Crossover between 2D and 3D Fluid Dynamics in the Diffusion of Islands in Ultrathin Freely Suspended Smectic Films

Nguyen, Zoom; Atkinson, Markus; Park, Cheol Soo; Maclennan, Joseph E.; Glaser, Matthew A.; Clark, Noel A.

doi:10.1103/physrevlett.105.268304

Cited by 52 publications

(54 citation statements)

References 21 publications

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“…Since S is about two orders of magnitude smaller than the film radius in these experiments, contributions to the island mobility from confinement should be negligible. The observations are consistent with an extensive earlier study of the Brownian diffusion of islands in ultra-thin 8CB films, which showed that the islands have mobilities that follow SD/HPW theory over a wide range of ε [7]. Although they have fluid interiors, circulatory flow inside the islands induced by their motion through the background film is expected to be strongly suppressed, so that they behave hydrodynamically like solid discs.…”

supporting

confidence: 90%

“…Most rheological investigations of membranes have been made by observing Brownian motion in flat lipid membranes and spherical vesicles [3,5,6] as well as in liquid crystal films [7,8], with the mobility of the inclusions calculated from the diffusion coefficient by means of the Einstein relation. This approach requires a model describing the relation between the mobility and such physical parameters as the inclusion size and the viscosities of the membrane and the surrounding fluid.…”

mentioning

confidence: 99%

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Two-Dimensional Microrheology of Freely Suspended Liquid Crystal Films

et al. 2011

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confidence: 90%

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confidence: 99%

Two-Dimensional Microrheology of Freely Suspended Liquid Crystal Films

et al. 2011

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“…These fluid films are unique among monolayer liquid systems in that they are in a symmetric environment with vapor on both sides. Such substrate-free monolayer fluid molecular films are of fundamental interest in soft matter nanoscience, serving as fluid systems of reduced dimensionality for the study of fluctuation, symmetry, and interface effects (9,10). Here we show that single and few layer smectic films can be used to measure the surface energy of a substrate-free fluid molecular monolayer.…”

mentioning

confidence: 76%

Surface energetics of freely suspended fluid molecular monolayer and multilayer smectic liquid crystal films

Nguyen

Park

Pang

et al. 2012

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

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A study of the surface energetics of the thinnest substrate-free liquid films, fluid molecular monolayer and multilayer smectic liquid crystal films suspended in air, is reported. In films having monolayer and multilayer domains, the monolayer areas contract, contrary to predictions from the van der Waals disjoining pressure of thin uniform slabs. This discrepancy is accounted for by modeling the environmental asymmetry of the surface layers in multilayer films, leading to the possibility that preferential end-for-end polar ordering of the rod shaped molecules can reduce the surface energy of multilayers relative to that of the monolayer, which is inherently symmetric.fluid film | liquid crystals T he attractive Van der Waals interaction makes it possible for the existence of the liquid phase, which, at a temperature lower than the critical temperature, can coexist and share an interface with a gas phase that has different structure and properties (1). At this interface, the density changes across a distance on the order of the intermolecular distance of the liquid, resulting in a difference between the tangential stress and the normal pressure which generates the surface tension, equal to the excess surface energy (2, 3). It is thus interesting to study the surface energetics and tension in ultra-thin films in which the density and the normal pressure inside the liquid are not those of the bulk. These differences become larger as film thickness becomes smaller, so ultrathin films are of interest. However, liquid films in air thinner than h ≈ 2.5 nm rupture via spontaneous pore formation due to surface tension (4). Thus, in order to be stable against rupture, films must be internally structured to suppress thinning and maintain h ≥ 2.5 nm.Fluid smectic liquid crystals (LCs) are three dimensional (3D) phases of rod shaped molecules organized into periodic stackings of molecular layers, where each layer is a 2D liquid. At the air/LC interface, the smectic layering exhibits a strong tendency for the layers to be parallel to the interface, and thus for the molecules at the interface to be in the same smectic layer, typically of thickness d ≈ 3 nm. This organization enables the formation and stabilization of freely suspended smectic films consisting of an integral number, N, of smectic layers, where, for some materials, N can be as small as N ¼ 1, that is, fluid monolayers stable for extended periods have been made in several different materials (5,6,7,8). These fluid films are unique among monolayer liquid systems in that they are in a symmetric environment with vapor on both sides. Such substrate-free monolayer fluid molecular films are of fundamental interest in soft matter nanoscience, serving as fluid systems of reduced dimensionality for the study of fluctuation, symmetry, and interface effects (9, 10). Here we show that single and few layer smectic films can be used to measure the surface energy of a substrate-free fluid molecular monolayer.In smectic layers, the molecular long axes are narrowly distributed in...

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“…The experiment provides a set of reliable data against which further theoretical modeling can be developed. It is also relevant to a class of problems related to the mobility and microrheology of interfacial particles in a monolayer or membrane, such as lipid or proteinassociated domains in cell membranes [24][25][26].…”

Section: Prl 111 168304 (2013) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

“…When the Saffman length [23,24] S ¼ s = b ) h (large s regime), the effect of the liquid subphase is negligibly small and the HIs are essentially 2D [25,26]. In this case, C rr is expected to depend logarithmically on r [23,27].…”

mentioning

confidence: 99%