Photo-patterned memory state based on nematic-silica-dye suspension

Abstract

The influence of photoalignment on the memory state of nematic liquid crystals (LCs) doped with silica nanoparticles and azo dyes was studied. The memory state of the LC sample with hybrid alignment was realized with electrophoretically controlled silica nanoparticles, which accumulated on the homogeneously aligned side of the LC sample to stabilize the vertical orientation of LC molecules through a pulse voltage with appropriate polarity. When the photoalignment was executed on the LCs in the hybrid orientation, the adsorbed azo dyes screened the effect of vertical orientation supported by silica networks. The hybrid LC orientation was stabilized because the adsorbents of azo dyes on the substrate provided a stronger surface homogeneous alignment. When the LCs in the memory state of vertical alignment were illuminated, their vertical orientation was maintained by the adsorbed azo dyes that suppressed the electrophoretic movement of the silica nanoparticles. The study also demonstrates a simple display with hidden images by utilizing these results.