Structuralization of magnetic nanoparticles in 5CB liquid crystals

Soft Matter ◽  
2017 ◽  
Vol 13 (43) ◽  
pp. 7890-7896 ◽  
Author(s):  
Veronika Gdovinová ◽  
Martin A. Schroer ◽  
Natália Tomašovičová ◽  
Ingo Appel ◽  
Silke Behrens ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Magnetic Nanoparticles ◽  
Composite Systems

This work is devoted to the study of highly stable composite systems of the liquid crystal 4-n-pentyl-4′-cyanobiphenyl (5CB) doped with CoFe2O4 magnetic nanoparticles.

scholarly journals Study of Structural Changes in Nematic Liquid Crystals Doped with Magnetic Nanoparticles Using Surface Acoustic Waves

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1023
Author(s):  
Peter Bury ◽  
Marek Veveričík ◽  
František Černobila ◽  
Peter Kopčanský ◽  
Milan Timko ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Magnetic Nanoparticles ◽  
Electric Fields ◽  
Acoustic Waves ◽  
Structural Changes ◽  
Surface Acoustic Waves ◽  
Theoretical Background ◽  
Isotropic Phase ◽  
Structure Of Nanoparticles

The surface acoustic waves (SAWs) were used to study the effect of magnetic nanoparticles on nematic liquid crystal (NLC) behavior in weak magnetic and electric fields. The measurement of the attenuation of SAW propagating along the interface between piezoelectric substrate and liquid crystal is showed as an effective tool to study processes of structural changes. The magnetic nanoparticles Fe3O4 of nanorod shape and different low volume concentration were added to the NLC (4-(trans-4′-n-hexylcyclohexyl)-isothiocyanatobenzene (6CHBT)) during its isotropic phase. In contrast to undoped liquid crystals the distinctive different SAW attenuation responses induced by both magnetic and also electric fields in studied NLC samples were observed suggesting both structural changes and the orientational coupling between both magnetic and electric moments of nanoparticles and the director of the NLC molecules. Experimental measurements including the investigation under linearly increasing and/or jumped magnetic and electrical fields, respectively, as well as the investigation of temperature and time influences on structural changes were done. The investigation of the SAW anisotropy gives supplemental information about the internal structure of nanoparticles in investigated NLCs. In addition, some magneto-optical investigations were performed to support SAW results and study their stability and switching time. The analysis of observed SAW attenuation characteristics confirmed the role of concentration of magnetic nanoparticles on the resultant behavior of investigated NLC compounds. Obtained results are discussed within the context of previous ones. The theoretical background of the presented SAW investigation is introduced, too.

scholarly journals Steady-state rheology and structure of soft hybrid mixtures of liquid crystals and magnetic nanoparticles

Soft Matter ◽  
2020 ◽  
Vol 16 (10) ◽  
pp. 2516-2527
Author(s):  
Gaurav P. Shrivastav ◽  
Nima H. Siboni ◽  
Sabine H. L. Klapp
Keyword(s):  
Liquid Crystal ◽  
Steady State ◽  
Liquid Crystals ◽  
Magnetic Nanoparticles ◽  
Magnetic Nanoparticle ◽  
Dipolar Coupling ◽  
Hybrid Mixtures

The rhology of liquid crystal–magnetic nanoparticle mixtures is strongly dependent on the strength of the dipolar coupling among the magnetic nanoparticles.

Doping of nematic cyanobiphenyl liquid crystals with mesogen-hybridized magnetic nanoparticles

2017 ◽  
Vol 19 (19) ◽  
pp. 12127-12135 ◽  
Author(s):  
Ingo Appel ◽  
Hajnalka Nádasi ◽  
Christian Reitz ◽  
Nerea Sebastián ◽  
Horst Hahn ◽  
...  
Keyword(s):  
Optical Properties ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Magnetic Nanoparticles ◽  
Magnetic Nanoparticle ◽  
Surface Engineering

Surface engineering of magnetic nanoparticles with (pro-)mesogenic ligands leads to colloidally stable magnetic nanoparticle–liquid crystal hybrids with interesting magneto-optical properties.

