Topologically non-equivalent textures generated by the nematic electrohydrodynamics
Some classes of nematic liquid crystals can be driven through turbulent regimes when forced by an external electric field. In contrast to isotropic fluids, a turbulent nematic exhibits a transition to a stochastic regime that is characterised by a network of topological defects. We study the deformations arising after the electric field has been switched-off. In contrast to the turbulent regime, the relaxation of this topological-defect regime involves the annihilation of an interlacement of defect lines. We show that these defect lines separate regions of the nematic having topologically non-equivalent textures.
G. Pucci, F. Carbone, G. Lombardo, C. Versace and R. Barberi. Topologically non-equivalent textures generated by the nematic electrohydrodynamics. Liq. Cryst. (2019). full text
Patterns of electro-convection in planar-periodic nematic cells
Nematic liquid crystals are anisotropic fluids that can undergo electro-convective instabilities. These instabilities have been extensively studied for nematics in unidirectional planar alignment. We investigate the electro-convective instability patterns in planar-periodic cells, wherein, in the quiescent situation the nematic undergoes static twist deformations separated by defect lines. We find two regimes that depend on the sample thickness. For large thickness, electro-convective patterns are not affected by the twist, and the samples behave as they were in planar unidirectional alignment. For small thickness, either the convective motion vertically shifts the defect lines or the twist affects the electro-convective domains and resultant curved patterns are observed.
G. Pucci, D. Lysenko, C. Provenzano, Yu. Reznikov, G. Cipparrone and R. Barberi. Patterns of electro-convection in planar-periodic nematic cells. Liq. Cryst. 43:2, 216-221 (2016). full text
G. Pucci, F. Carbone, C. Vena, G. Lombardo, C. Versace and R. Barberi. DSM1-DSM2 Transition Threshold in Turbulent Nematic Mixtures. Mol. Cryst. Liq. Cryst. 614(1), 100-105 (2015). full text
M. P. De Santo, G. Petriashvili, R. Gary, G. Pucci, R. Barberi. Anti-counterfeiting and identification solutions using soft matter. Rend. Fis. Acc. Lincei 26(2):S255-S259 (2015). full text