Related Experiment Video
Updated: Jul 30, 2025
06:24
High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal
Published on: October 31, 2019
6.5K
Twist-bend nematic drops as colloidal particles: Electric instabilities.
K S Krishnamurthy1, D S Shankar Rao1, Santosh Y Khatavi1
1Centre for Nano and Soft Matter Sciences, Survey No. 7, Shivanapura, Bangalore 562162, India.
Physical Review. E
|May 18, 2023
Summary
This study explores the behavior of twist-bend nematic (N_{TB}) drops in an electric field, revealing flexoelectric and electrokinetic responses. These drops exhibit unique movements and alignments, offering insights into liquid crystal dynamics.
Area of Science:
- Liquid Crystal Physics
- Soft Matter Science
- Materials Science
Background:
- The study investigates the mesogen 1,''7''-bis(4-cyanobiphenyl-4'-yl)heptane (CB7CB) doped with an amphiphilic compound.
- Focuses on the biphasic state where twist-bend nematic (N_{TB}) drops are dispersed in an isotropic fluid.
Purpose of the Study:
- To examine the flexoelectric and electrokinetic responses of N_{TB} drops in various geometries (escaped-radial-like and parabolic focal conic defects).
- To understand the influence of low-frequency electric fields on N_{TB} drop behavior, including dimensional changes and core relocations.
- To elucidate the electrohydrodynamic effects and hydrodynamic flows within N_{TB} drops under varying electric field conditions.
Main Methods:
- Experimental observation of N_{TB} drops under applied low-frequency electric fields.
- Analysis of drop geometry, defect structures (confocal parabolas, hedgehog core), and alignment.
- Characterization of translatory motion and vortical flows using principles like the Taylor-Melcher leaky dielectric model.
Main Results:
- Periodic dimensional changes in drops with parabolic focal conic defects contribute to flexoelectric free-energy reduction.
- In escaped-radial-like (ER) droplets, flexoelectric effects are achieved through hedgehog core relocations.
- ER drops exhibit field-dependent translatory motion (velocity quadratic in field strength) over a broad frequency range (dc to MHz), with direction reversal at a critical frequency.
- Patterned states and homeotropic alignment are observed at different field strengths and voltage crossings.
- Vortical flows become discernible in ER drops at high electric fields.
Conclusions:
- N_{TB} drops display complex flexoelectric and electrokinetic behaviors in response to electric fields.
- The geometry of the drops, particularly off-centered configurations, plays a crucial role in enabling electrohydrodynamic effects.
- The study provides a detailed understanding of the dynamic responses of N_{TB} drops, relevant for liquid crystal display and microfluidic applications.
Related Concept Videos
01:09Colloidal precipitates
634
The high insolubility of some precipitates can result in an unfavorable relative supersaturation. This can lead to colloidal particles with a large surface-to-mass ratio, where adsorption is promoted. For instance, in the precipitation of silver chloride, silver ions are adsorbed on the surface of the colloidal particles, forming a primary layer. This layer attracts ions of opposite charge (such as nitrate ions), forming a diffuse secondary layer of adsorbed ions. This electric double layer...
634
03:22Colloids
17.6K
Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles that are visible to the naked eye or can be seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. On the other hand, a solution is a homogeneous mixture in which no settling occurs and in which the dissolved...
17.6K
01:17Colloids and Suspensions
1.9K
Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles visible to the naked eye or seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. The suspended particles in a suspension settle out after some time of mixing. The separation of particles from a suspension is...
1.9K
01:28Induced Electric Dipoles
4.3K
A permanent electric dipole orients itself along an external electric field. This rotation can be quantified by defining the potential energy because the external torque does work in rotating it. Then, the potential energy is minimum at the parallel configuration and maximum at the antiparallel configuration. While the former is a stable equilibrium, the latter is an unstable equilibrium.
Since the absolute value of potential energy holds no physical meaning, its zero value can be chosen as per...
Since the absolute value of potential energy holds no physical meaning, its zero value can be chosen as per...
4.3K
01:23Atomic Nuclei: Nuclear Relaxation Processes
690
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis.
690
01:29Potential Due to a Polarized Object
443
A neutral atom consists of a positively charged nucleus surrounded by a negatively charged electron cloud. When placed in an external electric field, the external electric force pulls the electrons and nucleus apart, opposite to the intrinsic attraction between the nucleus and the electrons. The opposing forces balance each other with a slight shift between the center of masses of the nucleus and the electron cloud, resulting in a polarized atom. On the other hand, a few molecules, like water,...
443