Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Liquid-crystal and bacterial living materials self-organize and move in their own way

12.05.2017

Smart glass, transitional lenses and mood rings are not the only things made of liquid crystals; mucus, slug slime and cell membranes also contain them. Now, a team of researchers is trying to better understand how liquid crystals, combined with bacteria, form living materials and how the two interact to organize and move.

"One of the ideas we came up with was materials that live," said Igor S. Aronson, holder of the Huck Chair and Professor of Biomedical Engineering, Chemistry and Mathematics. Living matter, active matter may be self-healing and shape-changing and will convert energy to mechanical motion."


Computer generated model on the top left shows the pattern created by the interaction of bacteria and a nematic liquid crystal. Areas form that concentrate bacteria while others funnel bacteria away creating an absence of bacteria. The image on the right shows the concentration difference of bacteria as the liquid crystal patterns change. Bottom left image shows the changing velocity of the bacteria and the bottom right image shows the changes in concentration of the bacteria. The more bacteria in an area, the faster they move. (Video)

Credit: Aronson's Lab, Penn State

The living material Aronson is exploring using predictive computational models and experiments is composed of a bacterium -- Bacillus subtilis -- that can move quickly using its long flagella and a nematic liquid crystal -- disodium cromoglycate.

Liquid crystals as materials sit somewhere between a liquid and a solid. In this case, the molecules in disodium cromoglycate line up in long parallel rows, but are not fixed in place. Capable of moving, they remain oriented in only one direction unless disturbed.

According to Aronson, this type of liquid crystal closely resembles a straight-plowed field with the ridges the molecules and the furrows the areas in between.

Previously the researchers found that these tiny bacteria in a liquid crystal material can push cargo -- tiny particles -- through the channels in a liquid crystal and move at four times their body length when in small concentrations, but conservatively, at 20 times their body length when in large numbers.

"An emergent property of the combination of a liquid crystal and bacteria is that at about a 0.1 percent-by-volume bacterial concentration we start to see a collective response from the bacteria," said Aronson.

This type of living material is not simply a combination of two components, but the two parts create something with unusual optical, physical or electrical properties. However, there is no direct connection between the bacteria and the liquid. The researchers' computer models showed collective behavior in their system similar to that seen in actual liquid crystal/bacteria combinations.

The predictive computational models for this liquid-crystal bacteria system show a change from straight parallel channels when only a small bacteria population exists, to a more complex, organized, active configuration when bacteria populations are higher. While the patterns are always changing, they tend to form pointer defects -- arrow shapes -- that serve as traps and concentrate bacteria in an area, and triangle defects that direct bacteria away from the area.

Increased bacterial concentration increases the velocity of the bacteria and configurations in areas with higher bacteria population change more rapidly than in areas with fewer bacteria. Aronson and his team looked at actual liquid-crystal living materials in a slightly different way than in the past. They wanted the liquid-crystal thin film to be independent, not touching any surface, so they used a device that created the film -- in a way similar to that used to create large soap bubbles -- and suspended it away from surface contact. This approach showed patterns of defects in the material's structure.

Experiments with thin films of liquid crystals and bacteria produced the same results as the computational models, according to the researchers.

Another effect the researchers found was that when oxygen was removed from the system, the action of the living material stopped. Bacillus subtilis is usually found in places with oxygen, but can survive in environments devoid of oxygen. The bacteria in the living material did not die, they simply stopped moving until oxygen was once again present.

The researchers reported in Physical Review X that their "findings suggest novel approaches for trapping and transport of bacteria and synthetic swimmers in anisotropic liquids and extend a scope of tools to control and manipulate microscopic objects in active matter." Because some biological substances like mucus and cell membranes are sometimes liquid crystals, this research may produce knowledge of how these biological substances interact with bacteria and might provide insight on diseases due to bacterial penetration in mucus.

###

Also working on this project were Mikhail M. Genkin, doctoral student in engineering science and applied mathematics, Northwestern University; Andrey Sokolov, materials scientist, Argonne National Laboratory; and Oleg D. Lavrentovich, Trustees Research Professor, Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University.

The U.S. Department of Energy supported this work.

Media Contact

A'ndrea Elyse Messer
aem1@psu.edu
814-865-9481

 @penn_state

http://live.psu.edu 

A'ndrea Elyse Messer | 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: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Global study of world's beaches shows threat to protected areas

19.07.2018 | Earth Sciences

New creepy, crawly search and rescue robot developed at Ben-Gurion U

19.07.2018 | Power and Electrical Engineering

Metal too 'gummy' to cut? Draw on it with a Sharpie or glue stick, science says

19.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>