New structure induced by elastic anisotropy in cylindrical nematic liquid crystal

2017 ◽  
Vol 13 (2) ◽  
pp. 4705-4717
Author(s):  
Zhang Qian ◽  
Zhou Xuan ◽  
Zhang Zhidong
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nematic Liquid Crystal ◽  
Elastic Anisotropy ◽  
Nematic Liquid Crystals ◽  
Gennes Theory

Basing on Landau–de Gennes theory, this study investigated the chiral configurations of nematic liquid crystals confined to cylindrical capillaries with homeotropic anchoring on the cylinder walls. When the elastic anisotropy (L2/L1) is large enough, a new structure results from the convergence of two opposite escape directions of the heterochiral twist and escape radial (TER) configurations. The new defect presents when L2/L1≥7 and disappears when L2/L1<7. The new structure possesses a heterochiral hyperbolic defect at the center and two homochiral radial defects on both sides. The two radial defects show different chiralities.

scholarly journals Liquid Crystal Devices for Beam Steering Applications

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 247
Author(s):  
Rowan Morris ◽  
Cliff Jones ◽  
Mamatha Nagaraj
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Adaptive Optics ◽  
Beam Steering ◽  
Optical Components ◽  
Advantages And Disadvantages ◽  
Liquid Crystal Devices

Liquid crystals are valuable materials for applications in beam steering devices. In this paper, an overview of the use of liquid crystals in the field of adaptive optics specifically for beam steering and lensing devices is presented. The paper introduces the properties of liquid crystals that have made them useful in this field followed by a more detailed discussion of specific liquid crystal devices that act as switchable optical components of refractive and diffractive types. The relative advantages and disadvantages of the different devices and techniques are summarised.

scholarly journals Optical Response Associated with the Orientation and Structure of Liquid Crystals with Respect to Phosphatidylcholine Concentration

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 678
Author(s):  
Yuqi Han ◽  
Yan Jiang ◽  
Wei Guo ◽  
Bing Li ◽  
Lu Zhang ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Reflectance Spectrum ◽  
Optical Response ◽  
The Self ◽  
Cholesteric Liquid Crystals ◽  
Anchoring Effect ◽  
Self Assembling ◽  
Sensitization Effect ◽  
Structure Of Liquid

Based on the anchoring effect due to the self-assembling behavior of the phospholipid molecules at the interface between the liquid crystal and water phases on the orientation of liquid crystals, the optical response associated with the orientation and structure of liquid crystals with respect to the concentration of 1,2-didodecanoyl-sn-glycero-3-phosphocholine solution has been investigated. The optical response owing to changes in the orientation and structure of the mixed cholesteric liquid crystals with respect to the change in the concentration of phosphatidylcholine has been obtained. Moreover, the feasibility of using as-prepared mixed cholesteric liquid crystals to measure the phosphatidylcholine concentration has been verified. A methodology to measure the reflectance spectrum by using mixed cholesteric liquid crystals to sensitize the phosphatidylcholine concentration has been further realized. The sensitization effect of the mixed cholesteric liquid crystals on the measurement of phosphatidylcholine concentration was also verified.

scholarly journals Optofluidic Platform Based on Liquid Crystals in X-Cut Lithium Niobate: Thresholdless All-Optical Response

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 908
Author(s):  
Fabrizio Ciciulla ◽  
Annamaria Zaltron ◽  
Riccardo Zamboni ◽  
Cinzia Sada ◽  
Francesco Simoni ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Light Intensity ◽  
Lithium Niobate ◽  
Photovoltaic Effect ◽  
Optical Control ◽  
Crystal Layer ◽  
Liquid Crystal Layer ◽  
Threshold Behaviour ◽  
All Optical

