Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Scientists found and studied complex types of defects in the droplets of liquid crystals


A team of scientists from Kirensky Institute of Physics of the Siberian Branch of Russian Academy of Science and Siberian Federal University (SFU) together with Russian and foreign colleagues studied the droplets of a cholesteric liquid crystal that contained a twisted defect loop. The results of the study were published in Scientific Reports journal.

Liquid crystals (LCs) are chemical substances that enter mesophase (the state between solid matter and liquid) within a certain range of temperatures. Liquid crystals combine two opposite properties: they have fluidity which is typical for liquids and anisotropy of physical properties (i.e. difference in properties depending on direction) which is characteristic of solid crystals.

Droplets of a cholesteric liquid crystal as viewed through a polarizing microscope.

Courtesy of Mikhail Krakhalev

These peculiarities are explained by orientational order of long molecular axes. As a result of this the molecules an LC consists of remain relatively mobile on the one hand, but on the other hand are oriented in a certain way determining anisotropy of properties. Molecules may have different orientation, and moreover, it may change under the influence of an electric field. That is why LCs are widely used in electrical optic devices, such as display screens.

The team worked with liquid crystals that are called cholesterics or chiral nematics. Each molecule of a liquid crystal has several rotation axes. In orientation structures a predominant direction of long molecular axes is called a director. In case of cholesterics the director forms a twisted helical structure. It means that the directions of long molecular axes (and therefore their dipole moment) are turned against each other at a certain angle, and their ends trace out a spiral line (a helix) around the axis of the helicoid.

The peculiar orientation of LC molecules leads to spatial modulation of a cholesteric's refraction index, i.e. it changes harmonically. The light moving through such a structure diffracts. The feature of light propagation through a cholesteric LC is determined by the parameters of the helical orientation structure that depend on the properties of the liquid crystal and the nature of its interaction with the environment.

The scientists studied the structure of a cholesteric LC in droplets that were tens of microns in size and had perpendicular directors at the boundary with polymer. It turned out, that the helical structure in various parts of droplets had different helix pitch, i.e. the distances at which the director made a complete turn.

"We've studied the structure formed in the droplets of a cholesteric LC in detail, and showed how the droplets look at different aspect directions and droplet sizes using an optical microscope. We've also studied the influence of an electric field on the periodicity structure and the shape of linear defect," said Mikhail Krakhalev, a co-author of the work, a candidate of physical and mathematical sciences, senior scientific associate of Kirensky Institute of Physics, and the dean of the Chair of General Physics at the Institute of Engineering Physics and Radio Electronics, SFU.

The scientists proved that a defect shaped as a twisted double helix is formed in cholesteric droplets. The authors also studied the optic textures of such structures that could be observed in an optical microscope. Given that the structures formed in cholesteric droplets are quite complex, respective optic textures are determined by a bigger number of factors.

"We've studied and described the correlation between the optical texture of the droplets and their size and the aspect directions. The described structures may help identify similar configurations in other systems, and the approach suggested by us may be used to analyze complex orientation structures," concluded Mikhail Krakhalev.


The work was a collaboration of scientists representing Kirensky Institute of Physics of the Siberian Branch of Russian Academy of Science, Lomonosov Moscow State University, and National Cheng Kung University (Taiwan).

Media Contact

Yaroslava Zhigalova


Yaroslava Zhigalova | EurekAlert!

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

Latest News

Scientists re-create brain neurons to study obesity and personalize treatment

20.04.2018 | Health and Medicine

Spider silk key to new bone-fixing composite

20.04.2018 | Materials Sciences

Clear as mud: Desiccation cracks help reveal the shape of water on Mars

20.04.2018 | Earth Sciences

Science & Research
Overview of more VideoLinks >>>