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Rahman MR, Shen L, Ewen JP, Collard B, Heyes DM, Dini D, Smith ER. Non-equilibrium molecular simulations of thin film rupture. J Chem Phys 2023; 158:2882242. [PMID: 37093990 DOI: 10.1063/5.0149974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Accepted: 03/30/2023] [Indexed: 04/26/2023] Open
Abstract
The retraction of thin films, as described by the Taylor-Culick (TC) theory, is subject to widespread debate, particularly for films at the nanoscale. We use non-equilibrium molecular dynamics simulations to explore the validity of the assumptions used in continuum models by tracking the evolution of holes in a film. By deriving a new mathematical form for the surface shape and considering a locally varying surface tension at the front of the retracting film, we reconcile the original theory with our simulation to recover a corrected TC speed valid at the nanoscale.
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Affiliation(s)
- Muhammad Rizwanur Rahman
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Li Shen
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - James P Ewen
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Benjamin Collard
- Department of Materials Science, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - D M Heyes
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Daniele Dini
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - E R Smith
- Department of Mechanical and Aerospace Engineering, Brunel University London, Uxbridge UB8 3PH, United Kingdom
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2
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Sládek J, Hlinomaz K, Mirza I, Levy Y, Derrien TJY, Cimrman M, Nagisetty SS, Čermák J, Stuchlíková TH, Stuchlík J, Bulgakova NM. Highly Regular LIPSS on Thin Molybdenum Films: Optimization and Generic Criteria. MATERIALS (BASEL, SWITZERLAND) 2023; 16:2883. [PMID: 37049179 PMCID: PMC10095765 DOI: 10.3390/ma16072883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 03/24/2023] [Accepted: 03/31/2023] [Indexed: 06/19/2023]
Abstract
A systematic experimental study was performed to determine laser irradiation conditions for the large-area fabrication of highly regular laser-induced periodic surface structures (HR-LIPSS) on a 220 nm thick Mo film deposited on fused silica. The LIPSS were fabricated by scanning a linearly polarized, spatially Gaussian laser beam at 1030 nm wavelength and 1.4 ps pulse duration over the sample surface at 1 kHz repetition rate. Scanning electron microscope images of the produced structures were analyzed using the criterion of the dispersion of the LIPSS orientation angle (DLOA). Favorable conditions, in terms of laser fluence and beam scanning overlaps, were identified for achieving DLOA values <10∘. To gain insight into the material behavior under these irradiation conditions, a theoretical analysis of the film heating was performed, and surface plasmon polariton excitation is discussed. A possible effect of the film dewetting from the dielectric substrate is deliberated.
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Affiliation(s)
- Juraj Sládek
- HiLASE Centre, Institute of Physics of the Czech Academy of Sciences, Za Radnicí 828, 252 41 Dolní Břežany, Czech Republic
- Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Trojanova 13, 120 00 Prague, Czech Republic
| | - Kryštof Hlinomaz
- HiLASE Centre, Institute of Physics of the Czech Academy of Sciences, Za Radnicí 828, 252 41 Dolní Břežany, Czech Republic
- Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Trojanova 13, 120 00 Prague, Czech Republic
| | - Inam Mirza
- HiLASE Centre, Institute of Physics of the Czech Academy of Sciences, Za Radnicí 828, 252 41 Dolní Břežany, Czech Republic
| | - Yoann Levy
- HiLASE Centre, Institute of Physics of the Czech Academy of Sciences, Za Radnicí 828, 252 41 Dolní Břežany, Czech Republic
| | - Thibault J.-Y. Derrien
- HiLASE Centre, Institute of Physics of the Czech Academy of Sciences, Za Radnicí 828, 252 41 Dolní Břežany, Czech Republic
| | - Martin Cimrman
- HiLASE Centre, Institute of Physics of the Czech Academy of Sciences, Za Radnicí 828, 252 41 Dolní Břežany, Czech Republic
- Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Trojanova 13, 120 00 Prague, Czech Republic
| | - Siva S. Nagisetty
- Coherent Laser Systems GmbH & Co. KG, Hans Boeckler Str. 12, 37079 Göttingen, Germany
| | - Jan Čermák
- Institute of Physics of the Czech Academy of Sciences, Cukrovarnická 10, 162 00 Prague, Czech Republic
| | - The Ha Stuchlíková
- Institute of Physics of the Czech Academy of Sciences, Cukrovarnická 10, 162 00 Prague, Czech Republic
| | - Jiří Stuchlík
- Institute of Physics of the Czech Academy of Sciences, Cukrovarnická 10, 162 00 Prague, Czech Republic
| | - Nadezhda M. Bulgakova
- HiLASE Centre, Institute of Physics of the Czech Academy of Sciences, Za Radnicí 828, 252 41 Dolní Břežany, Czech Republic
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3
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Vanegas JM, Peterson D, Lakoba TI, Kotov VN. Spinodal de-wetting of light liquids on graphene. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:175001. [PMID: 35086067 DOI: 10.1088/1361-648x/ac4f7e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Accepted: 01/27/2022] [Indexed: 06/14/2023]
Abstract
We demonstrate theoretically the possibility of spinodal de-wetting in heterostructures made of light-atom liquids (hydrogen, helium, and nitrogen) deposited on suspended graphene. Extending our theory of film growth on two-dimensional (2D) materials to include analysis of surface instabilities via the hydrodynamic Cahn-Hilliard-type equation, we characterize in detail the spatial and temporal scales of the resulting spinodal de-wetting patterns. Both linear stability analysis and direct numerical simulations of the surface hydrodynamics show micron-sized (generally material dependent) patterns of 'dry' regions. The physical reason for the development of such instabilities on graphene can be traced back to the inherently weak van der Waals interactions between atomically thin materials and atoms in the liquid. Thus 2D materials could represent a new theoretical and technological platform for studies of spinodal de-wetting.
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Affiliation(s)
- Juan M Vanegas
- Department of Physics, University of Vermont, Burlington, VT 05405, United States of America
| | - David Peterson
- Department of Physics, University of Vermont, Burlington, VT 05405, United States of America
| | - Taras I Lakoba
- Department of Mathematics and Statistics, University of Vermont, Burlington, VT 05405, United States of America
| | - Valeri N Kotov
- Department of Physics, University of Vermont, Burlington, VT 05405, United States of America
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4
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Henkel C, Snoeijer JH, Thiele U. Gradient-dynamics model for liquid drops on elastic substrates. SOFT MATTER 2021; 17:10359-10375. [PMID: 34747426 DOI: 10.1039/d1sm01032h] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The wetting of soft elastic substrates exhibits many features that have no counterpart on rigid surfaces. Modelling the detailed elastocapillary interactions is challenging, and has so far been limited to single contact lines or single drops. Here we propose a reduced long-wave model that captures the main qualitative features of statics and dynamics of soft wetting, but which can be applied to ensembles of droplets. The model has the form of a gradient dynamics on an underlying free energy that reflects capillarity, wettability and compressional elasticity. With the model we first recover the double transition in the equilibrium contact angles that occurs when increasing substrate softness from ideally rigid towards very soft (i.e., liquid). Second, the spreading of single drops of partially and completely wetting liquids is considered showing that known dependencies of the dynamic contact angle on contact line velocity are well reproduced. Finally, we go beyond the single droplet picture and consider the coarsening for a two-drop system as well as for a large ensemble of drops. It is shown that the dominant coarsening mode changes with substrate softness in a nontrivial way.