In this study, we present a new configuration of the recently reported optofluidic platform exploiting liquid crystals reorientation in lithium niobate channels. In order to avoid the threshold behaviour observed in the optical control of the device, we propose microchannels realized in a x-cut crystal closed by a z-cut crystal on the top. In this way, the light-induced photovoltaic field is not uniform inside the liquid crystal layer and therefore the conditions for a thresholdless reorientation are realized. We performed simulations of the photovoltaic effect based on the well assessed model for Lithium Niobate, showing that not uniform orientation and value of the field should be expected inside the microchannel. In agreement with the re-orientational properties of nematic liquid crystals, experimental data confirm the expected thresholdless behaviour. The observed liquid crystal response exhibits two different regimes and the response time shows an unusual dependence on light intensity, both features indicating the presence of additional photo-induced fields appearing above a light intensity of 107 W/m2.

scholarly journals Color Response Modification of Encapsulated Liquid Crystals Used in Rotating Disk Heat Transfer Studies

1995 ◽  
Author(s):  
Cengiz Camci ◽  
Boris Glezer
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Rotational Speed ◽  
Rotating Disk ◽  
Point Of View ◽  
Centrifugal Acceleration ◽  
Relative Shift ◽  
Color Response ◽  
Stationary Conditions

The liquid crystal thermography can be successfully used in both transient and steady-state heat transfer experiments with excellent spatial resolution and good accuracy. Although most of the past liquid crystal based heat transfer studies are reported in the stationary frame, measurements from the rotating frame of turbomachinery systems exist The main objective of the present investigation is to determine the influence of rotation on the color calibration of encapsulated liquid crystals sprayed on the flat surface of a rotating aluminum disk. The investigation is performed for a rotational speed range from 0 rpm to 7500 rpm using three different liquid crystal coatings displaying red at 30, 35 and 45° C, under stationary conditions. An immediate observation from the present study is that the color response of liquid crystals is strongly modified by the centrifugal acceleration of the rotating environment. It is consistently and repeatedly observed that the hue versus temperature curve is continuously shifted toward lower temperatures by increasing rotational speed. The relative shift of the display temperature of the green can be as high as 7°C at 7500 rpm when compared to the temperature of the green observed under stationary conditions. The present study shows that relative shift of the liquid crystal color has a well-defined functional dependency to rotational speed. The shift is linearly proportional to the centrifugal acceleration. It is interesting to note that the individual shift curves of the green for all three liquid crystal coatings collapse into a single curve when they are normalized with respect to their own stationary green values. When the color attribute is selected as “intensity” instead of “hue”, very similar shifts of the temperature corresponding to the intensity maximum value appearing around green is observed. An interpretation of the observed color shift is made from a thermodynamics energy balance point of view.

Line broadening in the electron resonance spectra of spin probes dissolved in anisotropic media: the effect of nuclear spin quantization

1977 ◽  
Vol 353 (1672) ◽  
pp. 87-102 ◽  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Nuclear Spin ◽  
Dynamic Properties ◽  
Orientational Order ◽  
Anisotropic Media ◽  
Approximate Theory ◽  
Spin Probes ◽  
Line Broadening ◽  
Electron Resonance

The line broadening in the electron resonance spectra of monoradicals dissolved in anisotropic media, such as liquid crystals, provides a valuable probe of both the orientational order and the molecular dynamics. However, the fast-motion relaxation theory employed to extract this information from the linewidths assumes that the nuclear spin is quantized along the direction of the magnetic field. This approximation is only correct when the symmetry axis of a uniaxial liquid crystal is either parallel or perpendicular to the field. We have therefore removed this assumption and have developed a general theory of line broadening valid for all orientations of the liquid crystal. The theory is then used to evaluate the angular dependence of the linewidths and this is compared with the dependence predicted by the approximate theory, for two classes of nitroxide spin probes. These comparisons reveal that for steroidal spin probes the error, introduced by assuming the nuclear spin to be quantized along the field, is confined to the dynamic properties derived from the linewidths. In contrast, significant errors appear in both the dynamic and static properties obtained from an analysis of the linewidth variations for fatty acid spin probes based on the approximate theory. It would seem that the exact theory must be employed to obtain precise information from linewidth investigations of liquid crystals, except when the orientational order is extremely small.

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