An Active-Passive Hybrid Control Smart Window based on Cholesteric Liquid Crystal

Guan-Fu Sung^1*, Po-Chang Wu², Wei Lee²

¹College of Photonics, National Yang Ming Chiao Tung University, Tainan, Taiwan
²Institute of Imaging and Biomedical Photonics, National Yang Ming Chiao Tung University, Tainan, Taiwan

* Presenter:Guan-Fu Sung, email:grant.sung418@gmail.com

Cholesteric liquid crystals (CLCs) are important for display and sensing due to their optical and dielectric anisotropy that is susceptible to stimuli such as the electric field and temperature. A CLC in the periodically helical structure is characterized by the selective reflection following Bragg’s law. In this work, an intriguing dual-mode CLC device was manifested, enabling the transparency to be automatically adjustable in response to the temperature while simultaneously allowing a user to take the control in its automation and for fully on-demand function. The principle originates in the voltage-controllable extent of the electrohydrodynamic (EHD) effect in CLC, causing temperature-dependent dynamic scattering and, in turn, the transmission switchable and tunable by the frequency and amplitude of applied voltage. The characteristic Bragg reflection band designated to occur in the near-infrared region offers a value-added benefit to partially reject the undesired thermal radiation in the transparent state.

Keywords: Cholesteric liquid crystals, Smart window, Electrohydrodynamic (EHD) effect, Dynamic scattering, Liquid crystal