Open AccessTopographically induced homeotropic alignment of liquid crystals on self-assembled opal crystals
Author(s) -
Pankaj Kumar,
Su Yeon Oh,
Vijay Kumar Baliyan,
Sudarshan Kundu,
Seung Hee Lee,
ShinWoong Kang
Publication year - 2018
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.26.008385
Subject(s) - homeotropic alignment , liquid crystal , anchoring , materials science , planar , layer (electronics) , polyimide , optics , molecule , nanotechnology , optoelectronics , chemistry , computer graphics (images) , structural engineering , physics , organic chemistry , computer science , engineering
The surface of multilayered opal crystals resulted in homeotropic alignment of liquid crystal (LC), originated from the surface topography of opal crystals rather than a chemical nature of the nanoparticles. The polar anchoring energy (5.51 × 10 -5 J/m 2 ) of the crystal surface for nematic LC molecules was in a similar range to the conventional polyimide alignment layer (2.11 × 10 -5 J/m 2 ) used for commercial applications. The critical length scale for anchoring transition was approximately Lw = ~1 μm. If a diameter of particle d << 1 μm for opal crystals, LC molecules preferred to anchor vertically to the surface to minimize elastic free energy of bulk LCs. The LC favored a planar anchoring if d >> 1 μm. The results provide crucial insights to understand the homeotropic alignment of LCs on solid surfaces and therefore offer opportunities to develop novel materials for a vertical alignment of LCs.