201
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Léonforte F, Servantie J, Pastorino C, Müller M. Molecular transport and flow past hard and soft surfaces: computer simulation of model systems. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:184105. [PMID: 21508476 DOI: 10.1088/0953-8984/23/18/184105] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The equilibrium and flow of polymer films and drops past a surface are characterized by the interface and surface tensions, viscosity, slip length and hydrodynamic boundary position. These parameters of the continuum description are extracted from molecular simulations of coarse-grained models. Hard, corrugated substrates are modelled by a Lennard-Jones solid while polymer brushes are studied as prototypes of soft, deformable surfaces. Four observations are discussed. (i) If the surface becomes strongly attractive or is coated with a brush, the Navier boundary condition fails to describe the effect of the surface independently of the strength and type of the flow. This failure stems from the formation of a boundary layer with an effective, higher viscosity. (ii) In the case of brush-coated surfaces, flow induces a cyclic, tumbling motion of the tethered chain molecules. Their collective motion gives rise to an inversion of the flow in the vicinity of the grafting surfaces and leads to strong, non-Gaussian fluctuations of the molecular orientations. The flow past a polymer brush cannot be described by Brinkman's equation. (iii) The hydrodynamic boundary condition is an important parameter for predicting the motion of polymer droplets on a surface under the influence of an external force. Their steady-state velocity is dictated by a balance between the power that is provided by the external force and the dissipation. If there is slippage at the liquid-solid interface, the friction at the solid-liquid interface and the viscous dissipation of the flow inside the drop will be the dominant dissipation mechanisms; dissipation at the three-phase contact line appears to be less important on a hard surface. (iv) On a soft, deformable substrate like a polymer brush, we observe a lifting-up of the three-phase contact line. Controlling the grafting density and the incompatibility between the brush and the polymer liquid we can independently tune the softness of the surface and the contact angle and thereby identify the parameters for maximizing the deformation at the three-phase contact.
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Affiliation(s)
- F Léonforte
- Institut für Theoretische Physik, Georg-August-Universität, 37077 Göttingen, Germany
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202
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Seemann R, Brinkmann M, Herminghaus S, Khare K, Law BM, McBride S, Kostourou K, Gurevich E, Bommer S, Herrmann C, Michler D. Wetting morphologies and their transitions in grooved substrates. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:184108. [PMID: 21508471 DOI: 10.1088/0953-8984/23/18/184108] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
When exposed to a partially wetting liquid, many natural and artificial surfaces equipped with complex topographies display a rich variety of liquid interfacial morphologies. In the present article, we focus on a few simple paradigmatic surface topographies and elaborate on the statics and dynamics of the resulting wetting morphologies. It is demonstrated that the spectrum of wetting morphologies increases with increasing complexity of the groove structure. On elastically deformable substrates, additional structures in the liquid morphologies can be observed, which are caused by deformations of the groove geometry in the presence of capillary forces. The emergence of certain liquid morphologies in grooves can be actively controlled by changes in wettability and geometry. For electrically conducting solid substrates, the apparent contact angle can be varied by electrowetting. This allows, depending on groove geometry, a reversible or irreversible transport of liquid along surface grooves. In the case of irreversible liquid transport in triangular grooves, the dynamics of the emerging instability is sensitive to the apparent hydrodynamic slip at the substrate. On elastic substrates, the geometry can be varied in a straightforward manner by stretching or relaxing the sample. The imbibition velocity in deformable grooves is significantly reduced compared to solid grooves, which is a result of the microscopic deformation of the elastic groove material close to the three phase contact line.
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Affiliation(s)
- Ralf Seemann
- Experimental Physics, Saarland University, D-66123 Saarbrücken, Germany.
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203
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Wong HC, Cabral JT. Mechanism and Kinetics of Fullerene Association in Polystyrene Thin Film Mixtures. Macromolecules 2011. [DOI: 10.1021/ma2004458] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Him Cheng Wong
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, U.K
| | - João T. Cabral
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, U.K
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204
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Siretanu I, Chapel JP, Drummond C. Water-ions induced nanostructuration of hydrophobic polymer surfaces. ACS NANO 2011; 5:2939-2947. [PMID: 21434645 DOI: 10.1021/nn103564e] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
When hydrophobic surfaces are in contact with water in ambient conditions a layer of reduced density is present at the interface, preventing the intimate contact between the two phases. Reducing the extent of this layer by degassing the water can have remarkable implications for the interaction between the two phases. The enhanced proximity between a hydrophobic polymer film and an aqueous solution can induce a self-assembled nanostructure on the solid surface through the development of an electro-hydrodynamic instability, due to the adsorption of the water-ions (hydronium and hydroxyl) at the interface. The self-assembled structure spontaneously relaxes back to the original flat morphology after few weeks at room temperature. This instability and the self-assembled structure are controlled by the hydrophobic surface charge, which is determined by the pH of the aqueous phase, and by the amount of gas dissolved. This effect can be easily adjusted to modify different hydrophobic polymeric substrates at the submicrometer level, opening pathways for producing controlled patterns at the nanoscale in a single simple waterborne step.
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Affiliation(s)
- Igor Siretanu
- Université de Bordeaux, Centre de Recherche Paul Pascal, UPR8641 CNRS, Avenue Schweitzer, 33600 Pessac Cedex, France
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205
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Rubinstein BY, Leshansky AM. Rupture of thin liquid films: generalization of weakly nonlinear theory. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 83:031603. [PMID: 21517509 DOI: 10.1103/physreve.83.031603] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2010] [Indexed: 05/30/2023]
Abstract
In this paper, we investigate the rupture dynamics of thin liquid films driven by intermolecular forces via weakly nonlinear bifurcation analysis. The dynamic equations governing slow dynamics of the perturbation amplitude of the near-critical mode corresponding to several models describing the evolution of thin liquid films in different physical situations appear to have the same structure. When antagonistic (attractive and repulsive) molecular forces are considered, nonlinear saturation of the instability becomes possible, while the boundary of this supercritical bifurcation is determined solely by the form of the intermolecular potential. The rupture time estimate obtained in closed form shows an excellent agreement with the results of the previously reported numerical simulations of the strongly nonlinear coupled evolution equations upon fitting the amplitude of the small initial perturbation. We further extend the weakly nonlinear analysis of the film dynamics and apply the Galerkin approximation to derive the amplitude equation(s) governing the dynamics of the fastest growing linear mode far from the instability threshold. The comparison of the rupture time derived from this theory with the results of numerical simulations of the original nonlinear evolution equations shows a very good agreement without any adjustable parameters.
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Affiliation(s)
- B Y Rubinstein
- Stowers Institute for Medical Research, 1000 E. 50th St., Kansas City, Missouri 64110, USA
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206
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207
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Sun Y, Shull KR, Walko DA, Wang J. Thickness-dependent autophobic dewetting of thin polymer films on coated substrates. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:201-208. [PMID: 21117671 DOI: 10.1021/la103774d] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We demonstrate that the wetting behavior of a thin liquid film, poly(4-bromostyrene) (PBrS), on top of a solid substrate may be effectively controlled with the insertion of a secondary liquid film, poly(4-vinyl pyridine) (P4VP), underneath the primary film. This secondary film remains stable under all conditions, and can be viewed as an extension of the substrate itself. On the basis of results from X-ray standing waves generated via total external reflection from an X-ray mirror, time-of-flight secondary ion mass spectroscopy, optical microscopy, and atomic force microscopy, we construct the full Helmholtz free energy versus PBrS thickness curve using existing theories that account for both long- and short-range interactions. The form of the free energy curve, which contains an inflection point and an absolute minimum at a nonzero PBrS thickness, accurately reflects our observation that thick PBrS films undergo autophobic dewetting on top of the stable P4VP, while sufficiently thin PBrS films remain stable. The thickness of the autophobic wetting layer is controlled by the range of the repulsive interaction between the film and the substrate, and is found to be ∼4 nm for the PBrS/P4VP interface.
