Development of an Electrically Controllable Damper Using a Liquid Crystal

1996 ◽  
Vol 118 (3) ◽  
pp. 510-515 ◽  
Author(s):  
S. Morishita
Keyword(s):  
Liquid Crystal ◽  
Electric Field ◽  
Molecular Orientation ◽  
Nematic Phase ◽  
Organic Liquid ◽  
Working Fluid ◽  
Damping Force ◽  
Electric Voltage ◽  
Electroviscous Effect ◽  
Display Devices

This paper describes a new electrically controllable damper that uses a liquid crystal (LC) as the working fluid. LC is a homogeneous organic liquid characterized by the long-range order of its molecular orientation. The sample LC used in this work is a thermotropic, low molecular-weight LC which appears in the nematic phase, and was originally developed for display devices. The molecular orientation of the nematic phase is characterized by slender ellipsoidal shape molecules, the main axis of which can be controlled by applying an electric or magnetic field. When an electric field is applied to a LC, the orientation order of the molecules becomes parallel to the applied electric field, causing the apparent viscosity to increase. This phenomenon is known as the electroviscous effect. To study the application of the electroviscous effect of a LC to a controllable mechanical damping device, a prototype controllable damper was constructed and its performance was examined. In this damper, a piston, equipped with several concentric cylindrical electrodes attached to the piston rod, moves in the liquid crystal. During the reciprocal movement of the electrodes, LC flow through the electrodes is controlled by applying electric voltage to the latter. Damper performance was investigated under various DC electric field strengths, piston oscillation amplitudes and frequencies. The results show that the controllable damping force was three times larger with the application of an electric field than that without, and that the range of force variation was kept at the same level regardless of the frequency and amplitude of piston motion.

Thickness Control of Liquid Crystal Film in a Step Bearing by Electric Field Under Dynamic Loading Condition

Tribology ◽  
2005 ◽  
Author(s):  
Yoshiki Matsumura ◽  
Toshihiko Shiraishi ◽  
Shin Morishita
Keyword(s):  
Liquid Crystal ◽  
Electric Field ◽  
Pid Controller ◽  
Molecular Orientation ◽  
Organic Liquid ◽  
Orientational Order ◽  
Earthquake Excitation ◽  
Crystal Film ◽  
Dynamic Loading Condition ◽  
Viscosity Variation

This paper describes the viscosity variation of a liquid crystal under electric field, and its application to a controllable step bearing. Liquid crystal is known as a homogeneous organic liquid characterized by the long-range order of its molecular orientation. When an electric field is applied to a liquid crystal film as lubricant, the orientational order of molecules becomes parallel to the applied field, which causes apparent viscosity variation. In this paper, a controllable step bearing system was constructed and its dynamic characteristics were studied. When a step load, sinusoidal or earthquake excitation was applied to the bearing pad, the film thickness was successfully controlled to the appointed value by a conventional PID controller. The response frequency was also studied in the experiment.

Numerical Investigation of EDL Effects on the Flow Characters of Polar Fluids in Rectangular Microchannels

2006 ◽  
Author(s):  
Zhuo Li ◽  
Gui-Hua Tang ◽  
Ya-Ling He ◽  
Wen-Quan Tao
Keyword(s):  
Electrical Conductivity ◽  
Electric Field ◽  
Stokes Equations ◽  
Numerical Results ◽  
Ion Concentration ◽  
Working Fluid ◽  
Governing Equations ◽  
Rectangular Microchannels ◽  
Polar Fluids ◽  
Electroviscous Effect

Recently, a large number of experiments have been conducted to examine the applicability of Navier-Stokes equations to predict the friction factor for the laminar flow of polar fluids in microchannels. However, significant discrepancies still exist between various results. In order to investigate the effect of electric double layer on the pressure-driven flow of polar fluid in smooth rectangular microchannels and to reveal whether continuum model can still be applied, numerical investigations are conducted in this paper. The simulated microchannels are made of silicon engraved substrate with Pyrex cover, and the measured relative roughness of channels is less than 0.5%. Deionized water and tap water with different ion concentration and electrical conductivity are used as the working fluid. The governing equations include the two-dimensional, non-linear Poisson-Boltzmann equation, the modified N-S equation and the electric field Ez equation. The steady state electric field Ez equation is coupled with the momentum equation. The FVM (finite volume method) is adopted to discretize the governing equations. The non-uniform grid systems 152×102 is applied and the Reynolds number ranges from 0.1 to 300. Good agreements are achieved between the numerical results and the experimental data available in the literature. The effects of electrical potential, fluid ion concentration, electrical conductivity and the channel dimensions on the EDL profile, and the electroviscous effect and the friction coefficient are presented in detail. The simulation results reveal that the Debye thickness depends on ion concentration greatly. Only when the ratio of Dh/δ (the ratio of channel hydraulic diameter to the Debye thickness) is low, the electroviscous effect should be considered. According to the experimental conditions, the numerical results show that if the ratio of Dh/δ is greater than 15, the predicted friction factors agree well with the macroscale classical law, and the disparities are less than 4%.

