Pattern formation in unstable thin liquid films under the influence of antagonistic short- and long-range forces

Sharma, Ashutosh; Khanna, Rajesh

doi:10.1063/1.478378

Cited by 125 publications

(145 citation statements)

References 36 publications

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“…Though both mechanisms have been detected, 39 the first is the most studied one. Its evolution has been modeled with London-van der Waals attraction and double-layer repulsion by Vrij, 40 the London-van der Waals force by Williams and Davis, 41 short-and long-range forces by Sharma et al, 34,42,43 and the effects of drying by Schwartz et al 35 For pure liquids it is believed that film rupture is due to competition of long-͑apolar, van der Waals͒ and short-range polar forces, resulting in an intermolecular interaction free energy of the form ⌬F =−A /12 h 2 + S exp͑−h / l͒. In general, the stability characteristics depend upon the orientation of double layers at both interfaces, which in turn are influenced by the type of solvent and surfactant molecules.…”

Section: B Measurability Region and Film Stabilitymentioning

confidence: 99%

Experimental study of substrate roughness and surfactant effects on the Landau-Levich law

Krechetnikov

Homsy

2005

Physics of Fluids

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In this work we present an experimental study of deviations from the classical Landau-Levich law in the problem of dip coating. Among the examined causes leading to deviations are the nature of the liquid-gas and liquid-solid interfaces. The thickness of the coating film created by withdrawal of a plate from a bath was measured gravimetrically over a wide range of capillary numbers for both smooth and well-characterized rough substrates, and for clean and surfactant interface cases. In view of the dependence of the lifetime of a film on the type of liquid and substrate, and liquid-gas and liquid-solid interfaces, we characterized the range of measurability of the film thickness in the parameter space defined by the withdrawal capillary number, the surfactant concentration, and substrate roughness size. We then study experimentally the effect of a film thickening due to the presence of surfactants. Our recent theory based on a purely hydrodynamic role of the surface active substance suggests that there is a sorption-controlled coating regime in which Marangoni effects should lead to film thinning. However, our experiments conducted in this regime demonstrate film thickening, calling into question the conventional wisdom, which is that Marangoni stresses ͑as accounted by the conventional interfacial boundary conditions͒ lead to film thickening. Next we examine the effect of well-characterized substrate roughness on the coated film thickness, which also reveals its influence on wetting-related processes and an effective boundary condition at the wall. In particular, it is found that roughness results in a significant thickening of the film relative to that on a smooth substrate and a different power of capillary number than the classical Landau-Levich law.

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Section: B Measurability Region and Film Stabilitymentioning

confidence: 99%

Experimental study of substrate roughness and surfactant effects on the Landau-Levich law

Krechetnikov

Homsy

2005

Physics of Fluids

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“…Both can be destabilizing or stabilizing. Their combination gives four types of disjoining pressures [31,32] that have been used to study the twoand three-dimensional evolution of unstable films [33][34][35][36]. Including a thin coating layer on the substrate extends the number of terms and, therefore, the possible variations [8,16,37].…”

Section: Introductionmentioning

confidence: 99%

On the importance of nucleation solutions for the rupture of thin liquid films

Thiele

Neuffer

Pomeau

et al. 2002

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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The process of dewetting of a thin liquid film is usually described using a long wave approximation yielding a single evolution equation for the film thickness. This equation incorporates an additional pressure term-the disjoining pressure-accounting for the effective interaction of the thin film with the substrate. We use the equation to study the evolution of unstable thin films examining the thickness ranges for linear instability and metastability for flat films, the families of stationary periodic and localized solutions and their linear stability. From this we conclude that within the linearly unstable thickness range exists a well defined subrange where finite perturbations are crucial for the time evolution and the resulting structures. In the remainder of the linearly unstable thickness range the resulting structures are controlled by the fastest flat film mode as was assumed up to now for all the linearly unstable thickness range. The results are shown for a disjoining pressure derived by coupling hydrodynamics to the diffuse interface model and for disjoining pressures combining destabilizing [stabilizing] polar short-range interaction with stabilizing [destabilizing] apolar long-range interaction. Finally, the implications for spinodal decomposition of a binary mixture are discussed.

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“…The competition of attractive van der Waals forces and short range repulsive forces, like Born repulsion, can produce complex instabilities in layers of thin liquid films on solid substrates. Experimental studies have shown this behavior for polymer films [66,81,87,88,101], liquid crystal films [58,93,94], liquid metals [29,58] and evaporating films [41,76]. During these dewetting processes, large droplets are formed which are connected by ultra-thin films.…”

Section: Dewetting Filmsmentioning

confidence: 99%

“…As described above, the turning points separate families of stable and unstable solutions on this branch. The unstable solutions have a finite amplitude structure, with h min = O(1) as ǫ → 0, while the stable solutions are localized droplets connected by an ultra-thin film with thickness h ∼ ǫ (see Figure 10) and approach the homoclinic solution of (88). These stable droplet solutions concentrate mass as a δ-distribution in the limit of vanishing ǫ.…”

Section: Asymptotic Behavior Of Equilibrium Solutionsmentioning

confidence: 99%

“…In addition, for 0 ≤p < P max , (88) has a hyperbolic saddle point at h s ∼ ǫ + ǫ n+1p /(m − n) as ǫ → 0 with h c > h s . The stable and unstable manifolds of the saddle point form a homoclinic orbit that encloses h c and all of the periodic solutions of (88). Periodic solutions surrounding the center h c have a minimum greater than the saddle point value h s .…”

Section: One-dimensional Steady-state Solutionsmentioning

confidence: 99%

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Thin film dynamics: theory and applications

Bertozzi

Bowen

2002

Modern Methods in Scientific Computing and Applications

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This paper is based on a series of four lectures, by the first author, on thin films and moving contact lines. Section one presents an overview of the moving contact line problem and introduces the lubrication approximation. Section two summarizes results for positivity preserving schemes. Section three discusses the problem of films driven by thermal gradients with an opposing gravitational force. Such systems yield complex dynamics featuring undercompressive shocks. We conclude in section four with a discussion of of dewetting films.

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Pattern formation in unstable thin liquid films under the influence of antagonistic short- and long-range forces

Abstract: The effect of electric fields on the rupture of thin viscous films by van der Waals forces Phys. Fluids 15, 641 (2003); 10.1063/1.1538250Self-organized structures in thin liquid films on chemically heterogeneous substrates: Effect of antagonistic short and long range interactions

Cited by 125 publications

References 36 publications

Experimental study of substrate roughness and surfactant effects on the Landau-Levich law

Experimental study of substrate roughness and surfactant effects on the Landau-Levich law

On the importance of nucleation solutions for the rupture of thin liquid films

Thin film dynamics: theory and applications

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