Laser induced periodic structure on lecithin-doped polyimide film surface and its ability to align liquid crystal molecules

Doping effect of lecithin in polyimide (PI) films on the preparation of laser induced periodic structure (LIPS) was investigated using single-beam polarized pulse UV laser. We found that the regularity of LIPS on lecithin-doped PI film irradiated at 266 nm was better than that at 355 nm and the threshold energy for the preparation of LIPS decreased. The amplitude of LIPS increased with the increase of lecithin content. In addition, lecithin molecules tended to migrate to the film surface after laser irradiation according to FT-IR spectroscopic results. We found that nematic liquid crystal molecules were azimuthally aligned on the irradiated doped PI surface when lecithin content was below 20 wt%, and were vertically aligned when the lecithin content was 30 wt%.