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Affiliation(s)
- Yan Sun
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
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208
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Strobel S, Kirkendall C, Chang JB, Berggren KK. Sub-10 nm structures on silicon by thermal dewetting of platinum. NANOTECHNOLOGY 2010; 21:505301. [PMID: 21098926 DOI: 10.1088/0957-4484/21/50/505301] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A study of the dewetting behavior of platinum-thin-films on silicon was carried out to determine how variation of dewetting parameters affects the evolution of film morphology and to pinpoint which parameters yielded the smallest, most circular features. Platinum film thickness as well as dewetting time and temperature were varied and the film morphology characterized by means of scanning electron microscopy (SEM) analysis. Two different pathways of dewetting predicted in the literature (Vrij 1966 Discuss. Faraday Soc. 42 23, Becker et al 2003 Nat. Mater. 2 59-63) were observed. Depending on the initial criteria, restructuring of the film occurred via hole or droplet formation. With increased annealing time, a transition from an intermediate network structure to separated islands occurred. In addition, the formation of multilayered films, silicide crystals and nanowires occurred for certain parameters. Nevertheless, the dewetting behavior witnessed could be related to physical processes. Droplets with a mean diameter of 9 nm were formed by using a 1.5 nm thick platinum film annealed at 800 °C for 30 s. To demonstrate the suitability of the annealed films for further processing, we then used the dewetted films as masks for reactive ion etching to transfer the pattern into the silicon substrate, forming tapered nanopillars.
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Affiliation(s)
- Sebastian Strobel
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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209
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Rathfon JM, Cohn RW, Crosby AJ, Tew GN. Hole Nucleation and Growth in Free-Standing Polystyrene Ultrathin Films. Macromolecules 2010. [DOI: 10.1021/ma1020227] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jeremy M. Rathfon
- Department of Polymer Science and Engineering, University of Massachusetts Amherst, 120 Governors Drive, Amherst, Massachusetts 01003, United States
- ElectroOptics Research Institute and Nanotechnology Center, University of Louisville, Louisville, Kentucky 40292, United States
| | - Robert W. Cohn
- ElectroOptics Research Institute and Nanotechnology Center, University of Louisville, Louisville, Kentucky 40292, United States
| | - Alfred J. Crosby
- Department of Polymer Science and Engineering, University of Massachusetts Amherst, 120 Governors Drive, Amherst, Massachusetts 01003, United States
| | - Gregory N. Tew
- Department of Polymer Science and Engineering, University of Massachusetts Amherst, 120 Governors Drive, Amherst, Massachusetts 01003, United States
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210
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Verma A, Sharma A. Enhanced self-organized dewetting of ultrathin polymer films under water-organic solutions: fabrication of sub-micrometer spherical lens arrays. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2010; 22:5306-5309. [PMID: 20872412 DOI: 10.1002/adma.201002768] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Affiliation(s)
- Ankur Verma
- Department of Chemical Engineering & DST unit on Nanosciences, Indian Institute of Technology Kanpur, Kanpur 208016, India
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211
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Rueda DR, Hernández JJ, García-Gutiérrez MC, Ezquerra TA, Soccio M, Lotti N, Munari A, Perlich J, Serna R. Flat-on lamellae in spin-coated, stable films of poly(propylene azelate). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:17540-17545. [PMID: 20883025 DOI: 10.1021/la1030153] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Thin films (5-500 nm thick) of the linear aliphatic polyester (3,7) poly(propylene azelate) (PPAz) were prepared by spin-coating of CHCl(3) polymer solutions with different polymer concentrations. The morphology and structure of the spin-coated thin films were investigated by atomic force microscopy (AFM) and by grazing incidence wide-angle X-ray scattering (GIWAXS) techniques. AFM revealed the continuous nature of the flat, spherulitic films which are stable against dewetting even for polymer coatings as thin as 15 nm. GIWAXS patterns revealed a high crystal orientation of the films. A sharp reflection on the meridian whose spacing is related to the polymer chain unit length (c-axis) supports the presence of flat-on lamellae morphology in the whole range of film thicknesses investigated. The flat-on lamellae morphology is also supported by AFM images. A triclinic unit cell with the c*-axis perpendicular to the substrate is proposed for PPAz. The repulsion of the long aliphatic spacer by the Si-substrate is invoked as the main reason for the flat-on morphology observed.
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Affiliation(s)
- D R Rueda
- Instituto de Estructura de la Materia, CSIC. Serrano 121, 28006 Madrid, Spain
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212
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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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213
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Thickett SC, Harris A, Neto C. Interplay between dewetting and layer inversion in poly(4-vinylpyridine)/polystyrene bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:15989-15999. [PMID: 20857967 DOI: 10.1021/la103078k] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We investigated the morphology and dynamics of the dewetting of metastable poly(4-vinylpyridine) (P4VP) thin films situated on top of polystyrene (PS) thin films as a function of the molecular weight and thickness of both films. We focused on the competition between the dewetting process, occurring as a result of unfavorable intermolecular interactions at the P4VP/PS interface, and layer inversion due to the lower surface energy of PS. By means of optical and atomic force microscopy (AFM), we observed how both the dynamics of the instability and the morphology of the emerging patterns depend on the ratio of the molecular weights of the polymer films. When the bottom PS layer was less viscous than the top P4VP layer (liquid-liquid dewetting), nucleated holes in the P4VP film typically stopped growing at long annealing times because of a combination of viscous dissipation in the bottom layer and partial layer inversion. Full layer inversion was achieved when the viscosity of the top P4VP layer was significantly greater (>10⁴) than the viscosity of the PS layer underneath, which is attributed to strongly different mobilities of the two layers. The density of holes produced by nucleation dewetting was observed for the first time to depend on the thickness of the top film as well as the polymer molecular weight. The final (completely dewetted) morphology of isolated droplets could be achieved only if the time frame of layer inversion was significantly slower than that of dewetting, which was characteristic of high-viscosity PS underlayers that allowed dewetting to fall into a liquid-solid regime. Assuming a simple reptation model for layer inversion occurring at the dewetting front, the observed surface morphologies could be predicted on the basis of the relative rates of dewetting and layer inversion.