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Affiliation(s)
- Christopher Henkel
- Institut für Theoretische Physik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 9, 48149 Münster, Germany.
| | - Jacco H Snoeijer
- Physics of Fluids Group and J. M. Burgers Centre for Fluid Dynamics, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Uwe Thiele
- Institut für Theoretische Physik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 9, 48149 Münster, Germany.
- Center for Nonlinear Science (CeNoS), Westfälische Wilhelms-Universität Münster, Corrensstr. 2, 48149 Münster, Germany
- Center for Multiscale Theory and Computation (CMTC), Westfälische Wilhelms-Universität, Corrensstr. 40, 48149 Münster, Germany
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Das A, Mukherjee R. Feature Size Modulation in Dewetting of Nanoparticle-Containing Ultrathin Polymer Films. Macromolecules 2021. [DOI: 10.1021/acs.macromol.1c00012] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Anuja Das
- Instability and Soft Patterning Laboratory, Department of Chemical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, West Bengal, India
| | - Rabibrata Mukherjee
- Instability and Soft Patterning Laboratory, Department of Chemical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, West Bengal, India
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Kumar S, Ghosh A, Chaudhuri J, Timung S, Dasmahapatra AK, Bandyopadhyay D. Self-organized spreading of droplets to fluid toroids. J Colloid Interface Sci 2020; 578:738-748. [DOI: 10.1016/j.jcis.2020.06.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 06/03/2020] [Accepted: 06/03/2020] [Indexed: 10/24/2022]
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8
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Wu Y, Wang F, Ma S, Selzer M, Nestler B. How do chemical patterns affect equilibrium droplet shapes? SOFT MATTER 2020; 16:6115-6127. [PMID: 32638820 DOI: 10.1039/d0sm00196a] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
By utilizing a proposed analytical model in combination with the phase-field method, we present a comprehensive study on the effect of chemical patterns on equilibrium droplet morphologies. Here, three influencing factors, the droplet sizes, contact angles, and the ratios of the hydrophilic area to the hydrophobic area, are contemplated. In the analytical model, chemical heterogeneities are described by different non-linear functions. By tuning these functions and the related parameters, the analytical model is capable of calculating the energy landscapes of the system. The chemically patterned surfaces display complex energy landscapes with chemical-heterogeneity-induced local minima, which correspond to the equilibrium morphologies of the droplets. Phase-field (PF) simulations are accordingly conducted and compared with the predicted equilibrium morphologies. In addition, we propose a modified Cassie-Baxter (CB) model to delineate the equilibrium droplet shapes. In contrast to the classic CB model, our extension is not only restricted to the shape with a spherical cap. Both the energy landscape method and the modified CB model are demonstrated to have a good agreement with the PF simulations.
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Affiliation(s)
- Yanchen Wu
- Institute of Applied Materials-Computational Materials Science, Karlsruhe Institute of Technology, Straße am Forum 7, 76131 Karlsruhe, Germany.
| | - Fei Wang
- Institute of Applied Materials-Computational Materials Science, Karlsruhe Institute of Technology, Straße am Forum 7, 76131 Karlsruhe, Germany.
| | - Shaoping Ma
- Institute of Applied Materials-Computational Materials Science, Karlsruhe Institute of Technology, Straße am Forum 7, 76131 Karlsruhe, Germany.
| | - Michael Selzer
- Institute of Applied Materials-Computational Materials Science, Karlsruhe Institute of Technology, Straße am Forum 7, 76131 Karlsruhe, Germany. and Institute of Digital Materials Science, Karlsruhe University of Applied Sciences, Moltkestraße 30, 76133 Karlsruhe, Germany
| | - Britta Nestler
- Institute of Applied Materials-Computational Materials Science, Karlsruhe Institute of Technology, Straße am Forum 7, 76131 Karlsruhe, Germany. and Institute of Digital Materials Science, Karlsruhe University of Applied Sciences, Moltkestraße 30, 76133 Karlsruhe, Germany
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Lee JS, Kang SJ, Shin JH, Shin YJ, Lee B, Koo JM, Kim TI. Nanoscale-Dewetting-Based Direct Interconnection of Microelectronics for a Deterministic Assembly of Transfer Printing. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e1908422. [PMID: 32297400 DOI: 10.1002/adma.201908422] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 03/04/2020] [Accepted: 03/23/2020] [Indexed: 06/11/2023]
Abstract
As electronics dramatically advance, their components should be fabricated for miniaturized scale, and integrated on limited-size substrates with extremely high density. Current technologies for the integration and interconnection of electronics show some critical limitations in the application of microscale electronics. To address these problems, herein, a new direct and vertical interconnection driven by selective dewetting of a polymer adhesive is introduced. The interconnection system consists of the polymer adhesive and nanosized metal particles, or structured electrodes. Nanoscale-dewetting windows formed by controlling the stability and wetting property of the adhesive polymer are controlled by the interfacial property of the coated polymer adhesive. The adhesive is coated on substrate by a simple spin-coating process, and its ultraviolet curable property allows only the device-mounted parts to be selectively conductive and sticky, while the other parts form insulation and protection layers. The interconnection of the electronics and substrate by adhesive makes it possible to apply the technique to various microsize electronics with electrode size and pitch of 20 µm or less, and endure dramatic temperature change and a long-term high humidity environment. Moreover, over display comprising over 10 000 microscale light-emitting diodes (micro-LEDs), and commercialized microchips are demonstrated with monolithic integration on flexible and transparent substrate.
