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Light‐Driven Electrohydrodynamic Instabilities in Liquid Crystals
Author(s) -
Zhan Yuanyuan,
Schenning Albertus P. H. J.,
Broer Dirk J.,
Zhou Guofu,
Liu Danqing
Publication year - 2018
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201707436
Subject(s) - electrohydrodynamics , spiropyran , merocyanine , materials science , liquid crystal , homeotropic alignment , light scattering , photochromism , chemical physics , electric field , optics , optoelectronics , light field , nanotechnology , scattering , chemistry , physics , quantum mechanics
Abstract The induction of electrohydrodynamic instabilities in nematic liquid crystals through light illumination are reported. For this purpose, a photochromic spiropyran is added to the liquid crystal mixture. When an electrical field is applied in the absence of UV light, the homeotropic liquid crystal reorients perpendicular to the electrical field driven by its negative dielectric anisotropy. Upon exposure to UV light, the nonionic spiropyran isomerizes to the zwitterionic merocyanine form inducing electrohydrodynamic instabilities which turns the cell from transparent into highly scattering. The reverse isomerization to closed‐ring spiropyran form occurs thermally or under visible light, which stops the electrohydrodynamic instabilities and the cell becomes transparent again. It is demonstrated that the photoionic electrohydrodynamic instabilities can be used for light regulation. Local exposure, either to drive the electrohydrodynamics or to remove them enables the formation of colored images.