ELECTRIC FIELD TUNING A SPECTRUM OF NEMATIC LIQUID CRYSTAL LASING WITH THE USE OF A PERIODIC SHADOW MASK

2007 ◽  
Vol 16 (01) ◽  
pp. 75-90 ◽  
Author(s):  
L. M. BLINOV ◽  
V. V. LAZAREV ◽  
S. P. PALTO ◽  
G. CIPPARRONE ◽  
A. MAZZULLA ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Electric Field ◽  
Plane Layer ◽  
Refraction Index ◽  
Transparent Electrode ◽  
Spatial Modulation ◽  
Shadow Mask ◽  
Electric Voltage ◽  
Resonance Modes ◽  
Resonator Structure

Lasing has been observed in the dye-doped isotropic and nematic phases of liquid crystals in a plane layer placed between one substrate with a uniform transparent electrode and another substrate with a system of parallel chromium (nontransparent) electrodes. The latter has a periodicity of 15 μm and plays a double role: (i) in both the phases it operates as a shadow mask providing a spatial modulation of the pump beam and consequently, a gain of the material and (ii) in the nematic phase it additionally creates a Bragg resonator structure with spatial modulation of the refraction index when an electric voltage is applied across the transparent and non-transparent electrodes. The resonator operates at high order Bragg resonance modes of numbers m = 71–79 for three lasing dyes studied. With that simple cell, a voltage induced tuning of the spectral positions of lasing lines over 25 nm has been demonstrated without using holographic or other complicated techniques. The mechanism of the observed phenomenon is discussed using modeling of the liquid crystal reorientation and optical properties in the spatially periodic electric field.

scholarly journals Ориентационный порядок в жидкокристаллических комплексах на основе лантаноидов

2018 ◽  
Vol 60 (4) ◽  
pp. 805
Author(s):  
Л.А. Добрун ◽  
А.П. Ковшик ◽  
Е.И. Рюмцев ◽  
А.А. Калинкин
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nematic Phase ◽  
Organic Liquid ◽  
Orientational Order ◽  
Complexing Agent ◽  
Temperature Range ◽  
First Time

AbstractIn this study, we have for the first time determined the degree of an orientational order S for a series of liquid-crystal complexes based on lanthanides (Eu^+3, Gd^+3, Tb^+3, Dy^+3) with the same ligand composition in the temperature range of existence of the nematic phase by using experimental refractometry results. We have also found an even-odd alternative S as number of protons in the ions complexing agent has consecutively increased. The obtained values of S have been compared with the corresponding degrees of order of the calamite organic liquid crystals.

Infrared Microscopic Imaging of the Diffusion of Liquid Crystals into Thermoplastics

1997 ◽  
Vol 3 (S2) ◽  
pp. 841-842
Author(s):  
Bentley G. Wall ◽  
Chris M. Snively ◽  
Jack L. Koenig
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Electric Field ◽  
Polymer Matrix ◽  
Thermoplastic Polymer ◽  
General Direction ◽  
Display Devices ◽  
Polymer Dispersed

Thermoplastic polymer/liquid crystal systems have found application in the generation of display devices known as thermoplastic, polymer dispersed liquid crystals (PDLCs). These systems take advantage of the beneficial properties of both components to generate a device that has unique optical properties. The liquid crystal is dielectric and responds to an electric field. The polymer confines the liquid crystal so that the cells are closed. The two components are melted together until they are miscible. At lower temperatures, the two components phase separate. The liquid crystal component is the minor phase and takes the form of many tiny droplets contained within the major-phase, polymer matrix. An application of an electric field across these systems causes the liquid crystal within the droplets to align with the field. The systems are engineered such that when this alignment occurs there is no refractive index difference between the liquid crystal in the droplets and the polymer matrix, thus, the cells appear optically transparent. When there is no field applied, the liquid crystals in each droplet are aligned without respect to a general direction according to the surface energetics of each droplet/polymer interface. When this is the case, there is a refractive index mismatch between the droplets and the polymer and the cells are opaque. Research of these systems is aimed at improving the optical properties in order to facilitate the manufacturing of improved devices utilizing this technology. Because these systems are generated by a diffusion-controlled, phase separation process, understanding the relevant parameters, particularly the diffusion coefficients, should enable the manufacturing processes of these systems to be controlled more efficiently, generating improved optical properties.

Mesomeric Effects of Azobenzene Bearing Natural Product Based Molecules for Liquid Crystal Materials: An Overview.

2020 ◽  
Vol 17 ◽  
Author(s):  
Saba Farooq ◽  
Zainab Ngaini
Keyword(s):  
Liquid Crystal ◽  
Natural Product ◽  
Nematic Phase ◽  
Optical Switching ◽  
Kojic Acid ◽  
Liquid Crystal Display ◽  
Smectic Phase ◽  
Active Materials ◽  
Smart Windows ◽  
Display Devices

: Latest progress in liquid crystal (LC) field related to azo molecules incorporated to natural product-based moieties for the improvement of LC texture and mesomeric phases has received great interest among researchers. LC containing natural product-based moieties i.e. menthol, kojic acid, cholesterol and chalcone with stable azo and azobenzene scaffolds with specific optical tunability has been widely reported for photo-active materials such as Liquid Crystal Display (LCD), LC films, smart windows and other devices. This review discusses on the influence of azobenzene, a renowned photo responsive and stable LC scaffold, in mesogenic phases due to photo-isomerization and optical switching. The incorporation of mesomeric phases natural product moieties to azo molecules has improved the properties of LC i.e from nematic phase to smectic phase with proper magnetic field alignment. Natural product-based LC can be useful in numerous applications especially practical electronic or optic devices i.e. optical image storage, display devices, solar cells, optical switching.

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