[en] Spheres of cholesteric liquid crystal generate dynamic patterns due to selec- tive reflection from a helical structure subject to continuously curved bounda- ries. So far the patterns are investigated exclusively as function of reflections at the sphere exterior. Here it is shown that the cholesteric shells in a microfluidics produced double emulsion enable also a sequence of internal reflections if the shells have sufficiently thin top and thick bottom. While such asymmetry is promoted by buoyancy when the internal droplet has lower density than the liquid crystal, the elasticity of the cholesteric helix prefers
a symmetric shell geometry, acting against gravity. This subtle balance can hide the internal reflections for long time. Eventually, however, the asymmetry is established, revealing a new class of photonic patterns characterized by colored sharp concentric rings. With the complete knowledge of the diverse light-reflecting behavior of cholesteric liquid crystal shells, and utilizing the tunability of the structure period by, e.g., temperature, electric field, or expo- sure to various chemical species as well as polymer stabilization for making the shells long-term stable, they may be developed into remarkable new optical elements for photonics, sensing, or security pattern generation.
Disciplines :
Physics
Author, co-author :
GENG, Yong ; University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit
Jang, Ju-Hyun; Kyungpook National University > School of Applied Chemical Engineering
Noh, Kyung-Gyu; Kyungpook National University > School of Applied Chemical Engineering
NOH, Junghyun ; University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit
LAGERWALL, Jan ; University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit
Park, Soo-Young; Kyungpook National University > School of Applied Chemical Engineering
External co-authors :
yes
Language :
English
Title :
Through the Spherical Looking-Glass: Asymmetry Enables Multicolored Internal Reflection in Cholesteric Liquid Crystal Shells
Publication date :
20 November 2017
Journal title :
Advanced Optical Materials
eISSN :
2195-1071
Publisher :
Wiley
Volume :
6
Issue :
1
Pages :
1700923
Peer reviewed :
Peer Reviewed verified by ORBi
Focus Area :
Physics and Materials Science
European Projects :
H2020 - 648763 - INTERACT - Intelligent Non-woven Textiles and Elastomeric Responsive materials by Advancing liquid Crystal Technology