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Affiliation(s)
- Stuart C Thickett
- School of Chemistry F11, The University of Sydney, NSW 2006, Australia
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214
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Schmitt Y, Hähl H, Gilow C, Mantz H, Jacobs K, Leidinger O, Bellion M, Santen L. Structural evolution of protein-biofilms: Simulations and experiments. BIOMICROFLUIDICS 2010; 4:32201. [PMID: 21045923 PMCID: PMC2967234 DOI: 10.1063/1.3488672] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2010] [Accepted: 08/23/2010] [Indexed: 05/15/2023]
Abstract
The control of biofilm formation is a challenging goal that has not been reached yet in many aspects. One unsolved question is the role of van der Waals forces and another is the importance of mutual interactions between the adsorbing and the adsorbed biomolecules ("critical crowding"). In this study, a combined experimental and theoretical approach is presented, which fundamentally probes both aspects. On three model proteins-lysozyme, α-amylase, and bovine serum albumin-the adsorption kinetics is studied experimentally. Composite substrates are used enabling a separation of the short- and the long-range forces. Although usually neglected, experimental evidence is given for the influence of van der Waals forces on the protein adsorption as revealed by in situ ellipsometry. The three proteins were chosen for their different conformational stabilities in order to investigate the influence of conformational changes on the adsorption kinetics. Monte Carlo simulations are used to develop a model for these experimental results by assuming an internal degree of freedom to represent conformational changes. The simulations also provide data on the distribution of adsorption sites. By in situ atomic force microscopy we can also test this distribution experimentally, which opens the possibility to, e.g., investigate the interactions between adsorbed proteins.
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215
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Chen Z, Dang XD, Gutacker A, Garcia A, Li H, Xu Y, Ying L, Nguyen TQ, Bazan GC. Reconstruction of Conjugated Oligoelectrolyte Electron Injection Layers. J Am Chem Soc 2010; 132:12160-2. [DOI: 10.1021/ja1056856] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Zhao Chen
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, Department of Materials, and Department of Physics, University of California, Santa Barbara, California 93106, and Macromolecular Chemistry Group and Institute for Polymer Technology, Bergische Universität Wuppertal, Gauss-Str. 20, D-42097 Wuppertal, Germany
| | - Xuan-Dung Dang
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, Department of Materials, and Department of Physics, University of California, Santa Barbara, California 93106, and Macromolecular Chemistry Group and Institute for Polymer Technology, Bergische Universität Wuppertal, Gauss-Str. 20, D-42097 Wuppertal, Germany
| | - Andrea Gutacker
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, Department of Materials, and Department of Physics, University of California, Santa Barbara, California 93106, and Macromolecular Chemistry Group and Institute for Polymer Technology, Bergische Universität Wuppertal, Gauss-Str. 20, D-42097 Wuppertal, Germany
| | - Andrew Garcia
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, Department of Materials, and Department of Physics, University of California, Santa Barbara, California 93106, and Macromolecular Chemistry Group and Institute for Polymer Technology, Bergische Universität Wuppertal, Gauss-Str. 20, D-42097 Wuppertal, Germany
| | - Huaping Li
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, Department of Materials, and Department of Physics, University of California, Santa Barbara, California 93106, and Macromolecular Chemistry Group and Institute for Polymer Technology, Bergische Universität Wuppertal, Gauss-Str. 20, D-42097 Wuppertal, Germany
| | - Yunhua Xu
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, Department of Materials, and Department of Physics, University of California, Santa Barbara, California 93106, and Macromolecular Chemistry Group and Institute for Polymer Technology, Bergische Universität Wuppertal, Gauss-Str. 20, D-42097 Wuppertal, Germany
| | - Lei Ying
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, Department of Materials, and Department of Physics, University of California, Santa Barbara, California 93106, and Macromolecular Chemistry Group and Institute for Polymer Technology, Bergische Universität Wuppertal, Gauss-Str. 20, D-42097 Wuppertal, Germany
| | - Thuc-Quyen Nguyen
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, Department of Materials, and Department of Physics, University of California, Santa Barbara, California 93106, and Macromolecular Chemistry Group and Institute for Polymer Technology, Bergische Universität Wuppertal, Gauss-Str. 20, D-42097 Wuppertal, Germany
| | - Guillermo C. Bazan
- Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, Department of Materials, and Department of Physics, University of California, Santa Barbara, California 93106, and Macromolecular Chemistry Group and Institute for Polymer Technology, Bergische Universität Wuppertal, Gauss-Str. 20, D-42097 Wuppertal, Germany
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216
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Mukherjee R, Das S, Das A, Sharma SK, Raychaudhuri AK, Sharma A. Stability and dewetting of metal nanoparticle filled thin polymer films: control of instability length scale and dynamics. ACS NANO 2010; 4:3709-3724. [PMID: 20560592 DOI: 10.1021/nn901912d] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We investigate the influence of gold nanoparticle addition on the stability, dewetting, and pattern formation in ultrathin polymer-nanoparticle (NP) composite films by examining the length and time scales of instability, morphology, and dynamics of dewetting. For these 10-50 nm thick (h) polystyrene (PS) thin films containing uncapped gold nanoparticles (diameter approximately 3-4 nm), transitions from complete dewetting to arrested dewetting to absolute stability were observed depending on the concentration of the particles. Experiments show the existence of three distinct stability regimes: regime 1, complete dewetting leading to droplet formation for nanoparticle concentration of 2% (w/w) or below; regime 2, partial dewetting leading to formation of arrested holes for NP concentrations in the range of 3-6%; and regime 3, complete inhibition of dewetting for NP concentrations of 7% and above. Major results are (a) length scale of instability, where lambdaH approximately hn remains unchanged with NP concentration in regime 1 (n approximately 2) but increases in regime 2 with a change in the scaling relation (n approximately 3-3.5); (b) dynamics of instability and dewetting becomes progressively sluggish with an increase in the NP concentration; (c) there are distinct regimes of dewetting velocity at low NP concentrations; (d) force modulation AFM, as well as micro-Raman analysis, shows phase separation and aggregation of the gold nanoparticles within each dewetted polymer droplet leading to the formation of a metal core-polymer shell morphology. The polymer shell could be removed by washing in a selective solvent, thus exposing an array of bare gold nanoparticle aggregates.
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Affiliation(s)
- Rabibrata Mukherjee
- Department of Chemical Engineering, Indian Institute of Technology Kharagpur, Pin 721 302, West Bengal, India
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217
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Wu Y, Fowlkes JD, Rack PD, Diez JA, Kondic L. On the breakup of patterned nanoscale copper rings into droplets via pulsed-laser-induced dewetting: competing liquid-phase instability and transport mechanisms. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:11972-11979. [PMID: 20578747 DOI: 10.1021/la1013818] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Nanolithographically patterned copper rings were synthesized, and the self-assembly of the rings into ordered nanoparticle/nanodrop arrays was accomplished via nanosecond pulsed laser heating above the melt threshold. The resultant length scale was correlated to the transport and instability growths that occur during the liquid lifetime of the melted copper rings. For 13-nm-thick rings, a change in the nanoparticle spacing with the ring width is attributed to a transition from a Raleigh-Plateau instability to a thin film instability because of competition between the cumulative transport and instability timescales. To explore the competition between instability mechanisms further, we carried out experiments with 7-nm-thick rings. In agreement with the theoretical predictions, these rings break up in both the azimuthal and radial directions, confirming that a simple hydrodynamic model captures the main features of the processes leading to the breakup.
