Cylindrical nematic liquid crystal shell: effect of saddle-splay elasticity

Abstract

We realize cylindrical nematic liquid crystal shells and investigate their director configurations thoroughly focusing on the role of saddle-splay elasticity.

Interpretation of saddle-splay and the Oseen-Frank free energy in liquid crystals

“…This expression shows that all four of the modes cost different amounts of elastic free energy. The elastic constant for (double) splay is (K 11 − K 24 ), the elastic constant for (double) twist is (K 22 − K 24 ), the elastic constant for bend is K 33 , and the elastic constant for the mode ∆ is 2K 24 . The simple approximation of equal elastic constants then corresponds to K 11 = K 22 = K 33 = 2K 24 ≡ K.…”

“…This variation reduces the S and increases the ∆, compared with the uniform state. Hence, that variation reduces the free energy compared with the uniform state, provided that (K 11 − K 24 ) > K 24 .…”

“…Surprisingly, there are certain liquid crystal materials that violate the Ericksen inequalities, and actually exhibit K 22 < K 24 . In particular, several studies have investigated the lyotropic chromonic liquid crystals Sunset Yellow (SSY) and disodium cromoglycate (DSCG) in cylindrical capillaries [9,22,23] or cylindrical shells [24]. Experimentally, those studies show that the uniform, achiral state can become unstable to the formation of a chiral state.…”

Responsive Liquid‐Crystal‐Clad Fibers for Advanced Textiles and Wearable Sensors

“…[14] Upon application as a uniform film, the LC cladding film will quickly break into beads. [15][16][17][18] This occurs in about 3 s for nematic LCs with low viscosity, and about 50 s for the more viscous CLCs. Drawing the LC clad fiber through an aqueous solution of polymer, such as polyvinylpyrrolidone (PVP) that is immiscible with the LC before the beading occurs, stabilizes the cladding.…”

“…Upon application as a uniform film, the LC cladding film will quickly break into beads . This occurs in about 3 s for nematic LCs with low viscosity, and about 50 s for the more viscous CLCs.…”