Homeotropic liquid crystal alignments through periodically unidirectional nano-wedges patterned by nanoimprint lithography

This study demonstrates the fabrication of periodically unidirectional nano-wedges using nanoimprint lithography to achieve homeotmpic alignments in sandwiched liquid crystal (LC) cells. When electrically operating LC cells for the purpose of electro-optical performance without the occurrence of disclination lines, the LC pretilt angles play an essential role in achieving uniform LC alignments and well-behaved device functions. The periodical nano-wedges composed of asymmetrically sawtooth-like units were just designed for providing LC pretilt angles. We used grayscale electron beam lithography to fabricate nanoimprint master templates with periodically unidirectional nano-wedges with a 1-mu m pitch. The photoresist SU-8 was used as the nanoimprint polymer to form nano-wedge structures. An ultrathin poly(dimethylsiloxane) (PDMS) film was coated on the nano-wedges to assist homeotropic LC alignments. The fabricated nano-wedges were capable of better LC alignments than nanorectangles in the cells, including fewer disclination lines and better optical performance, as supported by the data obtained.

Automated summary

This study demonstrates the fabrication of periodically unidirectional nano-wedges using nanoimprint lithography to improve LC alignments and optical performance in sandwiched LC cells. The experiment results show that nano-wedge structures can achieve better LC alignments and fewer disclination lines than nanorectangles in the cells.