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Affiliation(s)
- Yueying Wu
- Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996, USA
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218
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Wong HC, Cabral JT. Spinodal clustering in thin films of nanoparticle-polymer mixtures. PHYSICAL REVIEW LETTERS 2010; 105:038301. [PMID: 20867812 DOI: 10.1103/physrevlett.105.038301] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Revised: 05/18/2010] [Indexed: 05/29/2023]
Abstract
Thin supported polystyrene-C(60) fullerene mixtures annealed above their glass transition temperature develop spinodal surface undulations which depend on film thickness h(20-500 nm), polymer molecular mass M(w), temperature, and time t. The dominant wavelength λ ∼1-10 μm scales linearly with h and coarsening kinetics follow λ∼t{α}, with 0< α(h) < 1/3; the morphology eventually pins at long times. This spinodal surface excitation contrasts with dewetting suppression and film stability observed in low -M(w) polymers and results from the interplay of binary miscibility and fullerene substrate attraction.
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Affiliation(s)
- Him Cheng Wong
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, United Kingdom
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219
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Hernández JJ, Rueda DR, García-Gutiérrez MC, Nogales A, Ezquerra TA, Soccio M, Lotti N, Munari A. Structure and morphology of thin films of linear aliphatic polyesters prepared by spin-coating. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:10731-10737. [PMID: 20394389 DOI: 10.1021/la100959j] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Thin films, with thicknesses from 10 to 400 nm of linear aliphatic polyesters (X, Y), based on propylenediol (X = 3) and on dicarboxylic acid of different chain length (Y = 2, 3, and 4 CH(2) units) were prepared by spin coating of CHCl(3) polymer solutions with different polymer concentrations. Morphology and structure of the spin coated thin films were investigated by atomic force microscopy (AFM) and by grazing incidence X-ray scattering techniques at small, (GISAXS) and wide angles (GIWAXS). AFM revealed a strong dewetting for all three polymers for coatings thinner than 100 nm. The polymer films are clearly semicrystalline for thicknesses higher than 50 nm. GIWAXS of the thicker films revealed their oriented crystalline nature. An edge-on-lamellae morphology is clearly shown by the AFM-phase images even for relatively thin films. SAXS with the beam parallel to the sample plane also support the presence of lamellae perpendicular to the substrate. The use of a mu-beam helped to interpret the GIWAXS patterns and allowed to obtain oriented WAXS patterns from melt solidified filaments. Thus, a crystal chain packing is proposed for the three polymers and consequently the indexing of the observed reflections. Accordingly, the polymer chains lie parallel to the substrate being the bc plane of the monoclinic crystal unit cell parallel to the substrate.
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Affiliation(s)
- J J Hernández
- Instituto de Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid, Spain
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220
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Khanna R, Agnihotri NK, Vashishtha M, Sharma A, Jaiswal PK, Puri S. Kinetics of spinodal phase separation in unstable thin liquid films. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 82:011601. [PMID: 20866623 DOI: 10.1103/physreve.82.011601] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2010] [Revised: 05/04/2010] [Indexed: 05/29/2023]
Abstract
We study universality in the kinetics of spinodal phase separation in unstable thin liquid films, via simulations of the thin film equation. It is shown that, in addition to morphology and free energy, the number density of local maxima in the film profile can also be used to identify the early, late, and intermediate stages of spinodal phase separation. A universal curve between the number density of local maxima and rescaled time describes the kinetics of the early stage in d=2 and 3. The Lifshitz-Slyozov exponent of -1/3 describes the kinetics of the late stage in d=2 even in the absence of coexisting equilibrium phases.
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Affiliation(s)
- Rajesh Khanna
- Department of Chemical Engineering, Indian Institute of Technology Delhi, New Delhi 110016, India.
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221
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Bernardes JS, Rezende CA, Galembeck F. Morphology and self-arraying of SDS and DTAB dried on mica surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:7824-7832. [PMID: 20158224 DOI: 10.1021/la9046726] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Dewetting phenomena produce interesting patterns that may impart new properties to solid surfaces. Sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (DTAB) aqueous solutions, dried on mica surfaces under different drying conditions, undergo dewetting events forming structured deposits that were imaged by scanning electron microscopy (SEM), atomic force (AFM) and Kelvin force microscopy (KFM). Dry SDS, in most situations, displays long branched stripes formed due to fingering instability, while DTAB undergoes stick-slip motion forming patterns of parallel continuous or split stripes. In both systems, independently of drying conditions, surfactants pack forming lamellar structures, but with different orientations: SDS lamellae are aligned parallel to the substrate whereas DTAB lamellae are normal to the mica plane. Electric potential maps of SDS obtained by KFM show well-defined electrostatic patterns: surfactant layers deposited on mica are overall negative with a larger excess of negative charge in the interlamellar space than in the lamellar faces.
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Affiliation(s)
- Juliana S Bernardes
- Institute of Chemistry, University of Campinas, UNICAMP, P.O. Box 6154, 13084-971, Campinas-SP, Brazil
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222
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Sarkar J, Sharma A. A unified theory of instabilities in viscoelastic thin films: from wetting to confined films, from viscous to elastic films, and from short to long waves. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:8464-8473. [PMID: 20205403 DOI: 10.1021/la9049007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A general unified theory of field (van der Waals, electric, etc.)-induced surface instabilities in thin viscoelastic films that accounts for a destabilizing field and stabilizing effects of elastic strain and surface energy is presented. The present theory seamlessly covers the instability and its different regimes in films ranging from elastic to viscous, from adhesive (confined) to wetting (free surface), and from short- to long-wave instabilities. The critical conditions for the onset of instability are found to be strongly dependent on elastic properties such as the shear modulus of the film, but the dominant wavelength is strikingly independent of the film rheology. Different regimes based on a nondimensional parameter (gamma/mu h) are uncovered, where gamma is the surface energy, mu is the elastic shear modulus, and h is the film thickness. A short-wave, elasticlike response with wavelength lambda approximately = 2.96 h is obtained for gamma/mu h < 0.1, whereas long waves that depend nonlinearly on the field strength and surface energy are obtained for gamma/mu h > 1. Owing to their small critical thickness, wetting films destabilized by intermolecular forces always display long-wave instability regardless of their viscoelasticity. Furthermore, our numerical simulations based on energy minimization for unstable wetting elastic films show the formation of islands for ultrathin films and a morphological phase transition to holes embedded in the film for relatively thicker films. Unlike viscous films, however, unstable elastic films do not display a unique dominant wavelength but a bimodal distribution of wavelengths.