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Affiliation(s)
- Ju Seung Lee
- School of Chemical Engineering, Sungkyunkwan University (SKKU), Suwon, 16419, Republic of Korea
| | - Seung Ji Kang
- School of Chemical Engineering, Sungkyunkwan University (SKKU), Suwon, 16419, Republic of Korea
| | - Joo Hwan Shin
- School of Chemical Engineering, Sungkyunkwan University (SKKU), Suwon, 16419, Republic of Korea
| | - Yiel Jae Shin
- School of Chemical Engineering, Sungkyunkwan University (SKKU), Suwon, 16419, Republic of Korea
| | - Byunghoon Lee
- Global Technology Center, Samsung Electronics Co., Ltd., 129, Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do, 16677, Republic of Korea
| | - Ja-Myeong Koo
- Global Technology Center, Samsung Electronics Co., Ltd., 129, Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do, 16677, Republic of Korea
| | - Tae-Il Kim
- School of Chemical Engineering, Department of Biomedical Engineering and Biomedical Institute for Convergence at SKKU (BICS), Sungkyunkwan University (SKKU), Suwon, 16419, Republic of Korea
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Ruffino F, Grimaldi MG. Nanostructuration of Thin Metal Films by Pulsed Laser Irradiations: A Review. NANOMATERIALS 2019; 9:nano9081133. [PMID: 31390842 PMCID: PMC6723593 DOI: 10.3390/nano9081133] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 07/30/2019] [Accepted: 07/31/2019] [Indexed: 11/16/2022]
Abstract
Metal nanostructures are, nowadays, extensively used in applications such as catalysis, electronics, sensing, optoelectronics and others. These applications require the possibility to design and fabricate metal nanostructures directly on functional substrates, with specifically controlled shapes, sizes, structures and reduced costs. A promising route towards the controlled fabrication of surface-supported metal nanostructures is the processing of substrate-deposited thin metal films by fast and ultrafast pulsed lasers. In fact, the processes occurring for laser-irradiated metal films (melting, ablation, deformation) can be exploited and controlled on the nanoscale to produce metal nanostructures with the desired shape, size, and surface order. The present paper aims to overview the results concerning the use of fast and ultrafast laser-based fabrication methodologies to obtain metal nanostructures on surfaces from the processing of deposited metal films. The paper aims to focus on the correlation between the process parameter, physical parameters and the morphological/structural properties of the obtained nanostructures. We begin with a review of the basic concepts on the laser-metal films interaction to clarify the main laser, metal film, and substrate parameters governing the metal film evolution under the laser irradiation. The review then aims to provide a comprehensive schematization of some notable classes of metal nanostructures which can be fabricated and establishes general frameworks connecting the processes parameters to the characteristics of the nanostructures. To simplify the discussion, the laser types under considerations are classified into three classes on the basis of the range of the pulse duration: nanosecond-, picosecond-, femtosecond-pulsed lasers. These lasers induce different structuring mechanisms for an irradiated metal film. By discussing these mechanisms, the basic formation processes of micro- and nano-structures is illustrated and justified. A short discussion on the notable applications for the produced metal nanostructures is carried out so as to outline the strengths of the laser-based fabrication processes. Finally, the review shows the innovative contributions that can be proposed in this research field by illustrating the challenges and perspectives.
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Affiliation(s)
- Francesco Ruffino
- Dipartimento di Fisica e Astronomia "Ettore Majorana"-Università di Catania and MATIS CNR-IMM, via S. Sofia 64, 95123 Catania, Italy.
| | - Maria Grazia Grimaldi
- Dipartimento di Fisica e Astronomia "Ettore Majorana"-Università di Catania and MATIS CNR-IMM, via S. Sofia 64, 95123 Catania, Italy
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11
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Continuation for Thin Film Hydrodynamics and Related Scalar Problems. COMPUTATIONAL METHODS IN APPLIED SCIENCES 2019. [DOI: 10.1007/978-3-319-91494-7_13] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
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12
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Rupture of ultrathin solution films on planar solid substrates induced by solute crystallization. J Colloid Interface Sci 2018; 528:63-69. [PMID: 29843063 DOI: 10.1016/j.jcis.2018.05.034] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Revised: 05/10/2018] [Accepted: 05/14/2018] [Indexed: 11/21/2022]
Abstract
On-line optical imaging of continuously thinning planar films in a spin cast configuration reveals the rupture behavior of ultra-thin films of binary mixtures of a volatile solvent and a nonvolatile solute. The pure solvents completely wet the silica substrates whereas the solution films rupture at certain film thicknesses, hrupture, which depend on, c0, the initial weighing in solute concentrations. With small c0, hrupture increases proportional to c0. With high c0, all films rupture at hrupture≈50nm, independent of c0. The findings can be explained by the solute enrichment during the evaporative thinning. Solute crystallization at the liquid/substrate interface upon reaching solute supersaturation leads to locally different wetting properties. This induces locally the rupture of the film as soon as it is sufficiently thin. A proper data rescaling based on this scenario yields a universal rupture behavior of various different solvent/solute mixtures.
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Abo Jabal M, Egbaria A, Zigelman A, Thiele U, Manor O. Connecting Monotonic and Oscillatory Motions of the Meniscus of a Volatile Polymer Solution to the Transport of Polymer Coils and Deposit Morphology. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:11784-11794. [PMID: 30179481 DOI: 10.1021/acs.langmuir.8b02268] [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
We study the deposition mechanisms of polymer from a confined meniscus of volatile liquid. In particular, we investigate the physical processes that are responsible for qualitative changes in the pattern deposition of polymer and the underlying interplay of the state of pattern deposition, motion of the meniscus, and the transport of polymer within the meniscus. As a model system we evaporate a solution of poly(methyl methacrylate) (PMMA) in toluene. Different deposition patterns are observed when varying the molecular mass, the initial concentration of the solute, and temperature; these are systematically presented in the form of morphological phase diagrams. The modi of deposition and meniscus motion are correlated. They vary with the ratio between the evaporation-driven convective flux and the diffusive flux of the polymer coils in the solution. In the case of a diffusion-dominated solute transport, the solution monotonically dewets the solid substrate by evaporation, supporting continuous contact line motion and continuous polymer deposition. However, a convection-dominated transport results in an oscillatory ratcheting dewetting-wetting motion of the contact line with more pronounced dewetting phases. The deposition process is then periodic and produces a stripe pattern. The oscillatory motion of the meniscus differs from the well documented stick-slip motion of the meniscus, observed as well, and is attributed to the opposing influences of evaporation and Marangoni stresses, which alternately dominate the deposition process.
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Affiliation(s)
- Mohammad Abo Jabal
- Wolfson Department of Chemical Engineering , Technion - Israel Institute of Technology , Haifa , Israel 32000
| | - Ala Egbaria
- Wolfson Department of Chemical Engineering , Technion - Israel Institute of Technology , Haifa , Israel 32000
| | - Anna Zigelman
- Wolfson Department of Chemical Engineering , Technion - Israel Institute of Technology , Haifa , Israel 32000
| | - Uwe Thiele
- Institut für Theoretische Physik , Westfälische Wilhelms-Universität Münster , Wilhelm Klemm Str. 9 , 48149 Münster , Germany
- Center of Nonlinear Science (CeNoS) , Westfälische Wilhelms Universität Münster , Corrensstr. 2 , 48149 Münster , Germany
| | - Ofer Manor
- Wolfson Department of Chemical Engineering , Technion - Israel Institute of Technology , Haifa , Israel 32000
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14
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Thiele U. Recent advances in and future challenges for mesoscopic hydrodynamic modelling of complex wetting. Colloids Surf A Physicochem Eng Asp 2018. [DOI: 10.1016/j.colsurfa.2018.05.049] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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15
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Kim T, Kim W. Viscous dewetting of metastable liquid films on substrates with microgrooves. J Colloid Interface Sci 2018. [DOI: 10.1016/j.jcis.2018.02.073] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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16
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Xu L, Bandyopadhyay D, Reddy PDS, Sharma A, Joo SW. Giant Slip Induced Anomalous Dewetting of an Ultrathin Film on a Viscous Sublayer. Sci Rep 2017; 7:14776. [PMID: 29116103 PMCID: PMC5676695 DOI: 10.1038/s41598-017-14861-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 09/25/2017] [Indexed: 11/23/2022] Open
Abstract
A 'giant' slip dynamics was engineered to a highly confined interface of a dewetting polymethylmethacrylate (PMMA) ultrathin film by introducing a lubricating viscous polystyrene (PS) sublayer. The crossover of regimes from no-slip to giant-slip was engendered by tuning the viscosity and thickness of the sublayer. A long-range hole-rim interaction with increase in slippage on the PMMA-PS interface transformed the circular holes on the PMMA surface into the noncircular faceted ones. The extent of the slippage and the transition of the length scales from slip-dominated to no-slip regime were evaluated using a general linear stability analysis. The proposed formulation provided an analytical tool to evaluate the slippage effective at the soft and deformable liquid-liquid interfaces.
