Browsing by Author "Chen, Chao-Yuan"

Now showing 1 - 7 of 7

Chiral-induced self-assembly sphere phase liquid crystal with fast switching time
(2014-03-03)
Zhu, Ji-Liang
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Ni, Shui-Bin
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Chen, Chao Ping
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Wu, Dong-Qing
;
Song, Xiao-Long
A fluid self-assembly sphere phase (SP) of liquid crystal induced by chiral dopant is observed in a narrow temperature range between isotropic and blue phase or between isotropic and chiral nematic phase. The SP consists of three-dimensional twist spheres (3-DTSs) and disclinations among 3-DTSs. The temperature range of the SP has been broadened to more than 85 degrees C by stabilizing the disclinations with amorphous polymer chains. The electro-optical switching time of the polymer-stabilized SP is demonstrated in sub-millisecond with a low switching electric field of 4.4 V mu m(-1), which is of promising applications in displays, 3-D tunable photonic crystals, and phase modulators. (C) 2014 AIP Publishing LLC.
Dye-liquid-crystal-based biosensing for quantitative protein assay
(2018-03-01)
Wu, Po-Chang
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Karn, Abhishek
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Lee, Mon-Juan
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Lee, Wei
;
Chen, Chao-Yuan
Dye liquid crystals (DLCs) have been extensively investigated in the field of liquid crystal display, but their potential in biosensing has not been explored. To provide insights into the potential of DLCs as a means of biosensing material, a DLC-based biosensor was developed for protein detection and quantitation. Unlike dye doped LCs, the DLC used in this study contains an azobenzene LC molecule chemically modified with two azo groups as chromophores, enabling the DLC to exhibit unique optical anisotropy and dichroic absorption at 470 rim, which were exploited in the quantitation of bovine serum albumin (BSA). The change in orientation of DLC molecules from the homeotropic to a disrupted state by BSA immobilized on the aligning-layer surface was evaluated in terms of the relative loss in transmittance, expressed by the standard parameter S%, due to the absorption as well as scattering of light. The DLC-based protein assay was capable of determining the BSA concentration, with which S% varied linearly between 1 mu g/ml and 7.5 mu g/ml. When the DLC molecules were reoriented from a BSA-disrupted state to the homeotropic alignment by an externally applied electric field, a linear correlation between S% and BSA concentration could be also derived from the voltage transmittance plots. The unique electro-optical properties of the intrinsically dichroic DLC are promising toward the development of a simple and reliable sensing platform for the quantitative analysis of biomolecules.
Immunoassays for the cancer biomarker CA125 based on a large-birefringence nematic liquid-crystal mixture
(2015-01-01)
Sun, Shih-Hung
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Lee, Mon-Juan
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Lee, Yun-Han
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Lee, Wei
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Song, Xiaolong
The use of fluorescence is ubiquitously found in the detection of immunoreaction; though with good sensitivity, this technique requires labeling as well as other time-consuming steps to perform the measurement. An alternative approach involving liquid crystals (LCs) was proposed, based on the fact that an immunocomplex can disturb the orientation of LCs, leading to an optical texture different from the case when only antigen or antibody exists. This method is label-free, easy to manipulate and lowcost. However, its sensitivity was low for practical usage. In this study, we adopted a high-birefringence liquid crystal (LC) to enhance the sensitivity for the immunodetection. Experiments were performed, targeting at the cancer biomarker CA125. We showed that the larger birefringence (Delta n = 0.33 at 20 degrees C) amplifies the detected signal and, in turn, dramatically improves the detection limit. To avoid signal loss from conventional rinsing steps in immunodetection, CA125 antigen and antibody were reacted before immobilized on substrates. We studied the specific binding events and obtained a detection limit as low as 1 ng/ml. The valid temperature ranges were compared by using the typical single-compound LC 5CB and the high-birefringence LC mixture. We further investigated time dependency of the optical textures and affirmed the capability of LC-based immunodetection in distinguishing between specific and nonspecific antibodies.
Low-Power Displays With Dye-Doped Bistable Chiral-Tilted Homeotropic Nematic Liquid Crystals
(2014-12-01)
Lee, Yun-Han
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Huang, Kuan-Chung
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Lee, Wei
;
Chen, Chao-Yuan
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光電系統研究所
Energy-efficient display has been drawing much attention in recent years due to the prevailing of mobile devices as well as the rising environmental concerns. A chiral nematic system with appropriately configured pre-tilted angle and pitch length is capable of switching between the twist-like and homeotropic-like states with the merit of bistability. Introducing dichroic dyes into this system, we demonstrated a bistable scheme of liquid-crystal display without the need of polarizers.
Temperature-dependent optical constants and birefringence of nematic liquid crystal 5CB in the terahertz frequency range
(2008-05-01)
Pan, Ru-Pin
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Hsieh, Cho-Fan
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Pan, Ci-Ling
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Chen, Chao-Yuan
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電子物理學系
We have measured the frequency dependence and temperature dependence of the optical constants of a liquid crystal 4(')-n-pentyl-4-cyanobiphenyl (5CB) in both nematic and isotropic phases by using terahertz time-domain spectroscopy. The extinction coefficient of 5CB is less than 0.02 and without sharp absorption features in the frequency range of 0.2-1.0 THz. The extraordinary and ordinary indices of refraction at 25 degrees C are around 1.77 and 1.58, respectively, giving rise to a birefringence of 0.20 +/- 0.02 in this frequency range. The temperature-dependent order parameter extracted from birefringence agrees with the results from the visible region quite well. (C) 2008 American Institute of Physics.
Terahertz phase shifter or retarder based on magnetically controlled birefringence in liquid crystals
(2005-02-03)
Pan, Ci-Ling
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Chao, Ru-Pin
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Chen, Chao-Yuan
The present invention enables a means of continuously shifting the phase of electromagnetic waves in the THz (0.1 to 10 THz, 1 THz=10−12 Hz) or sub-millimeter wave range. It is based on magnetically controlled birefringence of liquid crystals. The device consists of an assembly of a liquid crystal cell and rotatable magnets. By varying the angle of the magnet with respect to the incident THz wave, desired phase shift or delay can be achieved. To increase the amount of phase shift, the device employs multiple liquid crystal cells in a compact sandwich structure.
TUNABLE TERAHERTZ WAVELENGTH SELECTOR DEVICE USING MAGNETICALLY CONTROLLED BIREFRINGENCE OF LIQUID CRYSTALS
(2009-01-01)
Chao, Ru-Pin
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Pan, Ci-Ling
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Chen, Chao-Yuan
The present invention provides a tunable terahertz (THz) wavelength selector device, which includes a fixed phase retarder, a tunable phase retarder and a pair of linear polarizers to form a unit. The fixed phase retarder and tunable phase retarder basically utilizes liquid crystals to provide phase retardation, moreover, utilizing birefringence phenomenon possessed by liquid crystals can provide adequate phase retardation. The fixed phase retarder utilizes horizontal orientation of liquid crystal cell to provide fixed phase retardation, while the tunable phase retarder however utilizes homeotropic liquid crystal cell and a rotatable magnet to provide a tunable phase retardation, wherein the tunable phase retarder can provide the positive or negative phase retardation relative to the fixed phase retarder, based on the direction of the magnet's rotating axes and totally use the entire tunable range into adjusting frequencies which can pass through. Besides, the present invention can also serially connect multiple units described above so as to achieve a narrow enough band-pass bandwidth.