ELECTRO-OPTICAL PHENOMENA DUE TO INFLUENCE OF LIGHT BEAMS ON MATERIAL PARAMETERS OF LIQUID CRYSTALS

1999 ◽  
Vol 08 (03) ◽  
pp. 389-401 ◽  
Author(s):  
NELSON V. TABIRYAN ◽  
CESARE UMETON
Keyword(s):  
Liquid Crystals ◽  
Electric Fields ◽  
Diffusion Processes ◽  
Material Parameters ◽  
Ac Electric Fields ◽  
Absorption Of Light ◽  
Optical Phenomena ◽  
Light Beams

Modulation of material parameters of liquid crystals (LC) due to absorption of light beams allows to control the reorientation of the LC under the influence of ac electric fields. Particularly, it makes possible recording of photorefractive-like orientation gratings. Such gratings are phase shifted with respect to the pattern of interfering light beams. The material and external parameters determine the magnitude of the shift. These photorefractive-like phase shifted gratings are stationary, and no diffusion processes are involved in their build-up.

scholarly journals Dynamic FT-IR spectroscopy of liquid crystals and polymer films

1993 ◽  
Author(s):  
Βασίλειος Γρηγορίου
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Electric Fields ◽  
Polymer Films ◽  
Spectroscopic Techniques ◽  
Ac Electric Fields ◽  
Pulsed Dc ◽  
Ft Ir ◽  
Reorientation Dynamics ◽  
Director Reorientation

This dissertation describes the use of continuous-scan and step-scan Fourier transform infrared (FT-IR) spectroscopic techniques to study the dynamics of the response of polymer films and liquid crystals to external perturbations. The investigation of liquid crystals includes both nematic and chiral smectic C examples. In these studies the dynamic infrared absorbance is used to explore the submolecular (functional group) contributions to the reorientation dynamics of the liquid crystal director in response to both pulsed (DC) and modulated (AC) electric fields. Continuous-scan stroboscopic FT-IR and step-scan impulse-response FT-IR were used to analyze the rise dynamics of reorientation resulting from pulsed DC perturbations; whereas step-scan FT-IR was used to monitor both rise and decay processes in response to synchronously modulated (AC) electric fields. In the step-scan measurements this sub-molecular view of the dynamics of liquid crystal director reorientation was enhanced by frequency correlation analysis, to yield 2D FT-IR spectra. For the nematic liquid crystal 4-pentyl-4$\sp\prime$-cyanobiphenyl (5CB) the data suggest a different rate of response of the rigid and floppy parts of the LC molecules. The second application of dynamic step-scan FT-IR reported is the study of the response of various polymer films to sinusoidally modulated tensile strain. The main advantage of the technique is that it can provide valuable information at the molecular level that can be used to interpret the macroscopic properties of the polymeric material under investigation. Examples of application to different types of polymer films are presented. Results for several heterogeneous polymers including semicrystalline high density/low density polyethylene blends, the micro-phase separated copolymer Kraton$\sp\circler$ and a homogeneous polymer blend of polystyrene/polydimethylphenylene oxide are presented. Finally, the modification of a research-grade FT-IR spectrometer (Nicolet Instruments, System 800) for step-scan operation is described. Some applications of the instrument to photoacoustic spectroscopy (PAS) are presented.

scholarly journals Lens shape liquid crystals in electric fields

2021 ◽  
pp. 116085
Author(s):  
Zoltán Karaszi ◽  
Péter Salamon ◽  
Ágnes Buka ◽  
Antal Jákli
Keyword(s):  
Liquid Crystals ◽  
Electric Fields

Electro optical phenomena in lyotropic liquid crystals

1980 ◽  
Vol 28 (18) ◽  
pp. 608-612 ◽  
Author(s):  
D. Senatra ◽  
M. Vannini ◽  
A. P. Neri
Keyword(s):  
Liquid Crystals ◽  
Lyotropic Liquid Crystals ◽  
Optical Phenomena

Fabrication of ZrO 2 /rGO nanocomposites by flash sintering under AC electric fields

2021 ◽  
Author(s):  
Xinghua Su ◽  
Mengying Fu ◽  
Gai An ◽  
Zhihua Jiao ◽  
Qiang Tian ◽  
...  
Keyword(s):  
Electric Fields ◽  
Ac Electric Fields ◽  
Flash Sintering

Orientational elastic deformations in polymer liquid crystals induced by electric fields: Aromatic polyesters

1993 ◽  
Vol 29 (7) ◽  
pp. 1003-1012 ◽  
Author(s):  
V.N. Tsvetkov ◽  
N.V. Tsvetkov ◽  
L.N. Andreeva ◽  
A.Yu. Bilibin ◽  
S.S. Skorokhodov
Keyword(s):  
Liquid Crystals ◽  
Electric Fields ◽  
Elastic Deformations ◽  
Polymer Liquid ◽  
Polymer Liquid Crystals ◽  
Aromatic Polyesters

AC Electrokinetics for Biosensors

2004 ◽  
Author(s):  
M. Sigurdson ◽  
C. Meinhart ◽  
D. Wang
Keyword(s):  
Electric Fields ◽  
Dna Hybridization ◽  
Fluid Motion ◽  
Diffusive Transport ◽  
Analyte Concentration ◽  
Ac Electrokinetics ◽  
Ac Electric Fields ◽  
Binding Rate ◽  
Electrothermal Flow ◽  
Biosensor Device

We develop here tools for speeding up binding in a biosensor device through augmenting diffusive transport, applicable to immunoassays as well as DNA hybridization, and to a variety of formats, from microfluidic to microarray. AC electric fields generate the fluid motion through the well documented but unexploited phenomenon, Electrothermal Flow, where the circulating flow redirects or stirs the fluid, providing more binding opportunities between suspended and wall-immobilized molecules. Numerical simulations predict a factor of up to 8 increase in binding rate for an immunoassay under reasonable conditions. Preliminary experiments show qualitatively higher binding after 15 minutes. In certain applications, dielectrophoretic capture of passing molecules, when combined with electrothermal flow, can increase local analyte concentration and further enhance binding.

Reverse mode switching of the random laser emission in dye doped liquid crystals under homogeneous and inhomogeneous electric fields

2016 ◽  
Vol 4 (1) ◽  
pp. 7 ◽  
Author(s):  
M. Shasti ◽  
P. Coutino ◽  
S. Mukherjee ◽  
A. Varanytsia ◽  
T. Smith ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Electric Fields ◽  
Laser Emission ◽  
Mode Switching ◽  
Random Laser ◽  
Reverse Mode
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