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Affiliation(s)
- Lin Xu
- Laboratory of Surface Physics and Chemistry, Guizhou Education University, Guiyang, 550018, P. R. China
| | - Dipankar Bandyopadhyay
- Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati, 781039, India.
| | | | - Ashutosh Sharma
- Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur, 208016, India.
| | - Sang Woo Joo
- School of Mechanical Engineering, Yeungnam University, Gyongsan, 712-749, South Korea.
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18
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Retamal MJ, Corrales TP, Cisternas MA, Moraga NH, Diaz DI, Catalan RE, Seifert B, Huber P, Volkmann UG. Surface Morphology of Vapor-Deposited Chitosan: Evidence of Solid-State Dewetting during the Formation of Biopolymer Films. Biomacromolecules 2016; 17:1142-9. [PMID: 26811988 DOI: 10.1021/acs.biomac.5b01750] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Chitosan is a useful and versatile biopolymer with several industrial and biological applications. Whereas its physical and physicochemical bulk properties have been explored quite intensively in the past, there is a lack of studies regarding the morphology and growth mechanisms of thin films of this biopolymer. Of particular interest for applications in bionanotechnology are ultrathin films with thicknesses under 500 Å. Here, we present a study of thin chitosan films prepared in a dry process using physical vapor deposition and in situ ellipsometric monitoring. The prepared films were analyzed with atomic force microscopy in order to correlate surface morphology with evaporation parameters. We find that the surface morphology of our final thin films depends on both the optical thickness, i.e., measured with ellipsometry, and the deposition rate. Our work shows that ultrathin biopolymer films can undergo dewetting during film formation, even in the absence of solvents and thermal annealing.
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Affiliation(s)
| | - Tomas P Corrales
- Instituto de Alta Investigacion, Universidad de Tarapaca , Casilla 7-D, 1000007 Arica, Chile
| | | | | | | | | | | | - Patrick Huber
- Institute of Materials Physics and Technology, Hamburg University of Technology (TUHH) , D-21073 Hamburg-Harburg, Germany
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19
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Hens A, Mondal K, Biswas G, Bandyopadhyay D. Pathways from disordered to ordered nanostructures from defect guided dewetting of ultrathin bilayers. J Colloid Interface Sci 2016; 465:128-39. [DOI: 10.1016/j.jcis.2015.11.046] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Revised: 11/18/2015] [Accepted: 11/20/2015] [Indexed: 12/15/2022]
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Mukherjee R, Sharma A. Instability, self-organization and pattern formation in thin soft films. SOFT MATTER 2015; 11:8717-8740. [PMID: 26412507 DOI: 10.1039/c5sm01724f] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The free surface of a thin soft polymer film is often found to become unstable and self-organizes into various meso-scale structures. In this article we classify the instability of a thin polymer film into three broad categories, which are: category 1: instability of an ultra-thin (<100 nm) viscous film engendered by amplification of thermally excited surface capillary waves due to interfacial dispersive van der Waals forces; category 2: instability arising from the attractive inter-surface interactions between the free surface of a soft film exhibiting room temperature elasticity and another rigid surface in its contact proximity; and category 3: instability caused by an externally applied field such as an electric field or a thermal gradient, observed in both viscous and elastic films. We review the salient features of each instability class and highlight how characteristic length scales, feature morphologies, evolution pathways, etc. depend on initial properties such as film thickness, visco-elasticity (rheology), residual stress, and film preparation conditions. We emphasize various possible strategies for aligning and ordering of the otherwise isotropic structures by combining the essential concepts of bottom-up and top-down approaches. A perspective, including a possible future direction of research, novelty and limitations of the methods, particularly in comparison to the existing patterning techniques, is also presented for each setting.
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Affiliation(s)
- Rabibrata Mukherjee
- Instability and Soft Patterning Laboratory, Department of Chemical Engineering, Indian Institute of Technology, Kharagpur, 721 302, India.
| | - Ashutosh Sharma
- Department of Chemical Engineering and Nano-science Center, Indian Institute of Technology, Kanpur, 208016, India.
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21
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Alizadeh Pahlavan A, Cueto-Felgueroso L, McKinley GH, Juanes R. Thin Films in Partial Wetting: Internal Selection of Contact-Line Dynamics. PHYSICAL REVIEW LETTERS 2015; 115:034502. [PMID: 26230798 DOI: 10.1103/physrevlett.115.034502] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Indexed: 06/04/2023]
Abstract
When a liquid touches a solid surface, it spreads to minimize the system's energy. The classic thin-film model describes the spreading as an interplay between gravity, capillarity, and viscous forces, but it cannot see an end to this process as it does not account for the nonhydrodynamic liquid-solid interactions. While these interactions are important only close to the contact line, where the liquid, solid, and gas meet, they have macroscopic implications: in the partial-wetting regime, a liquid puddle ultimately stops spreading. We show that by incorporating these intermolecular interactions, the free energy of the system at equilibrium can be cast in a Cahn-Hilliard framework with a height-dependent interfacial tension. Using this free energy, we derive a mesoscopic thin-film model that describes the statics and dynamics of liquid spreading in the partial-wetting regime. The height dependence of the interfacial tension introduces a localized apparent slip in the contact-line region and leads to compactly supported spreading states. In our model, the contact-line dynamics emerge naturally as part of the solution and are therefore nonlocally coupled to the bulk flow. Surprisingly, we find that even in the gravity-dominated regime, the dynamic contact angle follows the Cox-Voinov law.
