Cholesteric Flakes in Motion Driven by the Elastic Force from Nematic Liquid Crystals

Wei Liu, Yong Zhou, Sunqian Liu, Wan Shao, Dirk J. Broer, Guofu Zhou, Dong Yuan, Danqing Liu

Cholesteric Flakes in Motion Driven by the Elastic Force from Nematic Liquid Crystals

ABSTRACT

The paper presents a methodology to control the motion and orientation of suspended reflective cholesteric flakes in a nematic liquid crystal (LC) matrix. The flakes exhibit a dielectric anisotropy which controls their alignment with their in-plane axes parallel to an external electrical dc field. The elastic forces imposed by the LC host affect the switching behavior of the flakes and take care of the realignment to the planar state as soon as the dc field is switched off. When the LC host has a positive dielectric anisotropy, the switching voltage of the flakes is reduced by a factor of 2 in comparison with a LC host with negative dielectric anisotropy or in comparison with an isotropic host. We discovered that the LC host further regulates the back relaxation of cholesteric to return to the planar state upon retrieving the electric field. Whereas, in the isotropic fluid, flakes do not exhibit a preferred orientation when relaxed. Based on this newly proposed principle, we demonstrated its application as an optical switch for smart windows. Depending on the pitch of the cholesteric helix of the flakes, thelight of a preset wavelength is reflected. Upon application of anelectric field, the embedded flakes rotate their planes perpendicularto the substrate and consequently the incident light becomes fullytransmitted without reflection or scattering of light.


Language English
Journal ACS Applied Materials & Interfaces
Year
2019
Pages 40916-40922
Volume 11
Issue number
43
Status published


KEYWORDS

liquid crystals, nematic elasticity, electric-driven, cholesteric flakes, optical switches


DOI: https://doi.org/10.1021/acsami.9b14650

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  • smart window

    smart window

  • IR reflection

    IR reflection


  • electroresponsive

    electroresponsive


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  • APA
Wei Liu, Yong Zhou, Sunqian Liu, Wan Shao, Dirk J. Broer, Guofu Zhou, Dong Yuan, Danqing Liu. Cholesteric Flakes in Motion Driven by the Elastic Force from Nematic Liquid Crystals. ACS Applied Materials & Interfaces, 2019, 11(43), 40916-40922

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