Multistable polar textures in geometrically frustrated nematic liquid crystals

The ability to manipulate polar entities with multiple external fields could enable functionalities and applications in spin systems, photonics, metamaterials and soft matter. Liquid crystals that exhibit both a crystalline structure and liquid fluidity represent a promising platform for manipulating phases with polar molecular order, notably ferroelectric ones. However, achieving a polar symmetry is challenging with rod-shaped liquid crystal molecules, which form predominantly apolar nematic phases. Here we report an approach in which a geometric lattice confinement of nematic liquid crystals is used to induce planar polar order on the scale of a mesoscopic metamaterial. We confine the nematic liquid crystal in a micropillar array, forming topological defect–pillar pairs of elastic dipoles with a free top interface in contact with an immiscible fluid. The resulting dipole lattice configurations can be programmed rheologically by flowing the top fluid and maintained even after flow cessation, a phenomenon attributed to orientational multistability of the dipoles. This multimemory effect enables the encoding and reconfiguration of directional information. Overall, these results advance our understanding of topological dipoles under confinement and shear flow, enabling the detection, tracking and recording of flow profiles and could facilitate the development of stimuli-responsive materials. Programmable topological dipoles could be used in stimuli-responsive materials. Now it is shown that confinement of an apolar liquid crystal results in controllable polar arrangements of elastic dipoles.