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Affiliation(s)
- Jayati Sarkar
- Department of Chemical Engineering, Indian Institute of Technology, Delhi 110016, India
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223
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Bäumchen O, Lessel M, Fetzer R, Seemann R, Jacobs K. Sliding fluids: Dewetting experiments reveal the solid/liquid boundary condition. ACTA ACUST UNITED AC 2010. [DOI: 10.1088/1742-6596/216/1/012002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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224
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Mezger M, Sedlmeier F, Horinek D, Reichert H, Pontoni D, Dosch H. On the Origin of the Hydrophobic Water Gap: An X-ray Reflectivity and MD Simulation Study. J Am Chem Soc 2010; 132:6735-41. [DOI: 10.1021/ja910624j] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Markus Mezger
- Max-Planck-Institut für Metallforschung, Heisenbergstr. 3, 70569 Stuttgart, Germany, Department of Chemical Engineering, University of California, Berkeley, California 94720, Physik Department, Technische Universität München, 85748 Garching, Germany, and European Synchrotron Radiation Facility, 6 rue Jules Horowitz, 38043 Grenoble, France
| | - Felix Sedlmeier
- Max-Planck-Institut für Metallforschung, Heisenbergstr. 3, 70569 Stuttgart, Germany, Department of Chemical Engineering, University of California, Berkeley, California 94720, Physik Department, Technische Universität München, 85748 Garching, Germany, and European Synchrotron Radiation Facility, 6 rue Jules Horowitz, 38043 Grenoble, France
| | - Dominik Horinek
- Max-Planck-Institut für Metallforschung, Heisenbergstr. 3, 70569 Stuttgart, Germany, Department of Chemical Engineering, University of California, Berkeley, California 94720, Physik Department, Technische Universität München, 85748 Garching, Germany, and European Synchrotron Radiation Facility, 6 rue Jules Horowitz, 38043 Grenoble, France
| | - Harald Reichert
- Max-Planck-Institut für Metallforschung, Heisenbergstr. 3, 70569 Stuttgart, Germany, Department of Chemical Engineering, University of California, Berkeley, California 94720, Physik Department, Technische Universität München, 85748 Garching, Germany, and European Synchrotron Radiation Facility, 6 rue Jules Horowitz, 38043 Grenoble, France
| | - Diego Pontoni
- Max-Planck-Institut für Metallforschung, Heisenbergstr. 3, 70569 Stuttgart, Germany, Department of Chemical Engineering, University of California, Berkeley, California 94720, Physik Department, Technische Universität München, 85748 Garching, Germany, and European Synchrotron Radiation Facility, 6 rue Jules Horowitz, 38043 Grenoble, France
| | - Helmut Dosch
- Max-Planck-Institut für Metallforschung, Heisenbergstr. 3, 70569 Stuttgart, Germany, Department of Chemical Engineering, University of California, Berkeley, California 94720, Physik Department, Technische Universität München, 85748 Garching, Germany, and European Synchrotron Radiation Facility, 6 rue Jules Horowitz, 38043 Grenoble, France
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225
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Calò A, Stoliar P, Matacotta FC, Cavallini M, Biscarini F. Time-temperature integrator based on the dewetting of polyisobutylene thin films. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:5312-5315. [PMID: 20334414 DOI: 10.1021/la1008279] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
This work reports the application of a patterned thin film of polyisobutylene (PIB) irradiated with an electron beam as a time-temperature integrator, i.e., a device that is able to record the thermal history of a product. The device is fabricated by irradiation with an electron beam of regions of a PIB thin film to different doses of electrons. A different dewetting behavior occurs at these regions upon thermal exposure, depending on the dose. The experimental results are quantified by means of a model of dewetting based on nucleation and growth of holes in a strong slippage regime.
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226
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Cornelsen M, Helm CA, Block S. Destabilization of Polyelectrolyte Multilayers Formed at Different Temperatures and Ion Concentrations. Macromolecules 2010. [DOI: 10.1021/ma9027883] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Matthias Cornelsen
- Antriebstechnik und Mechatronik, Universität Rostock, Justus-von-Liebig-Weg 6, D-18059 Rostock, Germany
| | - Christiane A. Helm
- Institut für Physik, Ernst-Moritz-Arndt Universität, Felix-Hausdorff-Str. 6, D-17489 Greifswald, Germany
| | - Stephan Block
- Institut für Physik, Ernst-Moritz-Arndt Universität, Felix-Hausdorff-Str. 6, D-17489 Greifswald, Germany
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227
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Archer AJ, Robbins MJ, Thiele U. Dynamical density functional theory for the dewetting of evaporating thin films of nanoparticle suspensions exhibiting pattern formation. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 81:021602. [PMID: 20365569 DOI: 10.1103/physreve.81.021602] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Revised: 09/16/2009] [Indexed: 05/29/2023]
Abstract
Recent experiments have shown that the striking structure formation in dewetting films of evaporating colloidal nanoparticle suspensions occurs in an ultrathin "postcursor" layer that is left behind by a mesoscopic dewetting front. Various phase change and transport processes occur in the postcursor layer that may lead to nanoparticle deposits in the form of labyrinthine, network, or strongly branched "finger" structures. We develop a versatile dynamical density functional theory to model this system which captures all these structures and may be employed to investigate the influence of evaporation or condensation, nanoparticle transport, and solute transport in a differentiated way. We highlight, in particular, the influence of the subtle interplay of decomposition in the layer and contact line motion on the observed particle-induced transverse instability of the dewetting front.
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Affiliation(s)
- A J Archer
- Department of Mathematical Sciences, Loughborough University, Leicestershire LE11 3TU, United Kingdom
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228
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Diamant H, Agam O. Localized rayleigh instability in evaporation fronts. PHYSICAL REVIEW LETTERS 2010; 104:047801. [PMID: 20366739 DOI: 10.1103/physrevlett.104.047801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2009] [Indexed: 05/29/2023]
Abstract
A qualitatively different manifestation of the Rayleigh instability is demonstrated, where, instead of the usual extended undulations and breakup of the liquid into many droplets, the instability is localized, leading to an isolated narrowing of the liquid filament. The localized instability, caused by a nonuniform curvature of the liquid domain, plays a key role in the evaporation of thin liquid films off solid surfaces.
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Affiliation(s)
- Haim Diamant
- School of Chemistry, Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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229
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Bäumchen O, Jacobs K. Slip effects in polymer thin films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:033102. [PMID: 21386275 DOI: 10.1088/0953-8984/22/3/033102] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Probing the fluid dynamics of thin films is an excellent tool for studying the solid/liquid boundary condition. There is no need for external stimulation or pumping of the liquid, due to the fact that the dewetting process, an internal mechanism, acts as a driving force for liquid flow. Viscous dissipation, within the liquid, and slippage balance interfacial forces. Thus, friction at the solid/liquid interface plays a key role towards the flow dynamics of the liquid. Probing the temporal and spatial evolution of growing holes or retracting straight fronts gives, in combination with theoretical models, information on the liquid flow field and, especially, the boundary condition at the interface. We review the basic models and experimental results obtained during the last several years with exclusive regard to polymers as ideal model liquids for fluid flow. Moreover, concepts that aim to explain slippage on the molecular scale are summarized and discussed.
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Affiliation(s)
- O Bäumchen
- Department of Experimental Physics, Saarland University, D-66041 Saarbrücken, Germany
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230
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Tang S, Vongehr S, Meng X. Controllable incorporation of Ag and Ag–Au nanoparticles in carbon spheres for tunable optical and catalytic properties. ACTA ACUST UNITED AC 2010. [DOI: 10.1039/c0jm00456a] [Citation(s) in RCA: 160] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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231
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Bäumchen O, Fetzer R, Jacobs K. Reduced interfacial entanglement density affects the boundary conditions of polymer flow. PHYSICAL REVIEW LETTERS 2009; 103:247801. [PMID: 20366229 DOI: 10.1103/physrevlett.103.247801] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2009] [Indexed: 05/29/2023]
Abstract
Hydrodynamic boundary conditions play a crucial role in the flow dynamics of thin films and can be probed by the analysis of liquid front profiles. For long-chained polymer films it was reported that a deviation from a symmetric profile is a result of viscoelastic effects. In this Letter, however, evidence is given that merely a slip-boundary condition at the solid-liquid interface can lead to an asymmetric profile. Variation of molecular weight shows that slippage is directly linked to chain entanglements. We find a reduced entanglement density at the solid-liquid interface (factors 3 to 4), which stresses the importance of considering nonbulk polymer properties in the vicinity of an interface.