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Affiliation(s)
- Amir Alizadeh Pahlavan
- Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - Luis Cueto-Felgueroso
- Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
- Technical University of Madrid, Ciudad Universitaria, 28040 Madrid, Spain
| | - Gareth H McKinley
- Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
| | - Ruben Juanes
- Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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22
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Verma A, Sekhar S, Sachan P, Reddy PDS, Sharma A. Control of Morphologies and Length Scales in Intensified Dewetting of Electron Beam Modified Polymer Thin Films under a Liquid Solvent Mixture. Macromolecules 2015. [DOI: 10.1021/acs.macromol.5b00029] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ankur Verma
- Department of Chemical Engineering
and DST Unit on Nanosciences, Indian Institute of Technology Kanpur, Kanpur (UP), 208016 India
| | - Satya Sekhar
- Department of Chemical Engineering
and DST Unit on Nanosciences, Indian Institute of Technology Kanpur, Kanpur (UP), 208016 India
| | - Priyanka Sachan
- Department of Chemical Engineering
and DST Unit on Nanosciences, Indian Institute of Technology Kanpur, Kanpur (UP), 208016 India
| | - P. Dinesh Sankar Reddy
- Department of Chemical Engineering
and DST Unit on Nanosciences, Indian Institute of Technology Kanpur, Kanpur (UP), 208016 India
| | - Ashutosh Sharma
- Department of Chemical Engineering
and DST Unit on Nanosciences, Indian Institute of Technology Kanpur, Kanpur (UP), 208016 India
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23
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Ravi B, Mukherjee R, Bandyopadhyay D. Solvent vapour mediated spontaneous healing of self-organized defects of liquid crystal films. SOFT MATTER 2015; 11:139-146. [PMID: 25372336 DOI: 10.1039/c4sm02111h] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Ultrathin liquid crystal films showed a nematic to isotropic transition when exposed to solvent vapour for a short duration while a reverse isotropic to nematic transition was observed when the film was isolated from the solvent exposure. The phase transitions were associated with the appearance and fading of surface patterns as the solvent molecules diffused into and out of the film matrix, resulting in the destruction or restoration of the orientational order. A long-time solvent vapour exposure caused the dewetting of the film on the surface, which was demonstrated by the formation of holes and their growth in size with the progress of time. Even at this stage, withdrawal of the solvent exposure produced an array of nematic fingers, which nearly self-healed the dewetted holes. The change in contact angle due to the phase transition coupled with the imbalance of osmotic pressure across the contact line due to the differential rate of solvent evaporation from the film and the hole helped the fingers to grow towards the centre of the hole. The appearance of the fingers upon withdrawal of the solvent exposure and their disappearance upon exposure to solvent were also found to be a nearly reversible process. These findings could significantly contribute to the development of vapour sensors and self-healing surfaces using liquid crystal thin films.
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Affiliation(s)
- Bolleddu Ravi
- Department of Chemical Engineering, Indian Institute of Technology Guwahati, India.
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24
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Datt C, Thampi SP, Govindarajan R. Morphological evolution of domains in spinodal decomposition. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 91:010101. [PMID: 25679549 DOI: 10.1103/physreve.91.010101] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Indexed: 06/04/2023]
Abstract
Domain growth in spinodal decomposition is usually described by a single time-evolving length scale. We show that the evolution of morphology of domains is nonmonotonic. The domains elongate rapidly at first and then, with the help of hydrodynamics, return to a more circular shape. The initial elongation phase does not alter with hydrodynamics. A small deviation from critical composition changes the morphology dramatically.
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Affiliation(s)
- Charu Datt
- Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research, 21 Brundavan Colony, Narsingi, Hyderabad 500075, India
| | - Sumesh P Thampi
- Rudolf Peierls Centre for Theoretical Physics, 1 Keble Road, Oxford OX1 3NP, United Kingdom
| | - Rama Govindarajan
- Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research, 21 Brundavan Colony, Narsingi, Hyderabad 500075, India
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25
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MacDowell LG, Benet J, Katcho NA, Palanco JM. Disjoining pressure and the film-height-dependent surface tension of thin liquid films: new insight from capillary wave fluctuations. Adv Colloid Interface Sci 2014; 206:150-71. [PMID: 24351859 DOI: 10.1016/j.cis.2013.11.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 11/05/2013] [Accepted: 11/06/2013] [Indexed: 10/26/2022]
Abstract
In this paper we review simulation and experimental studies of thermal capillary wave fluctuations as an ideal means for probing the underlying disjoining pressure and surface tensions, and more generally, fine details of the Interfacial Hamiltonian Model. We discuss recent simulation results that reveal a film-height-dependent surface tension not accounted for in the classical Interfacial Hamiltonian Model. We show how this observation may be explained bottom-up from sound principles of statistical thermodynamics and discuss some of its implications.
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26
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Thiele U. Patterned deposition at moving contact lines. Adv Colloid Interface Sci 2014; 206:399-413. [PMID: 24331374 DOI: 10.1016/j.cis.2013.11.002] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Revised: 11/07/2013] [Accepted: 11/07/2013] [Indexed: 01/09/2023]
Abstract
When a simple or complex liquid recedes from a smooth solid substrate it often leaves a homogeneous or structured deposit behind. In the case of a receding non-volatile pure liquid the deposit might be a liquid film or an arrangement of droplets depending on the receding speed of the meniscus and the wetting properties of the system. For complex liquids with volatile components as, e.g., polymer solutions and particle or surfactant suspensions, the deposit might be a homogeneous or structured layer of solute--with structures ranging from line patterns that can be orthogonal or parallel to the receding contact line via hexagonal or square arrangements of drops to complicated hierarchical structures. We review a number of recent experiments and modelling approaches with a particular focus on mesoscopic hydrodynamic long-wave models. The conclusion highlights open question and speculates about future developments.
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Affiliation(s)
- Uwe Thiele
- Department of Mathematical Sciences, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK; Institut für Theoretische Physik, Westfälische Wilhelms-Universität Münster, Wilhelm Klemm Str. 9, D-48149 Münster, Germany.
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27
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Wetting-dewetting films: the role of structural forces. Adv Colloid Interface Sci 2014; 206:207-21. [PMID: 24035126 DOI: 10.1016/j.cis.2013.08.005] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 08/08/2013] [Accepted: 08/19/2013] [Indexed: 11/21/2022]
Abstract
The liquid wetting and dewetting of solids are ubiquitous phenomena that occur in everyday life. Understanding the nature of these phenomena is beneficial for research and technological applications. However, despite their importance, the phenomena are still not well understood because of the nature of the substrate's surface energy non-ideality and dynamics. This paper illustrates the mechanisms and applications of liquid wetting and dewetting on hydrophilic and hydrophobic substrates. We discuss the classical understanding and application of wetting and film stability criteria based on the Frumkin-Derjaguin disjoining pressure model. The roles of the film critical thickness and capillary pressure on the film instability based on the disjoining pressure isotherm are elucidated, as are the criteria for stable and unstable wet films. We consider the film area in the model for the film stability and the applicable experiments. This paper also addresses the two classic film instability mechanisms for suspended liquid films based on the conditions of the free energy criteria originally proposed by de Vries (nucleation hole formation) and Vrij-Scheludko (capillary waves vs. van der Waals forces) that were later adapted to explain dewetting. We include a discussion of the mechanisms of nanofilm wetting and dewetting on a solid substrate based on nanoparticles' tendency to form a 2D layer and 2D inlayer in the film under the wetting film's surface confinement. We also present our view on the future of wetting-dewetting modeling and its applications in developing emerging technologies. We believe the review and analysis presented here will benefit the current and future understanding of the wetting-dewetting phenomena, as well as aid in the development of novel products and technologies.
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28
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Nguyen TD, Carrillo JMY, Matheson MA, Brown WM. Rupture mechanism of liquid crystal thin films realized by large-scale molecular simulations. NANOSCALE 2014; 6:3083-3096. [PMID: 24264516 DOI: 10.1039/c3nr05413f] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The ability of liquid crystal (LC) molecules to respond to changes in their environment makes them an interesting candidate for thin film applications, particularly in bio-sensing, bio-mimicking devices, and optics. Yet the understanding of the (in)stability of this family of thin films has been limited by the inherent challenges encountered by experiment and continuum models. Using unprecedented large-scale molecular dynamics (MD) simulations, we address the rupture origin of LC thin films wetting a solid substrate at length scales similar to those in experiment. Our simulations show the key signatures of spinodal instability in isotropic and nematic films on top of thermal nucleation, and importantly, for the first time, evidence of a common rupture mechanism independent of initial thickness and LC orientational ordering. We further demonstrate that the primary driving force for rupture is closely related to the tendency of the LC mesogens to recover their local environment in the bulk state. Our study not only provides new insights into the rupture mechanism of liquid crystal films, but also sets the stage for future investigations of thin film systems using peta-scale molecular dynamics simulations.
