| 摘要 |
<p>A method of controlling a helicoidal liquid crystal material wherein the liquid crystal material has a negative dielectric anisotropyΔεsatisfyingΔε=εΜ-εχ< 0, whereεΜis the dielectric constant parallel to the helical axis of the liquid crystal material andε± is the dielectric constant perpendicular to the helical axis of the liquid crystal material, such that in a state without flexoelectric coupling the material has a lowest energy alignment state in which the helical axis is aligned parallel to an applied electric field. The liquid crystal material can undergo flexoelectric coupling with an applied electric field as a result of an effective dielectric constantεeffective perpendicular to the helical axis given byεeffective =εflexo + (ε,, +ε⊥)/2 >ε⊥, whereεflexo is a contribution from flexoelectric polarisation in the material, such that in a state with flexoelectric coupling the material has a lowest energy alignment state in which the helical axis is aligned perpendicular to an applied electric field. The method comprises applying an electric field to the material and changing one or more parameters of the electric field so as to enable or suppress said flexoelectric coupling and thereby switch the material between lowest energy alignment states in which the helical axis is aligned either perpendicular or parallel to the applied electric field.</p> |