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Affiliation(s)
- O Bäumchen
- Department of Experimental Physics, Saarland University, D-66041 Saarbrücken, Germany
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232
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Chen X, Anthamatten M. Solvent-assisted dewetting during chemical vapor deposition. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:11555-11562. [PMID: 19670895 DOI: 10.1021/la901481q] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
This study examines the use of a nonreactive solvent vapor, tert-butanol, during initiated chemical vapor deposition (iCVD) to promote polymer film dewetting. iCVD is a solventless technique to grow polymer thin films directly from gas phase feeds. Using a custom-built axisymmetric hot-zone reactor, smooth poly(methyl methacrylate) films are grown from methyl methacrylate (MMA) and tert-butyl peroxide (TBPO). When solvent vapor is used, nonequilibrium dewetted structures comprising of randomly distributed polymer droplets are observed. The length scale of observed topographies, determined using power spectral density (PSD) analysis, ranges from 5 to 100 microm and is influenced by deposition conditions, especially the carrier gas and solvent vapor flow rates. The use of a carrier gas leads to faster deposition rates and suppresses thin film dewetting. The use of solvent vapor promotes dewetting and leads to larger length scales of the dewetted features. Control over lateral length scale is demonstrated by preparation of hierarchal "bump on bump" topographies. Vapor-induced dewetting is demonstrated on silicon wafer substrate with a native oxide layer and also on hydrophobically modified substrate prepared using silane coupling. Autophobic dewetting of PMMA from SiOx/Si during iCVD is attributed to a thin film instability driven by both long-range van der Waals forces and short-range polar interactions.
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Affiliation(s)
- Xichong Chen
- Department of Chemical Engineering, University of Rochester, Rochester, New York 14627, USA
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233
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Panagiotou P, Bauer E, Loi S, Titz T, Maurer E, Müller-Buschbaum P. Polymeric structures at interfaces: An X-ray scattering study. Z KRIST-CRYST MATER 2009. [DOI: 10.1524/zkri.219.4.210.30444] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
X-ray scattering based on synchrotron radiation enables the detection of polymeric structures at interfaces despite the weak contrast between adjacent polymers build-up from different monomeric units. Variable types of polymeric structures result from typical pattern directing mechanisms, such as dewetting in case of homopolymer films, phase separation in polymer blend films, micro-phase separation in diblock copolymer films and surface enrichment in statistical copolymer films. The pattern directing mechanisms introduce structures ordered perpendicular and parallel to the polymeric surface. Consequently, specular and off-specular X-ray scattering is applied as demonstrated within examples. From scattering the characteristic structures which are not accessible by means of other techniques are determined. Limitations with respect to isolated objects such as holes are discussed.
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234
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Rezende CA, Lee LT, Galembeck F. Surface mechanical properties of thin polymer films investigated by AFM in pulsed force mode. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:9938-9946. [PMID: 19705889 DOI: 10.1021/la9010949] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Atomic force microscopy in the pulsed force mode (PFM) is applied in this work to the study of thin dewetting patterns formed by drying an aqueous solution of poly(N-isopropylacrylamide) (PNIPAM) and sodium dodecyl sulfate (SDS) on mica. This technique allows the automated acquisition of typically 4 x 10(6) force-distance curves on the sample surface together with maps showing nanodomains differentiated by their stiffness and adhesion to the tip. Topography images of dry films revealed a morphology formed by droplets distributed on the substrate. Adhesion and stiffness images with good lateral resolution show droplets containing polymer and surfactant contrasting with the substrate and also nanosized heterogeneities inside these droplets. They also revealed very small dewetted structures which could not be observed in the topography map by noncontact AFM. Adhesion interactions between the AFM tip and the polymer or the dewetted mica substrate were measured in terms of adhesion force and detachment energy, and can be used as new information to understand dewetting patterns containing silica particles, PNIPAM, and SDS. Other surface mechanical parameters such as stiffness, maximum indentation, hardness, compliance, hysteresis, and Young's modulus were obtained by sampling many points and used to characterize the PNIPAM/SDS films formed in the dewetting process.
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Affiliation(s)
- Camila A Rezende
- Institute of Chemistry, University of Campinas - UNICAMP, P.O. Box 6154, CEP 13083-970, Campinas - SP, Brazil
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235
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You J, Hu S, Liao Y, Song K, Men Y, Shi T, An L. Composition effect on dewetting of ultrathin films of miscible polymer blend. POLYMER 2009. [DOI: 10.1016/j.polymer.2009.08.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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236
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Thiele U, Vancea I, Archer AJ, Robbins MJ, Frastia L, Stannard A, Pauliac-Vaujour E, Martin CP, Blunt MO, Moriarty PJ. Modelling approaches to the dewetting of evaporating thin films of nanoparticle suspensions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:264016. [PMID: 21828464 DOI: 10.1088/0953-8984/21/26/264016] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We review recent experiments on dewetting thin films of evaporating colloidal nanoparticle suspensions (nanofluids) and discuss several theoretical approaches to describe the ongoing processes including coupled transport and phase changes. These approaches range from microscopic discrete stochastic theories to mesoscopic continuous deterministic descriptions. In particular, we describe (i) a microscopic kinetic Monte Carlo model, (ii) a dynamical density functional theory and (iii) a hydrodynamic thin film model. Models (i) and (ii) are employed to discuss the formation of polygonal networks, spinodal and branched structures resulting from the dewetting of an ultrathin 'postcursor film' that remains behind a mesoscopic dewetting front. We highlight, in particular, the presence of a transverse instability in the evaporative dewetting front, which results in highly branched fingering structures. The subtle interplay of decomposition in the film and contact line motion is discussed. Finally, we discuss a simple thin film model (iii) of the hydrodynamics on the mesoscale. We employ coupled evolution equations for the film thickness profile and mean particle concentration. The model is used to discuss the self-pinning and depinning of a contact line related to the 'coffee-stain' effect. In the course of the review we discuss the advantages and limitations of the different theories, as well as possible future developments and extensions.
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Affiliation(s)
- U Thiele
- Department of Mathematical Sciences, Loughborough University, Leicestershire LE11 3TU, UK
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237
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Han ZJ, Tay BK. Dewetting of polymer films by ion implantation. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2009; 28:273-278. [PMID: 19169883 DOI: 10.1140/epje/i2008-10430-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Accepted: 12/11/2008] [Indexed: 05/27/2023]
Abstract
We report dewetting of thermodynamically stable, thick (approximately 100 nm) polystyrene films by titanium ion implantation. The dynamic dewetting patterns in time evolution are recorded. The dewetting mechanism is determined to be heterogeneous nucleation, where the defects and Ti nanoparticles formed by ion implantation serve as the nuclei. In addition, we observe abundant rims with regular polygonal shapes in dewetting patterns. This is attributed to fingering instability, which results from the balance between the driving force arisen from thermally induced surface tension gradient and the resistive forces from the combination of friction force, Laplace pressure and long-range van der Waals interactions. Finally, a model based on mass conservation is used to qualitatively describe the transition from circular to polygonal shaped rims at a critical diameter for holes.