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Affiliation(s)
- Trung Dac Nguyen
- National Center for Computational Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
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29
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Dey M, Bandyopadhyay D, Sharma A, Qian S, Joo SW. Charge Leakage Mediated Pattern Miniaturization in the Electric Field Induced Instabilities of an Elastic Membrane. Ind Eng Chem Res 2014. [DOI: 10.1021/ie500378k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mohar Dey
- School
of Mechanical Engineering, Yeungnam University, Gyeongsan 712749, South Korea
| | - Dipankar Bandyopadhyay
- Department
of Chemical Engineering, Indian Institute of Technology Guwahati, 781039, Assam, India
- Centre
for Nanotechnology, Indian Institute of Technology Guwahati, 781039, Assam, India
| | - Ashutosh Sharma
- Department
of Chemical Engineering, Indian Institute of Technology Kanpur, UP 208016, India
| | - Shizhi Qian
- Department
of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529, United States
| | - Sang Woo Joo
- School
of Mechanical Engineering, Yeungnam University, Gyeongsan 712749, South Korea
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30
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Nguyen TD, Fuentes-Cabrera M, Fowlkes JD, Rack PD. Coexistence of spinodal instability and thermal nucleation in thin-film rupture: insights from molecular levels. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:032403. [PMID: 24730848 DOI: 10.1103/physreve.89.032403] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Indexed: 06/03/2023]
Abstract
Despite extensive investigation using hydrodynamic models and experiments over the past decades, there remain open questions regarding the origin of the initial rupture of thin liquid films. One of the reasons that makes it difficult to identify the rupture origin is the coexistence of two dewetting mechanisms, namely, thermal nucleation and spinodal instability, as observed in many experimental studies. Using a coarse-grained model and large-scale molecular dynamics simulations, we are able to characterize the very early stage of dewetting in nanometer-thick liquid-metal films wetting a solid substrate. We observe the features characteristic of both spinodal instability and thermal nucleation in the spontaneously dewetting films and show that these two macroscopic mechanisms share a common origin at molecular levels.
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Affiliation(s)
- Trung Dac Nguyen
- National Center for Computational Sciences, Oak Ridge National Laboratory, Tennessee 37831
| | - Miguel Fuentes-Cabrera
- Center for Nanophase and Materials Science, Computer Science and Mathematics Division, Oak Ridge National Laboratory, Tennessee 37831 and Center for Nanophase and Materials Science, Oak Ridge National Laboratory, Tennessee 37831
| | - Jason D Fowlkes
- Center for Nanophase and Materials Science, Computer Science and Mathematics Division, Oak Ridge National Laboratory, Tennessee 37831
| | - Philip D Rack
- Center for Nanophase and Materials Science, Oak Ridge National Laboratory, Tennessee 37831 and Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996
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31
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Zhao D, Peng J, Tang X, Zhang D, Qiu X, Yang Y, Wang Y, Zhang M, Guan L, Cao T. Charge-induced local dewetting on polymer electrets studied by atomic force microscopy. SOFT MATTER 2013; 9:9702-9708. [PMID: 26029779 DOI: 10.1039/c3sm51997j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Polymer electrets are one of the most important series of electrets, which are widely used both in academic research and industrial applications. The effect of trapped charges on dielectric properties of the polymer electret is critical for more intelligent utilization of these materials. Herein we report the charge-induced polymer relaxation reflected by the local dewetting of the polymer electrets with charge patterns. Because the difference in charge-induced relaxation results in selective dewetting of thin polymer films, polymers in the charged areas are preferentially dewetted from the substrate compared with the neutral areas under heating or solvent annealing, leading to the appearance of hole arrays. Therefore, the effect of trapped charges on relaxation was also studied via monitoring the relaxation behaviours of homo-polymer and block copolymer films as well as measuring the mechanical properties of homo-polymers with charge patterns. These results demonstrate that the charge trapped in polymer electrets could accelerate relaxation and drive the dewetting process of thin polymer films.
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Affiliation(s)
- Dan Zhao
- Department of Chemistry, Renmin University of China, Beijing 100872, P.R. China
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32
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Thiele U, Todorova DV, Lopez H. Gradient dynamics description for films of mixtures and suspensions: dewetting triggered by coupled film height and concentration fluctuations. PHYSICAL REVIEW LETTERS 2013; 111:117801. [PMID: 24074118 DOI: 10.1103/physrevlett.111.117801] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Indexed: 06/02/2023]
Abstract
A thermodynamically consistent gradient dynamics model for the evolution of thin layers of liquid mixtures, solutions, and suspensions on solid substrates is presented which is based on a film-height- and mean-concentration-dependent free energy functional. It is able to describe a large variety of structuring processes, including coupled dewetting and decomposition processes. As an example, the model is employed to investigate the dewetting of thin films of liquid mixtures and suspensions under the influence of effective long-range van der Waals forces that depend on solute concentration. The occurring fluxes are discussed, and it is shown that spinodal dewetting may be triggered through the coupling of film height and concentration fluctuations. Fully nonlinear calculations provide the time evolution and resulting steady film height and concentration profiles.
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Affiliation(s)
- Uwe Thiele
- Department of Mathematical Sciences, Loughborough University, Loughborough, Leicestershire LE11 3TU, United Kingdom
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33
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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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34
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Bae J, Park SJ, Kwon OS, Jang J. A unique embossed carbon layer from induced domain alignment in a block copolymer thin film under an electric field. Chem Commun (Camb) 2013; 49:5456-8. [PMID: 23660739 DOI: 10.1039/c3cc42159g] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A unique embossed carbon surface with regionally heterogeneous properties is constructed via carbonization of a polyacrylonitrile-b-poly(methyl methacrylate) (PAN-b-PMMA) block copolymer thin film precursor self-assembled under an external electric field. The PAN-b-PMMA block copolymer generates a thin surface having microdomains with alternating PAN-PMMA compositions different from that of the matrix when the microdomain alignment is induced under an electric field due to the difference in dielectric susceptibilities between two blocks.
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Affiliation(s)
- Joonwon Bae
- Department of Applied Chemistry, Dongduk Women's University, Seoul, 136-714, Republic of Korea.
