Light‐Driven Electrohydrodynamic Instabilities in Liquid Crystals |
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| Authors: | Yuanyuan Zhan Albertus P H J Schenning Dirk J Broer Guofu Zhou Danqing Liu |
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| Affiliation: | 1. SCNU‐TUE Joint Lab of Device Integrated Responsive Materials (DIRM), National Center for International Research on Green Optoelectronics, South China Normal University, Guangzhou, P. R. China;2. Laboratory of Functional Organic Materials and Devices (SFD), Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, AE Eindhoven, The Netherlands;3. Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, AE Eindhoven, The Netherlands;4. Shenzhen Guohua Optoelectronics Tech. Co. Ltd., Shenzhen, China |
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| 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. |
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| Keywords: | electrohydrodynamic instabilities light scattering liquid crystals photochemistry |
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