The emergence of memory in liquid crystals

The nematic phase of liquid crystals (LC), used in most LC display applications, is a fluid state formed by orientationally ordered molecules. The direction of their alignment, and hence the overall optical response of the material, is easily modified by the application of an electric field and elastically relaxes back to a well-defined off-state when the field is removed. It has been recently shown that hybrid materials formed by nematic LCs incorporated in complex micro-structured porous matrices are often capable of indefinitely retaining the alignment direction imposed by an electric field. Such multistability is ultimately due to the interactions of the porous material with the lines of topological defects that develop within the confined nematic. Controlling the defect lines and their interactions is crucial to the design of materials whose optical properties are electrically driven but spontaneously preserved.