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35
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Tretyakov N, Müller M, Todorova D, Thiele U. Parameter passing between molecular dynamics and continuum models for droplets on solid substrates: The static case. J Chem Phys 2013; 138:064905. [DOI: 10.1063/1.4790581] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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36
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Hens A, Mondal K, Bandyopadhyay D. Self-organized pathways to nanopatterns exploiting the instabilities of ultrathin confined bilayers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 87:022405. [PMID: 23496524 DOI: 10.1103/physreve.87.022405] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 12/02/2012] [Indexed: 06/01/2023]
Abstract
Self-organized interfacial instabilities of an ultrathin bilayer confined between a pair of rigid surfaces is explored. The bilayers are classified based on the macroscopic dewetting behaviors of the liquid films sandwiched between a pair of confining surfaces having surface energy higher or lower than the liquid films. Linear and nonlinear analyses employing the governing equations originating from the continuum description together with molecular dynamics (MD) simulations unveil the salient spatiotemporal features of the dewetting process. The study uncovers that, under the destabilizing influence of the intermolecular interactions, the interface of a confined bilayer can deform into interesting embedded and encapsulated patterns with nanoscale periodicity. The continuum and MD simulations collectively show the detailed route to dewetting starting from the formation of holes in the early stage, their growth to achieve equilibrium contact angle at the intermediate phase, and then to evolve into the equilibrium morphologies at the later stage. Examples are shown where the length and the time scales of the simulated nanostructures from both the continuum and MD approaches are found to agree with the same obtained from the linear stability analysis. We also highlight the deviations that are observed in the continuum and MD approaches. The study confirms that the reduced stabilizing interfacial tension at the liquid-liquid interface together with enhanced intermolecular interaction because of the thinness of the layers can be an alternative strategy for pattern miniaturization exploiting the instabilities of a thin confined bilayer. Further, the study shows that use of topographical patterns on the bounding surfaces can impose periodic order to the holes, droplets, columns, and channels, which can find important applications in the diverse areas of nanotechnology.
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Affiliation(s)
- Abhiram Hens
- Micro System Technology Laboratory, CSIR - Central Mechanical Engineering Research Institute, Durgapur-713209, India
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37
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Mondal K, Kumar P, Bandyopadhyay D. Electric field induced instabilities of thin leaky bilayers: Pathways to unique morphologies and miniaturization. J Chem Phys 2013; 138:024705. [DOI: 10.1063/1.4773857] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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38
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Gomba JM, Perazzo CA. Closed-form expression for the profile of partially wetting two-dimensional droplets under gravity. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 86:056310. [PMID: 23214879 DOI: 10.1103/physreve.86.056310] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Revised: 09/26/2012] [Indexed: 06/01/2023]
Abstract
Analytical solutions for the shape of both hanging and sitting droplets under the effects of gravity and surface tension are presented. The modeling also includes the action of molecular forces arising between the liquid and the substrate, which are responsible for the formation of a stable nanometric film in the region close to the droplet contact line. The shape of the droplet is completely described by an analytical solution that also accounts for the pancake-shaped droplets as a limiting case. We find expressions that relate microscopic and nanoscopic aspects, such as the strengths of the molecular forces and the thickness of the nanometric film, to macroscopic quantities, such as the cross-sectional area and the width of the droplet. We study the effect of gravity on the contact angle and find that for small droplets the contact angle follows a power law with the droplet's size. For sitting droplets we find that the there is an upper limit for the value of the gravity.
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Affiliation(s)
- J M Gomba
- Department of Mechanical Engineering, University of California, Santa Barbara, California 19327, USA.
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39
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Checco A, Ocko BM, Tasinkevych M, Dietrich S. Stability of thin wetting films on chemically nanostructured surfaces. PHYSICAL REVIEW LETTERS 2012; 109:166101. [PMID: 23215094 DOI: 10.1103/physrevlett.109.166101] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Indexed: 06/01/2023]
Abstract
The morphology and stability of thin volatile wetting films on model chemically patterned surfaces composed of periodic arrays of alternating completely and partially wettable nanostripes are investigated. The equilibrium film morphology is recorded as a function of undersaturation using noncontact atomic force microscopy. Films spanning the entire pattern are found to be stable only for thicknesses in excess of a critical value, h(c), whereas thinner films spontaneously dewet the partially wettable regions of the substrate. The critical thickness h(c) increases linearly with the width of the partially wettable stripes in good agreement with an interface displacement model derived from microscopic density functional theory. These results provide detailed insights into the dewetting of thin films driven by competing intermolecular forces.
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Affiliation(s)
- A Checco
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
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40
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Dey M, Bandyopadhyay D, Sharma A, Qian S, Joo SW. Electric-field-induced interfacial instabilities of a soft elastic membrane confined between viscous layers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 86:041602. [PMID: 23214594 DOI: 10.1103/physreve.86.041602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Indexed: 06/01/2023]
Abstract
We explore the electric-field-induced interfacial instabilities of a trilayer composed of a thin elastic film confined between two viscous layers. A linear stability analysis (LSA) is performed to uncover the growth rate and length scale of the different unstable modes. Application of a normal external electric field on such a configuration can deform the two coupled elastic-viscous interfaces either by an in-phase bending or an antiphase squeezing mode. The bending mode has a long-wave nature, and is present even at a vanishingly small destabilizing field. In contrast, the squeezing mode has finite wave-number characteristics and originates only beyond a threshold strength of the electric field. This is in contrast to the instabilities of the viscous films with multiple interfaces where both modes are found to possess long-wave characteristics. The elastic film is unstable by bending mode when the stabilizing forces due to the in-plane curvature and the elastic stiffness are strong and the destabilizing electric field is relatively weak. In comparison, as the electric field increases, a subdominant squeezing mode can also appear beyond a threshold destabilizing field. A dominant squeezing mode is observed when the destabilizing field is significantly strong and the elastic films are relatively softer with lower elastic modulus. In the absence of liquid layers, a free elastic film is also found to be unstable by long-wave bending and finite wave-number squeezing modes. The LSA asymptotically recovers the results obtained by the previous formulations where the membrane bending elasticity is approximately incorporated as a correction term in the normal stress boundary condition. Interestingly, the presence of a very weak stabilizing influence due to a smaller interfacial tension at the elastic-viscous interfaces opens up the possibility of fabricating submicron patterns exploiting the instabilities of a trilayer.
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Affiliation(s)
- Mohar Dey
- School of Mechanical Engineering, Yeungnam University, Gyeongsan 712-749, South Korea
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Zhang J, Hu X, Zhang J, Cui Y, Yuan C, Ge H, Chen Y, Wu W, Xia Q. A fast thermal-curing nanoimprint resist based on cationic polymerizable epoxysiloxane. NANOSCALE RESEARCH LETTERS 2012; 7:380. [PMID: 22775987 PMCID: PMC3496635 DOI: 10.1186/1556-276x-7-380] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Accepted: 06/25/2012] [Indexed: 05/29/2023]
Abstract
We synthesized a series of epoxysiloxane oligomers with controllable viscosity and polarity and developed upon them a thermal-curable nanoimprint resist that was cross-linked in air at 110°C within 30 s if preexposed to UV light. The oligomers were designed and synthesized via hydrosilylation of 4-vinyl-cyclohexane-1,2-epoxide with poly(methylhydrosiloxane) with tunable viscosity, polarity, and cross-linking density. The resist exhibits excellent chemical and physical properties such as insensitivity toward oxygen, strong mechanical strength, and high etching resistance. Using this resist, nanoscale patterns of different geometries with feature sizes as small as 30 nm were fabricated via a nanoimprint process based on UV-assisted thermal curing. The curing time for the resist was on the order of 10 s at a moderate temperature with the help of UV light preexposure. This fast thermal curing speed was attributed to the large number of active cations generated upon UV exposure that facilitated the thermal polymerization process.
