Control of Toric Focal Conic Domain(TFCD) arrangement by Multidirectional Rubbing

Abstract

With antagonistic anchoring conditions (random planar at the substrate interface and homeotropic at air interface) smectic-A liquid crystals form toric focal conic domains (TFCDs). Controlling the arrangement of TFCDs is interested in photonic applications such as microlens array and photomask. In previous research, our group achieved highly ordered hexagonal array of TFCDs with confined micro-channels and surface treatment of planar polymer coating. In this study, we could obtain square array of TFCDs by cross-directional rubbing method. Polyimide (PI) coated glass substrate is rubbed in two perpendicular directions and 8CB (4-cyano-4’-octyl-byphenyl) smectic-A liquid crystal was casted on the rubbed substrate. Texture of TFCDs square array is observed by polarized optical microscopy (POM). We searched the range of optimal rubbing strength condition about two perpendicular directions and investigated formation mechanism of square array of TFCDs.