Patterned alignment of liquid crystals

In this study the m-rubbing technique is used to micropattern polyimide alignment layers using a metallic sphere at different loads. Optical and at. force microscopy shows that the width of the patterns ranges from 12-40 mm and depth ranges from 2-14 nm. The authors primary finding is that m-rubbing induces planar alignment in polyimides. The authors performed m-rubbing on pre-rubbed polyimide perpendicular to the rubbing direction. It is found that m-rubbing erases the alignment properties of the pre-rubbing procedure. Liq. crystal cells were constructed using the pre-rubbed polyimide substrates with m-rubbed patterns on one side and a homogeneously rubbed polyimide layer on the other side. Therefore the pre-rubbed polyimide layers are crossed and consequently a twisted nematic alignment is obsd. outside the micro-patterns. Within the micro-patterns, the directions of the pre-rubbing and m-rubbing are parallel, a planar alignment obsd. In another configuration, liq. crystal cells were made with pre-rubbed polyimide substrates having micro-patterns on both sides to give grid pattern with planar and twisted nematic configuration. Studies were extended to det. the pretilt of the micro patterned area