Capillary filling of nematic liquid crystals

Abstract

We studied the orientation of nematic liquid crystals when they were being filled into cells by capillary action. We found that, in the flow front, the liquid crystal was always aligned along the flow direction. Far behind the flow front, the orientation of the liquid crystal depended on the anchoring direction of the alignment layers and the direction and speed of the flow. In cells with the anchoring direction parallel to the flow direction, the liquid crystal always oriented along the flow direction. In cells with the anchoring direction perpendicular to the flow direction, at low flow speed gradients, the liquid crystal orientated uniformly along the anchoring direction; at high flow speed gradients, the liquid crystal in bulk was tilted to the flow direction. The experimentally observed critical flow speed gradient was in agreement with the theoretical prediction.