Yc Jeong

Optically tunable and reconfigurable azobenzene photonic crystal

The generation of three-dimensional (3D) nanoporous materials with methods that allow control of the shape and size is an important issue owing to its numerous applications to the areas of material sciences and nanophotonics. However, the methods typically used for fabricating nanoporous structures, such as self-assembly, direct writing, and interference lithography, cannot modify the structural morphologies much over a large area at the same time. In this work, we prepare azobenzene-based oligomer films with controllable pore sizes and shapes by means of directional photofluidization lithography. This strategy by using the photo-reconfiguration of oligomers enables an unprecedented degree of precise manipulation of structural features and the generation of hierarchical porosity in a three-dimensionally interconnected network.

Photo-configurable embossed liquid crystal alignment layer with high azimuthal anchoring strength.

Herein we describe a photo-alignment layer of improved azimuthal anchoring energy comparable to conventional rubbing method. In order to address the inherent low anchoring stability of photo-alignment layer, we applied embossing technique to conventional photosensitive polymer film, based on the cinnamoyl photoreactive groups, to introduce physical micro-groove effect for additional anchoring energy. From this, 2.5 × 10⁻⁴ J/m² of azimuthal anchoring energy was achieved, which is considered as synergistic effect from both photoinduced chemical interaction and physical microgroove alignment. In this study, we conducted systematic study on change in anchoring energy as a function of both aspect ratio of embossed pattern and UV exposure dose. We also demonstrated fabrication of sophisticated multi-domain structure of LC cells and discussed theoretical interpretation through LC simulation.