Spatially periodic patterns of flexoelectric origin in twisted nematic layers with negative dielectric anisotropy

ABSTRACT

The deformations induced by an electric field in nematic liquid crystal layers can be homogeneous (i.e. one-dimensional) or spatially periodic (i.e. two-dimensional). The periodic deformations take the form of parallel stripes visible under a microscope. They are particularly favoured when the nematic material possesses flexoelectric properties. In the present paper, numerical studies of the stripes arising in twisted nematic cells are described. The layers of the model mixture of calamitic and bent-core nematic were simulated. Negative dielectric anisotropy was assumed as a source of stabilising torques acting on the director. The results of simulations showed that sufficiently strong flexoelectricity prevails over the influence of negative dielectric anisotropy and causes arising of stripes. The structure of stripes was determined by means of director distributions calculated for the cross-sections of single stripes. The ranges of dielectric anisotropy and of flexoelectric parameter, for which the periodic patterns appeared, were determined.

Graphical abstract

KEYWORDS:

• Nematics
• flexoelectricity
• director deformations
• periodic patterns

Disclosure statement

No potential conflict of interest was reported by the author(s).