Rayleigh instability at small length scales

Gopan, Nandu; Sathian, Sarith P.

doi:10.1103/physreve.90.033001

Cited by 18 publications

(11 citation statements)

References 22 publications

(33 reference statements)

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“…Notably, when surface tension is stronger, the breakup is faster than the analytical prediction, which suggests that the destabilising effect of surface tension can also contribute to the thread dynamics near to rupture. This limit of applicability might also explain the deviation between Eggers' similarity solution and MD results in previous studies [49,50].…”

Section: B Rupture Dynamicsmentioning

confidence: 83%

Dynamics of liquid nanothreads: Fluctuation-driven instability and rupture

2020

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The instability and rupture of nanoscale liquid threads is shown to strongly depend on thermal fluctuations. These fluctuations are naturally occurring within molecular dynamics (MD) simulations and can be incorporated via fluctuating hydrodynamics into a stochastic lubrication equation (SLE). A simple and robust numerical scheme is developed for the SLE that is validated against MD for both the initial (linear) instability and the nonlinear rupture process. Particular attention is paid to the rupture process and its statistics, where the "double-cone" profile reported by Moseler and Landmann [Science 289, 1165 (2000)] is observed, as well as other distinct profile forms depending on the flow conditions. Comparison to the Eggers' similarity solution [Phys. Rev. Lett. 89, 084502 (2002)], a power law of the minimum thread radius against time to rupture, shows agreement only at low surface tension; indicating that surface tension cannot generally be neglected when considering rupture dynamics.

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Section: B Rupture Dynamicsmentioning

confidence: 83%

Dynamics of liquid nanothreads: Fluctuation-driven instability and rupture

2020

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“…Coalescence of the resulting beads into a single large droplet is hindered by the absence of direct contact between the droplets. The distance between the droplets in the PR instability is controlled by the kinetics of the breakup and by the radius R of the initial cylindrical thread (34,35). wavelength λ ≈ 11R (39) that sets the period of the resulting array (40).…”

Section: Discussionmentioning

confidence: 99%

Periodic assembly of nanoparticle arrays in disclinations of cholesteric liquid crystals

Prince

Cho

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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An important goal of the modern soft matter science is to discover new self-assembly modalities to precisely control the placement of small particles in space. Spatial inhomogeneity of liquid crystals offers the capability to organize colloids in certain regions such as the cores of the topological defects. Here we report two selfassembly modes of nanoparticles in linear defects-disclinations in a lyotropic colloidal cholesteric liquid crystal: a continuous helicoidal thread and a periodic array of discrete beads. The beads form one-dimensional arrays with a periodicity that matches half a pitch of the cholesteric phase. The periodic assembly is governed by the anisotropic surface tension and elasticity at the interface of beads with the liquid crystal. This mode of self-assembly of nanoparticles in disclinations expands our ability to use topological defects in liquid crystals as templates for the organization of nanocolloids. colloidal liquid crystals | nanoparticle self-assembly | liquid crystal droplets | topological defects | anisotropic surface tension T he most extensively studied liquid crystalline phase, the socalled nematic, has been so named after the linear defectdisclinations that appear as flexible threads in optical microscopy textures; "thread" is "ν«μα" in Greek (1, 2). The disclinations represent singularities of the director that describes the local orientation of molecules. As one approaches the "core" of the defect, director deformation becomes so strong that the degree of orientational order varies in space. Disclinations can attract additives, e.g., colloidal particles (3-8) and even small molecules (9, 10). Such an attraction is energetically favored, as the strongly distorted disclination core region is replaced with the additive (4). The unique templating ability of disclinations has stimulated the exploration of their applications, such as the fabrication of optical materials (11), conductive microwires (12), soft magnets (13), and electrooptical devices (5,14,15).Disclinations in nematic liquid crystals are generally onedimensional structures, as the director pattern repeats itself along the line. When an additive is attracted to the disclination core, two possible morphologies are expected: (i) continuous thread-like assembly, or (ii) a linear array of discrete beads. The disclination-templated assemblies reported so far had a threadlike shape, as observed for polymers in the so-called blue phases (15) and for molecular amphiphiles at the cores of nematic disclinations (9, 10).Here, we report the templating behavior of disclinations in the chiral version of the nematic liquid crystal, the so-called cholesteric (Ch) phase. The local directorn in this phase undergoes helicoid twisting around a helical axisv while being perpendicular to this axis (1, 2). Continuous twist leads to a pseudolayered structure, with a well-defined pitch but no modulation of density. Experiments were performed for spherical Ch droplets, in which disclinations correspond to the equilibrium state, thus ensuring...

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“…For liquid flows, molecular dynamics (MD) allows one to perform nanoscale 'experiments' and these have been shown to qualitatively reproduce RP-like instability (Koplik & Banavar 1993). However, MD studies of long cylinders (Kawano 1998;Gopan & Sathian 2014) have been unable to conclusively (i.e. quantitatively) validate classical theory.…”

Section: Introductionmentioning

confidence: 99%

Revisiting the Rayleigh–Plateau instability for the nanoscale

2019

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The theoretical framework developed by Rayleigh and Plateau in the 19th century has been remarkably accurate in describing macroscale experiments of liquid cylinder instability. Here we re-evaluate and revise the Rayleigh–Plateau instability for the nanoscale, where molecular dynamics experiments demonstrate its inadequacy. A new framework based on the stochastic lubrication equation is developed that captures nanoscale flow features and highlights the critical role of thermal fluctuations at small scales. Remarkably, the model indicates that classically stable (i.e. ‘fat’) liquid cylinders can be broken at the nanoscale, and this is confirmed by molecular dynamics.

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Rayleigh instability at small length scales

Cited by 18 publications

References 22 publications

Dynamics of liquid nanothreads: Fluctuation-driven instability and rupture

Dynamics of liquid nanothreads: Fluctuation-driven instability and rupture

Periodic assembly of nanoparticle arrays in disclinations of cholesteric liquid crystals

Revisiting the Rayleigh–Plateau instability for the nanoscale

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