The law of hydrodynamics governing the way internally driven systems behave could explain their complex structure

October 29, 2012

Physicists use hydrodynamics to understand the physical mechanism responsible for changes in the long-range order of groups of particles. Particularly, Aparna Baskaran of Brandeis University, Massachusetts, USA, and Cristina Marchetti of Syracuse University, New York, USA, focused on ordered groups of elongated self-propelled particles. They studied the breakdown of long-range order due to fluctuations that render them unstable and give rise to complex structures, in a study about to be published in EPJ E.

The authors coined the term self-propelled nematics to refer to internally driven elongated that spontaneously align head to tail, like tinned sardines. These are characterised by an ordered state that is stationary on average. This means that there is a long-range order, i.e., the long axes of the molecules tend to align along a preferred direction, whereas the locally preferred direction may vary throughout the medium due to local strains or disturbances.

In this study, Baskaran and Marchetti first found that a uniform nematic state can be disturbed by density fluctuations associated with an upward current of active particles. Since the density in turn controls the onset of nematic order, this phenomenon is self-regulating and universal.

They also found that an instability can be triggered by a local distortion of particles' orientation. Such a distortion results in local currents that in turn amplify the distortion, leading to an instability deep inside the nematic state.

Future research will involve solving numerically the hydrodynamic equations to test the theory presented in this study and characterise the emergent structures. Ultimately, this work may help us gain a deeper understanding of and dynamics in a variety of internally driven systems, from epithelial cells and such as Myxococcus xanthus, to colloidal self-propelled nanorods.

Explore further: Nanorod-assembled order affects diffusion rate and direction

More information: European Physical Journal E 35:95, DOI 10.1140/epje/i2012-12095-8

Related Stories

Going Beyond Moore's Law by Using the Third Dimension

January 18, 2010

(PhysOrg.com) -- Scientists have demonstrated a new microwire fabrication technique in which microwires self-assemble themselves in a three-dimensional template made of nematic liquid crystals. Amidst concerns about Moore’s ...

Well-ordered nanorods could improve LED displays

October 25, 2012

Scientists have utilized the imaging capabilities of the Cornell High Energy Synchrotron Source (CHESS) to help develop enhanced light-emitting diode displays using bottom-up engineering methods.

'Cinderella' - biaxial liquid crystal - is found at last

February 12, 2010

Recent research at the DUBBLE beamline has proved the existence of liquid crystals with two main axes. Liquid crystals with a single main axis are already used in LCDs (liquid crystal displays), but crystals with two main ...

What do phasons look like?

June 6, 2012

(Phys.org) -- When illuminated by laser light, assorted colloidal particles can arrange themselves into highly ordered structures called quasicrystals. By changing the phases of the lasers, researchers can force the colloids ...

Cosmology in a Petri dish

January 26, 2012

Scientists have found that micron-size particles which are trapped at fluid interfaces exhibit a collective dynamic that is subject to seemingly unrelated governing laws. These laws show a smooth transitioning from long-ranged ...

Recommended for you

Electron highway inside crystal

December 8, 2016

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their ...

Researchers improve qubit lifetime for quantum computers

December 8, 2016

An international team of scientists has succeeded in making further improvements to the lifetime of superconducting quantum circuits. An important prerequisite for the realization of high-performance quantum computers is ...

A nano-roundabout for light

December 8, 2016

Just like in normal road traffic, crossings are indispensable in optical signal processing. In order to avoid collisions, a clear traffic rule is required. A new method has now been developed at TU Wien to provide such a ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.