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Affiliation(s)
- Z J Han
- Nanoelectronics Lab I, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore.
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238
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239
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Bureau L, Arvengas A. Drainage of a nanoconfined simple fluid: rate effects on squeeze-out dynamics. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 78:061501. [PMID: 19256840 DOI: 10.1103/physreve.78.061501] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2008] [Indexed: 05/27/2023]
Abstract
We investigate the effect of loading rate on drainage in molecularly thin films of a simple fluid made of quasispherical molecules [octamethylcyclotetrasiloxane (OMCTS)]. We find that (i) rapidly confined OMCTS retains its tendency to organize into layers parallel to the confining surfaces, and (ii) flow resistance in such layered films can be described by bulklike viscous forces if one accounts for the existence of one monolayer immobilized on each surface. The latter result is fully consistent with the recent work of Becker and Mugele, who reached a similar conclusion by analyzing the dynamics of squeeze-out fronts in OMCTS [T. Becker and F. Mugele, Phys. Rev. Lett. 91, 166104 (2003)]. Furthermore, we show that the confinement rate controls the nature of the thinning transitions: layer-by-layer expulsion of molecules in metastable, slowly confined films proceeds by a nucleation-growth mechanism, whereas deeply and rapidly quenched films are unstable and undergo thinning transitions akin to spinodal decomposition.
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Affiliation(s)
- Lionel Bureau
- Institut des Nanosciences de Paris, UMR 7588 CNRS-Universités Paris 6 and 7, 140 Rue de Lourmel, 75015 Paris, France.
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240
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Rauscher M, Blossey R, Münch A, Wagner B. Spinodal dewetting of thin films with large interfacial slip: implications from the dispersion relation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:12290-12294. [PMID: 18844382 DOI: 10.1021/la802260b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We compare the dispersion relations for spinodally dewetting thin liquid films for increasing magnitude of interfacial slip length in the lubrication limit. While the shape of the dispersion relation, in particular the position of the maximum, are equal for no-slip up to moderate-slip lengths, the position of the maximum shifts to much larger wavelengths for large slip lengths. Here, we discuss the implications of this fact for recently developed methods to assess the disjoining pressure in spinodally unstable thin films by measuring the shape of the roughness power spectrum. For polystyrene (PS) films on octadecyltrichlorosilane (OTS) covered Si wafers (with slip length b approximately 1 microm), we predict a 20% shift of the position of the maximum of the power spectrum which should be detectable in experiments.
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Affiliation(s)
- Markus Rauscher
- Max-Planck-Institut for Metallforschung, Heisenbergstrasse 3, 70569 Stuttgart, Germany.
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241
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Calò A, Stoliar P, Cavallini M, Sergeyev S, Geerts YH, Biscarini F. Monolayer Control of Discotic Liquid Crystal by Electromigration of Dewetted Layers in Thin Film Devices. J Am Chem Soc 2008; 130:11953-8. [DOI: 10.1021/ja801337v] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Annalisa Calò
- CNR−Institute for the Study of Nanostructured Materials, Via Gobetti 101, 40129 Bologna, Italy, and Laboratory of Polymer Chemistry CP 206/1, Université Libre de Bruxelles, Boulevard du Triomphe, 1050 Bruxelles, Belgium
| | - Pablo Stoliar
- CNR−Institute for the Study of Nanostructured Materials, Via Gobetti 101, 40129 Bologna, Italy, and Laboratory of Polymer Chemistry CP 206/1, Université Libre de Bruxelles, Boulevard du Triomphe, 1050 Bruxelles, Belgium
| | - Massimiliano Cavallini
- CNR−Institute for the Study of Nanostructured Materials, Via Gobetti 101, 40129 Bologna, Italy, and Laboratory of Polymer Chemistry CP 206/1, Université Libre de Bruxelles, Boulevard du Triomphe, 1050 Bruxelles, Belgium
| | - Sergey Sergeyev
- CNR−Institute for the Study of Nanostructured Materials, Via Gobetti 101, 40129 Bologna, Italy, and Laboratory of Polymer Chemistry CP 206/1, Université Libre de Bruxelles, Boulevard du Triomphe, 1050 Bruxelles, Belgium
| | - Yves H. Geerts
- CNR−Institute for the Study of Nanostructured Materials, Via Gobetti 101, 40129 Bologna, Italy, and Laboratory of Polymer Chemistry CP 206/1, Université Libre de Bruxelles, Boulevard du Triomphe, 1050 Bruxelles, Belgium
| | - Fabio Biscarini
- CNR−Institute for the Study of Nanostructured Materials, Via Gobetti 101, 40129 Bologna, Italy, and Laboratory of Polymer Chemistry CP 206/1, Université Libre de Bruxelles, Boulevard du Triomphe, 1050 Bruxelles, Belgium
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242
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Xue L, Cheng Z, Fu J, Han Y. Dewetting behavior of polystyrene film filled with (C6H5C2H4NH3)2PbI4. J Chem Phys 2008; 129:054905. [DOI: 10.1063/1.2957899] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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243
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Moosavi A, Rauscher M, Dietrich S. Size dependent motion of nanodroplets on chemical steps. J Chem Phys 2008; 129:044706. [DOI: 10.1063/1.2955860] [Citation(s) in RCA: 16] [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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244
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McGarrity ES, Duxbury PM, Mackay ME, Frischknecht AL. Calculation of Entropic Terms Governing Nanoparticle Self-Assembly in Polymer Films. Macromolecules 2008. [DOI: 10.1021/ma801003e] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Erin S. McGarrity
- Department of Chemical Engineering & Materials Science, Michigan State University, East Lansing, Michigan 48824-1226; Department of Physics & Astronomy, Michigan State University, East Lansing, Michigan 48824-1226; and Sandia National Laboratories, Albuquerque, New Mexico 87185
| | - Phillip M. Duxbury
- Department of Chemical Engineering & Materials Science, Michigan State University, East Lansing, Michigan 48824-1226; Department of Physics & Astronomy, Michigan State University, East Lansing, Michigan 48824-1226; and Sandia National Laboratories, Albuquerque, New Mexico 87185
| | - Michael E. Mackay
- Department of Chemical Engineering & Materials Science, Michigan State University, East Lansing, Michigan 48824-1226; Department of Physics & Astronomy, Michigan State University, East Lansing, Michigan 48824-1226; and Sandia National Laboratories, Albuquerque, New Mexico 87185
| | - Amalie L. Frischknecht
- Department of Chemical Engineering & Materials Science, Michigan State University, East Lansing, Michigan 48824-1226; Department of Physics & Astronomy, Michigan State University, East Lansing, Michigan 48824-1226; and Sandia National Laboratories, Albuquerque, New Mexico 87185
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245
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Trice J, Favazza C, Thomas D, Garcia H, Kalyanaraman R, Sureshkumar R. Novel self-organization mechanism in ultrathin liquid films: theory and experiment. PHYSICAL REVIEW LETTERS 2008; 101:017802. [PMID: 18764153 DOI: 10.1103/physrevlett.101.017802] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2008] [Indexed: 05/26/2023]
Abstract
When an ultrathin metal film of thickness h (<20 nm) is melted by a nanosecond pulsed laser, the film temperature is a nonmonotonic function of h and achieves its maximum at a certain thickness h*. This is a consequence of the h and time dependence of energy absorption and heat flow. Linear stability analysis and nonlinear dynamical simulations that incorporate such intrinsic interfacial thermal gradients predict a characteristic pattern length scale Lambda that decreases for h>h*, in contrast to the classical spinodal dewetting behavior where Lambda increases monotonically as h2. These predictions agree well with experimental observations for Co and Fe films on SiO2.
