creating localized "mixing stations" within microfluidic devices. The findings also reveal how a combination of imposed flow fields and surface patterning can be exploited to control the phase behavior of complex fluids.
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Affiliation(s)
- Olga Kuksenok
- Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pennsylvania 15261, USA
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