Late stage spreading of stratified liquids: Theory

Ausserré, Dominique; Buraud, Jean-Luc

doi:10.1063/1.3556670

Cited by 4 publications

(18 citation statements)

References 17 publications

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“…The remaining parameters to be determined are: γ, the surface tension; K, the bulk elastic constant; θ F , free surface azimuthal anchoring angle; θ S , substrate azimuthal anchoring angle; Â, a force per unit volume, proportional to the Hamaker constant; and μ, a representative viscosity. Many experimental studies, such as Ausserré & Buraud (2011); Cazabat et al (2011); van Effenterre & Valignat (2003); Poulard & Cazabat (2005); Schulz & Bahr (2011);Vandenbrouck et al (1999) use the cyanobiphenyl (nCB) series of liquid crystals (where n refers to the number of carbons in the aliphatic tail), in particular, 4-Cyano-4'-pentylbiphenyl (5CB). Therefore, we choose these physical parameters to match 5CB data.…”

Section: Scalings and Physical Parametersmentioning

confidence: 99%

Stability of thin fluid films characterised by a complex form of effective disjoining pressure

2018

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We discuss instabilities of fluid films of nanoscale thickness, with a particular focus on films where the destabilising mechanism allows for linear instability, metastability, and absolute stability. Our study is motivated by nematic liquid crystal films; however we note that similar instability mechanisms, and forms of the effective disjoining pressure, appear in other contexts, such as the well-studied problem of polymeric films on twolayered substrates. The analysis is carried out within the framework of the long-wave approximation, which leads to a fourth order nonlinear partial different equation for the film thickness. Within the considered formulation, the nematic character of the film leads to an additional contribution to the disjoining pressure, changing its functional form. This effective disjoining pressure is characterised by the presence of a local maximum for nonvanishing film thickness. Such a form leads to complicated instability evolution that we study by analytical means, including application of marginal stability criteria, and by extensive numerical simulations that help us develop a better understanding of instability evolution in the nonlinear regime. This combination of analytical and computational techniques allows us to reach novel understanding of relevant instability mechanisms, and of their influence on transient and fully developed fluid film morphologies. arXiv:1704.03919v1 [cond-mat.soft]

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Section: Scalings and Physical Parametersmentioning

confidence: 99%

Stability of thin fluid films characterised by a complex form of effective disjoining pressure

2018

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“…The mechanism of bottom layer feeding from the upper bilayers has been reported by Mohamad et al, 25 showing that lipids are transported to the bottom layer through dislocation places when humidity is increased up to the point at which the membrane transits into the fluid phase. 71 As more lipids arrive through the meniscus the concentration at the meniscus/substrate interface increases while the surface spreads outwards (thereby reducing the concentration again). It resembles the spreading of a strongly stratified smectic liquid.…”

Section: Step Iii: Surface Spreadingmentioning

confidence: 99%

“…It resembles the spreading of a strongly stratified smectic liquid. 71 As more lipids arrive through the meniscus the concentration at the meniscus/substrate interface increases while the surface spreads outwards (thereby reducing the concentration again). Eventually, the net flow at the meniscus/substrate interface gets into a dynamic equilibrium, and surface spreading follows a steady-state like kinetics.…”

Section: Step Iii: Surface Spreadingmentioning

confidence: 99%

A diffusive ink transport model for lipid dip-pen nanolithography

Urtizberea

Hirtz

2015

Nanoscale

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Despite diverse applications, phospholipid membrane stacks generated by dip-pen nanolithography (DPN) still lack a thorough and systematic characterization that elucidates the whole ink transport process from writing to surface spreading, with the aim of better controlling the resulting feature size and resolution. We report a quantitative analysis and modeling of the dependence of lipid DPN features (area, height and volume) on dwell time and relative humidity. The ink flow rate increases with humidity in agreement with meniscus size growth, determining the overall feature size. The observed time dependence indicates the existence of a balance between surface spreading and the ink flow rate that promotes differences in concentration at the meniscus/substrate interface. Feature shape is controlled by the substrate surface energy. The results are analyzed within a modified model for the ink transport of diffusive inks. At any humidity the dependence of the area spread on the dwell time shows two diffusion regimes: at short dwell times growth is controlled by meniscus diffusion while at long dwell times surface diffusion governs the process. The critical point for the switch of regime depends on the humidity.

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“…13,15 This monolayer may be the upper one, as in Figure 1a, or the lower one, as in Figure 1b. 17 The bilayer is characterized by the presence of a dislocation line at its edge. However, the height at which this dislocation is located and therefore the exact internal structure of the trilayer is unknown.…”

Section: ■ Introductionmentioning

confidence: 99%

From Permeation to Pore Nucleation in Smectic Stacks

2013

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The last stage of the spreading of a stratified droplet in the odd wetting case is the evolution from a trilayer to a monolayer, that is, vanishing of the last bilayer in the stack. We studied it in the case of 8CB smectic liquid crystal on a hydrophilic surface. Receding of the last bilayer is accompanied by formation of pores in it, which appear in the outer part of it. From analysis of real-time experimental observations of this phenomenon, we demonstrate that the dislocation loops which border these pores are not located at the same height in the trilayer stack as the dislocation lines that border the bilayer. Also, careful analysis of our results using a recently developed theoretical approach of smectic liquid nanodrop spreading strongly suggests that pore nucleation is triggered by differences in chemical potential between adjacent layers, which contrasts with the classical scheme where it is attributed to lateral tension along the layers.

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Late stage spreading of stratified liquids: Theory

Cited by 4 publications

References 17 publications

Stability of thin fluid films characterised by a complex form of effective disjoining pressure

Stability of thin fluid films characterised by a complex form of effective disjoining pressure

A diffusive ink transport model for lipid dip-pen nanolithography

From Permeation to Pore Nucleation in Smectic Stacks

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