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Affiliation(s)
- Justin Trice
- Department of Physics, Washington University, St. Louis, Missouri 63130, USA
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246
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Kojima Y, Kato T. Nanoparticle formation in Au thin films by electron-beam-induced dewetting. NANOTECHNOLOGY 2008; 19:255605. [PMID: 21828657 DOI: 10.1088/0957-4484/19/25/255605] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
We carried out investigations on electron-beam-induced nanoparticle formation in thin (5-30 nm) Au films on smooth SiO(2)/Si substrates. When the Au films were irradiated with an electron beam, the Au films broke up into nanoparticles through the dewetting process. The dominant wavelengths of the surface (corresponding to the pitch between nanoparticles) were closely related with the thickness of the Au. We then developed a new technique for the formation of periodically arranged Au nanoparticles using a holed substrate. The nanoholes induced heterogeneous nucleation and helped to form ordered nanoparticles between the holes. Two-dimensionally, periodically arranged Au nanoparticles with a pitch of 100 nm were obtained.
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Affiliation(s)
- Yasuhiko Kojima
- Engineering Section, Elionix Inc., 3-7-6 Motoyokoyama, Hachiouji, Tokyo 192-0063, Japan
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247
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Chraïbi H, Lasseux D, Arquis E, Wunenburger R, Delville JP. Stretching and squeezing of sessile dielectric drops by the optical radiation pressure. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 77:066706. [PMID: 18643396 DOI: 10.1103/physreve.77.066706] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Indexed: 05/26/2023]
Abstract
We study numerically the deformation of sessile dielectric drops immersed in a second fluid when submitted to the optical radiation pressure of a continuous Gaussian laser wave. Both drop stretching and drop squeezing are investigated at steady state where capillary effects balance the optical radiation pressure. A boundary integral method is implemented to solve the axisymmetric Stokes flow in the two fluids. In the stretching case, we find that the drop shape goes from prolate to near-conical for increasing optical radiation pressure whatever the drop to beam radius ratio and the refractive index contrast between the two fluids. The semiangle of the cone at equilibrium decreases with the drop to beam radius ratio and is weakly influenced by the index contrast. Above a threshold value of the radiation pressure, these "optical cones" become unstable and a disruption is observed. Conversely, when optically squeezed, the drop shifts from an oblate to a concave shape leading to the formation of a stable "optical torus." These findings extend the electrohydrodynamics approach of drop deformation to the much less investigated "optical domain" and reveal the openings offered by laser waves to actively manipulate droplets at the micrometer scale.
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Affiliation(s)
- Hamza Chraïbi
- Transferts, Ecoulements, Fluides, Energétique (UMR CNRS 8508), Université Bordeaux I, Esplanade des Arts et Métiers, 33405 Talence Cedex, France
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248
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Cai Y, Newby BMZ. Dewetting of polystyrene thin films on poly(ethylene glycol)-modified surfaces as a simple approach for patterning proteins. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:5202-5208. [PMID: 18407678 DOI: 10.1021/la703923z] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
A simple technique for patterning proteins utilizing dewetted polystyrene (PS) droplets is demonstrated. A polystyrene thin film was spin coated on a poly(ethylene glycol) (PEG) silane-modified surface. As the PS film dewets from the surface, upon annealing, to form droplets, the PEG-silane-modified surface is exposed, which retains its capability to resist protein adsorption, and the PS droplets allow the selective adsorption of proteins. In contrast to the undewetted flat PS film, the droplet surface had a greater amount of adsorbed proteins. Atomic force microscopy scans reveal that the roughness of the droplet surface is higher, and a multilayer of proteins results on the droplet surface. Moreover, micro- and nanoscale droplet patterns can easily be achieved by tuning the thickness of PS thin films. Because dewetting approaches for generating ordered dewetting droplets have been successfully generated by others, those approaches could be easily combined with this technique to fabricate ordered protein patterns.
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Affiliation(s)
- Yangjun Cai
- Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, OH 44325-3906, USA
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249
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Al Akhrass S, Reiter G, Hou SY, Yang MH, Chang YL, Chang FC, Wang CF, Yang ACM. Viscoelastic thin polymer films under transient residual stresses: two-stage dewetting on soft substrates. PHYSICAL REVIEW LETTERS 2008; 100:178301. [PMID: 18518343 DOI: 10.1103/physrevlett.100.178301] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2007] [Indexed: 05/26/2023]
Abstract
A nonmonotonic, two-stage dewetting behavior was observed for spin coated thin viscoelastic polymer films on soft elastic substrates. At times shorter than the relaxation time of the polymer (t<tau_{rep}), dewetting generated deep trenches in the soft rubbery substrate which, in turn, almost stopped dewetting. At later stages (t>>tau_{rep}), dewetting accelerated, accompanied by an unstable rim. However, holes nucleated at t<tau_{rep} showed only this second-stage behavior. Our observations are attributed to large elastic deformations in the substrate caused by transient residual stresses within the film.
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Affiliation(s)
- S Al Akhrass
- Institute de Chimie des Surfaces et Interfaces, UHA-CNRS, 15, rue J. Starcky, 68057 Mulhouse Cedex, France
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250
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Fukuzawa K, Deguchi T, Yamawaki Y, Itoh S, Muramatsu T, Zhang H. Control of wettability of molecularly thin liquid films by nanostructures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:2921-2928. [PMID: 18237215 DOI: 10.1021/la703106s] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The patterning of liquid thin films on solid surfaces is very important in various fields of science and engineering related to surfaces and interfaces. A method of nanometer-scale patterning of a molecularly thin liquid film on a silicon substrate using the lyophobicity of the oxide nanostructures has recently been reported (Fukuzawa, K.; Deguchi, T.; Kawamura, J.; Mitsuya, Y.; Muramatsu, T.; Zhang, H. Appl. Phys. Lett. 2005, 87, 203108). However, the origin of the lyophobicity of the nanostructure with a height of around 1 nm, which was fabricated by probe oxidation, has not yet been clarified. In the present study, the change in thickness of the liquid film on mesa-shaped nanostructures and the wettability for the various combinations of the thickness of the liquid films and the height of ridge-shaped nanostructures were investigated. These revealed that lyophobicity is caused by a lowering of the intermolecular interaction between the liquid and silicon surfaces by the nanostructure and enables the patterning of a liquid film along it. The tendency of the wettability for a given liquid film and nanostructure size can be predicted by estimating the contributions of the intermolecular interaction and capillary pressure. In this method, the height of the nanostructure can control the wettability. These results can provide a novel method of nanoscale patterning of liquid thin films, which will be very useful in creating new functional surfaces.
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Affiliation(s)
- Kenji Fukuzawa
- Department of Micro/Nano Systems Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan.
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