Russian Scientists Explored the Structure of Nematic Liquid Crystal Materials
Together with colleagues, scientists from Immanuel Kant Baltic Federal University studied how capillary walls affect the flow of liquid crystals inside them: it turned out that before becoming uniform, the flow experiences the "tumbling" of molecules due to their interaction with the channel. Such systems are very sensitive to external influences and therefore can become the basis of high-precision sensors for various fields—from physics and printing to medicine and microbiology. The article based on this research is published in the Journal of Molecular Liquids.
Liquid-crystalline materials are viscous liquids whose molecules are arranged in a certain way. Being affected by an electric field, these elongated or disk-shaped shape particles are rearranging and starting to reflect light differently. This ability allows liquid crystals to be used as displays for various devices. However, their usefulness for humans is not limited by this. Due to the high sensitivity to external factors and simple design, the materials can be sensors, for example, in micro- and nanofluidics. These science areas study the behavior of very small fluid volumes, which also can be useful in microbiology, optics, and many other areas.
"Sensors located on liquid crystals are tiny devices made of branched capillaries. Being affected by the electric field, the material flows through these capillaries. Due to its sensitivity, it can change its properties even when interacting with the walls of the channel. It means that in order to develop the latest high-precision devices, these processes must be taken into account,"—says Pavel Maslennikov, one of the study authors, Ph.D. in Biology, associate professor at the Institute of Living Systems at Kant Baltic Federal University.
Together with colleagues from the Institute for Problems in Mechanical Engineering, Russian Academy of Sciences,(St. Petersburg, Russia), and Poznan University of Economics and Business (Poznan, Poland), scientists from Kant Baltic Federal University (Kaliningrad, Russia), studied how liquid crystal flows are formed in complex microscopic channels. An experimental study is very difficult because of some physical mechanisms, and therefore the authors used numerical simulation methods. The calculations showed that the capillary walls have a great influence on the future type of liquid crystal flow. Thus, the molecules of the material actively interact with the channel and when they move, they "somersault" first, which makes the flow turbulent, or vortex-like. After a while, the system stabilizes, and the contents of the capillary move smoothly and evenly—in a laminar flow.
"Numerical methods helped us to explore the role of confining surfaces in the type of the forming liquid crystal flow. This has great practical value because we can find answers to many questions even at the early design stage of new families of sensors and transmitters. For example, whether a given type of crystal is suitable as a material at all. The practical value of numerical simulation of complex processes occurring in micro- and nanoscale channels and capillaries is that these methods allow describing the possible scenario of development of the processes. Most of the time this cannot be done by experimental methods. Above all, the construction of such high-precision experimental facilities requires large financial expenses. All this making computational methods implemented within realistic molecular models more favorable compared to both purely analytical and experimental approaches,"—adds Alexander Zakharov, Ph.D. of Physical and Mathematical Sciences, Chief Researcher at the Institute for Problems in Mechanical Engineering of the Russian Academy of Sciences.
Provided by Immanuel Kant Baltic Federal University
