Kinetics of motile solitons in nematic liquid crystals

Abstract

The generation of spatially localized, soliton-like hydrodynamic disturbances in microscale fluidic systems is an intriguing challenge. Herein, we introduce nonequilibrium solitons in nematic liquid crystals stimulated by an electric field. These dynamic solitons are robust as long as the electric field is maintained. Interestingly, their kinetic behaviours depend on the field condition-Tuning of the amplitude and frequency of the applied electric field alters the solitons to self-assemble into lattice ordering like physical particles or to command them to various dynamic states. Our key property to the realisation is the electrohydrodynamic instability due to the coupling between the fluid elasticity and the background convection. This paper describes a new mechanism for realising dynamic solitons in fluid systems on the basis of the electrohydrodynamic phenomena.

Dynamics of electrically driven solitons in nematic and cholesteric liquid crystals

“…3d and Supplementary Fig. 6) which may be attributed to the localization of ions 31 . Another explanation may be the surface roughness of the indium tin oxide (ITO) electrode layer, leading locally to higher inhomogeneous electric fields.…”

“…We show that novel soliton-like features are induced by chirality. Unlike the features in NLCs reported before [29][30][31] , the solitons in CLCs show more complex interactions and behave similar to a wave-particle dualism in so far that they either "pass through" each other without losing identity (solitary wave) or collide with each other and undergo reflection (hard particle). Furthermore, we show that the trajectories of their motion can be controlled by a predesignated alignment pattern allowing the realization of microcargo transport by soliton motion.…”

“…In addition, in ref. 31 , the authors also claim that the far-field background flow may also contribute to the traveling velocity. However, in our experiments, the convective flow usually occurs at relatively high amplitudes of electric fields and we anticipate that this does not significantly contribute here.…”

“…In a nematic phase, two nematic solitons moving toward each other can collide (overlap spatially and interact nonlinearly) and then "pass through" each other without losing their identity. The collision behavior is slightly different and depends on the degree of offset, Δx pre (the distance between the centers of the two solitons along the x-axis) [29][30][31] . But the most frequent scenario is that the two solitons moving along the y-axis coalesce and form a perturbation during the collision.…”

“…Very recently, the so-called (3 + 2)D solitons, where "3" refers to the 3D spatial self-confinement and "2" specifies propagation directions that are either perpendicular or parallel to the alignment direction, were observed in a NLC by Lavrentovich et al 29,30 . These formations are nonsingular bow-like director perturbations that propagate rapidly through a slab of a uniformly aligned NLC and survive collisions with each other 30,31 . It should be noted that a similar phenomenon was earlier observed by Brand et al 32 , who reported localized formations in the shape of "butterflies" that could move in the plane of the cell.…”