Thermal and flexoelectric effects on nematodynamics in a microvolume cylindrical cavity

Electrically Driven Torsional Distortions in Twisted Nematic Volumes

The purpose of this review is to describe the physical mechanism responsible for the appearances of both traveling and non-traveling distortions in a twisted microsized nematic volume under the effect of a large electric field. Both experimental and theoretical works devoted to the excitation of structured periodic domains in initially homogeneously aligned liquid crystal systems under the effects of strong crossed electric and magnetic fields were analyzed. Electrically driven distortions in the microfluidic nematic capillary in the presence of a temperature gradient in it, based on the number of numerical results, were analyzed. We also focus on the description and explanation of the novel mechanism of excitation of the kink- and π-like distortion waves of the director field n^ in a cylindrical nematic micro-volume under the effect of voltage U and temperature gradient ∇T, set up between the cooler inner and hotter outer cylinders. Electrically driven torsional distortions in twisted nematic micro-volumes in the form of the kink-like running front based on the classical Ericksen–Leslie approach were considered.

Nanofluidics of nematic liquid crystals in hollow capillaries

The aim of this paper is to investigate the response of a homogeneously aligned nematic nanosized hollow cavity (HANNHC) confined between two charged horizontal coaxial cylinders and subjected to both a radially applied electrostatic field E, arising from the surface charge density κ and the temperature gradient ∇T set between these cylinders. This was done within the framework of an extension of the classical Ericksen-Leslie theory, supplemented by thermomechanical correction of the shear stress and Rayleigh dissipation function, as well as taking into account the entropy balance equation. The physical mechanism responsible for the excitation of the hydrodynamic flow in the HANNHC is based on the interaction of the director and temperature gradients and the static electric field. Calculations show that under the influence of both the ∇T and E, a stationary flow u^{st} is excited in the HANNHC in the horizontal direction. It is shown that the electric force enforced by the flexoelectric polarization plays a crucial role in the excitation of u^{st} between these cylinders.

Molecular organization of nematic liquid crystals between concentric cylinders: role of the elastic anisotropy

The orientational order in a nematic liquid crystal sample confined to an annular region between two concentric cylinders is investigated by means of lattice Monte Carlo simulations. Strong anchoring and homeotropic orientations, parallel to the radial direction, are implemented at the confining surfaces. The elastic anisotropy is taken into account in the bulk interactions by using the pair potential introduced by Gruhn and Hess [T. Gruhn and S. Hess, Z. Naturforsch. A 51, 1 (1996)] and parametrized by Romano and Luckhurst [S. Romano, Int. J. Mod. Phys. B 12, 2305 (1998); Phys. Lett. A 302, 203 (2002); G. R. Luckhurst and S. Romano, Liq. Cryst. 26, 871 (1999)], i.e., the so-called GHRL potential. In the case of equal elastic constants, a small but appreciable deformation along the cylinder axis direction is observed, whereas when the values of K(11)/K(33) if K(22)=K(33) are low enough, all the spins in the bulk follow the orientation imposed by the surfaces. For larger values of K(11)/K(33), spontaneous deformations, perpendicular to the polar plane, increase significantly. Our findings indicate that the onset of these deformations also depends on the ratio K(22)/K(33) and on the radius of the cylindrical surfaces. Although expected from the elastic theory, no tangential component of the deformations was observed in the simulations for the set of parameters analyzed.