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Affiliation(s)
- Jizong Zhang
- Department of Materials Science and Engineering, College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210093, People's Republic of China
| | - Xin Hu
- Department of Materials Science and Engineering, College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210093, People's Republic of China
| | - Jian Zhang
- Department of Materials Science and Engineering, College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210093, People's Republic of China
| | - Yushang Cui
- Department of Materials Science and Engineering, College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210093, People's Republic of China
| | - Changsheng Yuan
- Department of Materials Science and Engineering, College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210093, People's Republic of China
| | - Haixiong Ge
- Department of Materials Science and Engineering, College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210093, People's Republic of China
| | - Yanfeng Chen
- Department of Materials Science and Engineering, College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210093, People's Republic of China
| | - Wei Wu
- Hewlett-Packard Laboratories, 1501 Page Mill Road, Palo Alto, CA, 94304, USA
| | - Qiangfei Xia
- Department of Electrical and Computer Engineering, University of Massachusetts, Amherst, MA, 01003, USA
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Robbins MJ, Archer AJ, Thiele U. Modelling the evaporation of thin films of colloidal suspensions using dynamical density functional theory. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:415102. [PMID: 21952487 DOI: 10.1088/0953-8984/23/41/415102] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Recent experiments have shown that various structures may be formed during the evaporative dewetting of thin films of colloidal suspensions. Nanoparticle deposits of strongly branched 'flower-like', labyrinthine and network structures are observed. They are caused by the different transport processes and the rich phase behaviour of the system. We develop a model for the system, based on a dynamical density functional theory, which reproduces these structures. The model is employed to determine the influences of the solvent evaporation and of the diffusion of the colloidal particles and of the liquid over the surface. Finally, we investigate the conditions needed for 'liquid-particle' phase separation to occur and discuss its effect on the self-organized nanostructures.
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Affiliation(s)
- M J Robbins
- Department of Mathematical Sciences, Loughborough University, Leicestershire LE11 3TU, UK
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Shanahan MER, Sefiane K, Moffat JR. Dependence of volatile droplet lifetime on the hydrophobicity of the substrate. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:4572-4577. [PMID: 21434625 DOI: 10.1021/la200437s] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In this Article, we demonstrate the dependence of the lifetime of a volatile droplet on the hydrophobicity of the substrate. Ethanol droplets placed on the molecularly smooth surfaces of three polymers, applied to substrates by spin-coating, showed distinct types of behavior depending on the hydrophobicity of the latter. High contact angles, θ, lead to fairly regular recession of the triple line during liquid evaporation at essentially constant θ, whereas low contact angle caused pinning, θ decreasing with time. The latter case leads to shorter drop lifetimes.
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Affiliation(s)
- M E R Shanahan
- Université de Bordeaux, Institut de Mécanique et d'Ingénierie de Bordeaux (I2M), CNRS UMR 5295, Bât. A4, Cours de la Libération, 33405 TALENCE Cedex, France
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Frastia L, Archer AJ, Thiele U. Dynamical model for the formation of patterned deposits at receding contact lines. PHYSICAL REVIEW LETTERS 2011; 106:077801. [PMID: 21405542 DOI: 10.1103/physrevlett.106.077801] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Indexed: 05/30/2023]
Abstract
We describe the formation of deposition patterns that are observed in many different experiments where a three-phase contact line of a volatile nanoparticle suspension or polymer solution recedes. A dynamical model based on a long-wave approximation predicts the deposition of irregular and regular line patterns due to self-organized pinning-depinning cycles corresponding to a stick-slip motion of the contact line. We analyze how the line pattern properties depend on the evaporation rate and solute concentration.
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Affiliation(s)
- Lubor Frastia
- Department of Mathematical Sciences, Loughborough University, Leicestershire, United Kingdom
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Patra A, Bandyopadhyay D, Tomar G, Sharma A, Biswas G. Instability and dewetting of ultrathin solid viscoelastic films on homogeneous and heterogeneous substrates. J Chem Phys 2011; 134:064705. [DOI: 10.1063/1.3554748] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Patel AJ, Rappl TJ, Balsara NP. Similarity of the signatures of the initial stages of phase separation in metastable and unstable polymer blends. PHYSICAL REVIEW LETTERS 2011; 106:035702. [PMID: 21405281 DOI: 10.1103/physrevlett.106.035702] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Revised: 12/09/2010] [Indexed: 05/30/2023]
Abstract
Time-resolved small angle neutron scattering was used to probe the initial stages of liquid-liquid phase separation in both critical and off-critical binary polymer blends, and the critical (q(c)) and most probable (q(m)) wave vectors were identified for several quench depths. For the critical blend, the Cahn-Hilliard-Cook theory provides a framework for analyzing the data and explains the observed decrease in q(m) with time. For the off-critical blend, q(m) is independent of quench time, regardless of whether the quench is metastable or unstable.
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Affiliation(s)
- Amish J Patel
- Department of Chemical Engineering, University of California, Berkeley, California 94720, USA
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Beltrame P, Knobloch E, Hänggi P, Thiele U. Rayleigh and depinning instabilities of forced liquid ridges on heterogeneous substrates. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 83:016305. [PMID: 21405772 DOI: 10.1103/physreve.83.016305] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Indexed: 05/30/2023]
Abstract
Depinning of two-dimensional liquid ridges and three-dimensional drops on an inclined substrate is studied within the lubrication approximation. The structures are pinned to wetting heterogeneities arising from variations of the strength of the short-range contribution to the disjoining pressure. The case of a periodic array of hydrophobic stripes transverse to the slope is studied in detail using a combination of direct numerical simulation and branch-following techniques. Under appropriate conditions the ridges may either depin and slide downslope as the slope is increased, or first break up into drops via a transverse instability, prior to depinning. The different transition scenarios are examined together with the stability properties of the different possible states of the system.
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Affiliation(s)
- Philippe Beltrame
- UMR EmmaH 1114, Département de Physique, Université d'Avignon, F-84000 Avignon, France.
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Neogi P. Labyrinthine instability in thin liquid films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:415102. [PMID: 21386592 DOI: 10.1088/0953-8984/22/41/415102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
When a thin liquid film on a solid surface has a thickness corresponding to a particular part the spinodal region of the disjoining pressure versus thickness isotherm, the film breaks down. One of the patterns that emerges on the breakdown has been referred to as wavy instability. It is compared here to the labyrinthine instability seen in magnetic films. The system is modeled following the procedure used in magnetic systems, and the pattern of wavy instability is broken down into a curved thick-thin film in equilibrium with a flat thin-thin film of constant thickness. Minimization of free energy leads to expressions for various length scales that characterize the system. Comparisons with published experimental results on nematic liquid crystals for a number of very different features are satisfactory. They include film thicknesses in the bulk at equilibrium where the capillary pressure is not zero, and is determined as a part of the solution, as well as film thicknesses in the ledge where the capillary pressure is zero. Stability analysis shows that the system is unstable in both directions with some qualifiers. A model is proposed in the form of a tiled structure to explain the labyrinthine form.
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Affiliation(s)
- P Neogi
- Chemical and Biological Engineering, Missouri University of Science and Technology, Rolla, MO 65409-1230, USA.
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