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!

More articles from Materials Sciences:

nachricht Cementless fly ash binder makes concrete 'green'
19.06.2018 | Rice University

nachricht Ground-breaking discoveries could create superior alloys with many applications
19.06.2018 | Chalmers University of Technology

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

Im Focus: Photoexcited graphene puzzle solved

A boost for graphene-based light detectors

Light detection and control lies at the heart of many modern device applications, such as smartphone cameras. Using graphene as a light-sensitive material for...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

Latest News

Carbon nanotube optics provide optical-based quantum cryptography and quantum computing

19.06.2018 | Physics and Astronomy

How to track and trace a protein: Nanosensors monitor intracellular deliveries

19.06.2018 | Life Sciences

New material for splitting water

19.06.2018 | Physics and Astronomy

Science & Research
Overview of more VideoLinks >>>