Twist localizes three-dimensional patterns

Rossberg, Axel G.

doi:10.1103/physreve.62.4682

Cited by 3 publications

(3 citation statements)

References 18 publications

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“…In order to test if the twisted anchoring used in our experiment can cause a higher value of C 1 , we analyzed a model for the z dependence of director twist φ(z) and convection mode Â(z) and their interaction [30,35]. Keeping only terms that are relevant for determining C 1 , the model reads in appropriate dimensionless units…”

Section: The Effect Of the Twisted Anchoring On Cmentioning

confidence: 99%

“…In our experiments, the conventional EC setup was modified by twisting the nematic within the layer: Instead of anchoring the nematic director at the surfaces of the layer parallel to the x axis, the anchoring direction is rotated by a fixed angle in opposite directions at the two surfaces [25,26,27,28]. This geometry seems to be favorable for PJL.…”

Section: Introductionmentioning

confidence: 99%

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Observation of stable phase jump lines in convection of a twisted nematic liquid crystal

2006

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We report observations of stable, localized, linelike structures in the spatially periodic pattern formed by nematic electroconvection, along which the phase of the pattern jumps by pi. With increasing electric voltage, these lines form a gridlike structure that goes over into a structure indistinguishable from the well-known grid pattern. We present theoretical arguments that suggest that the twisted cell geometry we are using is indirectly stabilizing the phase jump lines, and that the phase jump lines lattice is caused by an interaction of phase jump lines and a zig-zag instability of the surrounding pattern.

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Section: The Effect Of the Twisted Anchoring On Cmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Observation of stable phase jump lines in convection of a twisted nematic liquid crystal

2006

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“…Based on the reduced 3D description derived here, the linear theory for this configuration is developed in Ref. [63].…”

Section: Variation Of the Boundary Conditionsmentioning

confidence: 99%

Three-dimensional pattern formation, multiple homogeneous soft modes, and nonlinear dielectric electroconvection

Rossberg

2000

Phys. Rev. E

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Patterns forming spontaneously in extended, three-dimensional, dissipative systems are likely to excite several homogeneous soft modes ( approximately hydrodynamic modes) of the underlying physical system, much more than quasi-one- (1D) and two-dimensional (2D) patterns are. The reason is the lack of damping boundaries. This paper compares two analytic techniques to derive the pattern dynamics from hydrodynamics, which are usually equivalent but lead to different results when applied to multiple homogeneous soft modes. Dielectric electroconvection in nematic liquid crystals is introduced as a model for 3D pattern formation. The 3D pattern dynamics including soft modes are derived. For slabs of large but finite thickness the description is reduced further to a 2D one. It is argued that the range of validity of 2D descriptions is limited to a very small region above threshold. The transition from 2D to 3D pattern dynamics is discussed. Experimentally testable predictions for the stable range of ideal patterns and the electric Nusselt numbers are made. For most results analytic approximations in terms of material parameters are given.

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Three-dimensional imaging of dielectric patterns in electrohydrodynamic convection of a nematic liquid crystal

et al. 2006

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The transition from surface to bulk normal dielectric rolls in a nematic liquid crystal is imaged by fluorescence confocal polarizing microscopy. The three-dimensional director structure and the liquid flow are scanned in both the layer plane and the transverse plane. Two systems of small-scale convective flow are formed, one at each electrode. Strong anchoring makes director oscillations difficult and charges accumulate by the Carr-Helfrich mechanism. The middle region is a structureless convection where the director oscillates with the frequency of the applied voltage. The small-scale flow eventually fills the cell from one electrode to the other as one system of thin and elongated rolls. The true dielectric mode is not a director pattern, rather a surface flow instability.

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Twist localizes three-dimensional patterns

Cited by 3 publications

References 18 publications

Observation of stable phase jump lines in convection of a twisted nematic liquid crystal

Observation of stable phase jump lines in convection of a twisted nematic liquid crystal

Three-dimensional pattern formation, multiple homogeneous soft modes, and nonlinear dielectric electroconvection

Three-dimensional imaging of dielectric patterns in electrohydrodynamic convection of a nematic liquid crystal

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