Application of buckypaper for preserving cholesteric liquid crystal cells within a certain temperature range

• Published in: Optical materials express Vol. 4; no. 4; pp. 719 - 724
• Main Authors: Ma, Hao-Kang, Chien, Ping-Cheng, Tsai, Min-Cheng, Miao, Hsin-Yuan, Liu, Jih-Hsin, Huang, Chia-Yi
• Format: Journal Article
• Language: English
• Published: 01.04.2014
• Subjects: Attenuators; Cholesteric liquid crystals; Constants; Cooling; Electric potential; Heating; Reflection; Voltage
• ISSN: 2159-3930; 2159-3930
• DOI: 10.1364/OME.4.000719

Application of buckypaper to cholesteric liquid crystals (CLCs) is demonstrated. The buckypaper functions as a thin film resistant heater and a near-perfect absorber in this study. A planar CLC cell with buckypaper pasted onto one of its surfaces is used to develop a voltage-induced optical attenuator. The intensity of the reflection band of the CLC attenuator can decrease (increase) by the application (removal) of a single-pulse voltage, and the wavelength of the reflection band remains constant as the reflection intensity decreases (increases). The decrease in the reflection intensity is attributable to the cholesteric arrow right -isotropic phase transition of the LCs via heating of the buckypaper, and absorption by the black buckypaper. The increase in the reflectance results from the isotropic arrow right cholesteric phase transition of the LCs through cooling of the environment. During cooling, the application of a low DC voltage to the buckypaper can keep the cell temperature constant because thermal equilibrium between the heating of the buckypaper and the cooling of the environment is established. Using this method, the blue phase of a CLC cell can stably exist for more than an hour at room temperature, without the need for a temperature stage, polymer materials or particular LCs.