Electroconvection in smectic C liquid-crystal films visualized by optical anisotropy

Becker, A.; Ried, S.; Stannarius, Ralf; Stegemeyer, H.

doi:10.1209/epl/i1997-00344-9

Cited by 20 publications

(11 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In experiments on smectic A liquid crystal films [4][5][6][7], in which the director was perpendicular to the film, no orientational effects were observed, indicating that the flow remained isotropic in the film plane. Recent experiments on smectic C films [9] showed convection and flow alignment of the projection of the director in the plane of the film, but were not consistent with the Carr-Helfrich mechanism. These were likely driven by the mechanism discussed here, with the flow alignment a secondary effect.…”

Section: Introductionmentioning

confidence: 87%

Weakly nonlinear analysis of electroconvection in a suspended fluid film

Deyirmenjian¹,

Daya²,

Morris³

1997

Phys. Rev. E

View full text Add to dashboard Cite

It has been experimentally observed that weakly conducting suspended films of smectic liquid crystals undergo electroconvection when subjected to a large enough potential difference. The resulting counter-rotating vortices form a very simple convection pattern and exhibit a variety of interesting nonlinear effects. The linear stability problem for this system has recently been solved. The convection mechanism, which involves charge separation at the free surfaces of the film, is applicable to any sufficiently two-dimensional fluid.In this paper, we derive an amplitude equation which describes the weakly nonlinear regime, by starting from the basic electrohydrodynamic equations. This regime has been the subject of several recent experimental studies. The lowest order amplitude equation we derive is of the Ginzburg-Landau form, and describes a forward bifurcation as is observed experimentally. The coefficients of the amplitude equation are calculated and compared with the values independently deduced from the linear stability calculation.

show abstract

Section: Introductionmentioning

confidence: 87%

Weakly nonlinear analysis of electroconvection in a suspended fluid film

Deyirmenjian¹,

Daya²,

Morris³

1997

Phys. Rev. E

View full text Add to dashboard Cite

show abstract

“…[13,31] Other smectic phases form 2D anisotropic fluid films. [31,25,26] Unlike soap films, smectics can flow in the film plane without thickness change and are not susceptible to evaporation. Smectics generally have low electrical conductivity due to residual ionic impurities.…”

Section: Methodsmentioning

confidence: 99%

“…It is also possible to convect other, more complex, smectic phases which are anisotropic in the film plane. [25,26] We will not consider such anisotropy here.…”

Section: Introductionmentioning

confidence: 99%

Electrically driven convection in a thin annular film undergoing circular Couette flow

1999

View full text Add to dashboard Cite

We investigate the linear stability of a thin, suspended, annular film of conducting fluid with a voltage difference applied between its inner and outer edges. For a sufficiently large voltage, such a film is unstable to radially-driven electroconvection due to charges which develop on its free surfaces. The film can also be subjected to a Couette shear by rotating its inner edge. This combination is experimentally realized using films of smectic A liquid crystals. In the absence of shear, the convective flow consists of a stationary, azimuthally one-dimensional pattern of symmetric, counter-rotating vortex pairs. When Couette flow is applied, an azimuthally traveling pattern results. When viewed in a co-rotating frame, the traveling pattern consists of pairs of asymmetric vortices. We calculate the neutral stability boundary for arbitrary radius ratio α and Reynolds number Re of the shear flow, and obtain the critical control parameter Rc (α, Re) and the critical azimuthal mode number mc (α, Re). The Couette flow suppresses the onset of electroconvection, so that Rc (α, Re) > Rc (α, 0). The calculated suppression is compared with experiments performed at α = 0.56 and 0 ≤ Re ≤ 0.22. Fluids, 11, 3613 (1999). See also http://mobydick.physics.utoronto.ca. Physics of

show abstract

“…Such patterns can be prepared, e.g., by mechanical rotation of the film [24], by rotating electromagnetic fields [25][26][27], or by electrically or thermally driven convection [28][29][30]. In absence of droplets, its optical appearance is that of a target pattern of dark and bright rings around the film center.…”

Section: Droplet Interactions and Self-organizationmentioning

confidence: 99%

Self-organization of isotropic droplets in smectic-Cfree-standing films

Völtz

Stannarius

2004

Phys. Rev. E

View full text Add to dashboard Cite

Free standing smectic films have been investigated at the transition from the smectic- C phase to the isotropic phase. In the vicinity of the bulk transition temperatures, isotropic droplets of micrometer size appear in the film. Such systems represent convenient models for anisotropic, two-dimensional emulsions. A characteristic feature of the droplets is their mutual interaction by elastic distortions of the local orientation of the film, the c director, which are related to the anchoring conditions of the c director at the droplet border. We describe in detail the director deformations created by isotropic droplets of different sizes, and their role in the spontaneous organization of regular droplet patterns. Depending upon droplet size and anchoring strength, topological defects can be induced in the c -director field. Qualitative differences to literature data on cholesteric droplets in smectic- C* films are discussed.

show abstract

Electroconvection in smectic C liquid-crystal films visualized by optical anisotropy

Cited by 20 publications

References 22 publications

Weakly nonlinear analysis of electroconvection in a suspended fluid film

Weakly nonlinear analysis of electroconvection in a suspended fluid film

Electrically driven convection in a thin annular film undergoing circular Couette flow

Self-organization of isotropic droplets in smectic-Cfree-standing films

Contact Info

Product

Resources

About