Featured Research

from universities, journals, and other organizations

Flowing structures in soft crystals

Date:
August 8, 2011
Source:
Vienna University of Technology, TU Vienna
Summary:
A liquid does not have to be a disordered bunch of particles. Researchers in Austria have discovered intriguing structures formed by tiny particles floating in liquids. Under mechanical strain, particle clusters in liquids can spontaneously form strings and dramatically alter the properties of the liquid.

Intriguing structures are formed by tiny particles floating in liquids.
Credit: Vienna University of Technology

A liquid does not have to be a disordered bunch of particles: A team of researchers at Vienna University of Technology (TU Vienna) and the University of Vienna has discovered intriguing structures formed by tiny particles floating in liquids. Under mechanical strain, particle clusters in liquids can spontaneously form strings and dramatically alter the properties of the liquid.

What is common to blood, ink and gruel? They are all liquids in which tiny particles are suspended -- so called "colloids." In some of these liquids, the particles form groups (clusters), which form regular structures, much like atoms in a crystal. A team of researchers from TU Vienna and Vienna University has now managed to study the remarkable properties of these crystal-like substances in computer simulations. Under mechanical strain, the crystalline pattern can change into a different structure, or it can vanish completely. The researchers anticipate a broad range of practical applications for these effects. The results of their calculations have now been published in the scientific journal Physical Review Letters.

Regular Structures in Liquids

If small particles accumulate, they can form clusters. Within a cluster, the particles may overlap and mingle, similar to a densely packed shoal of eels, gliding past each other. Remarkably, these clusters are not situated at random positions, but they spontaneously form a regular structure -- a "cluster crystal." The distance between two neighboring clusters is constant. "Increasing the density of particles adds more and more particles to each cluster -- but the distance between them stays the same," says Arash Nikoubashman, PhD-student at TU Vienna. He made the calculations together with Professor Gerhard Kahl (Institute for Theoretical Physics, TU Vienna) and Professor Christos Likos (University of Vienna).

Crystal Structure Turning into Strings

"Previous results had already led us to believe that these particles could exhibit strange behavior under certain external conditions," the physicists explain. And their hopes were not unfounded: in computer simulations they managed to calculate how the crystal-like structure behaves under mechanical strain that causes shears stress -- which means that surfaces within the liquid are shifted relative to each other. At first, the crystal structure starts to melt, the connections between the clusters are broken. From these molten particle clusters, a new regular order starts to emerge spontaneously. Long, straight strings of particle are formed, neatly aligned in parallel.

Thin and Thick

While these strings are created, the liquid gets thinner, its viscosity decreases. This is due to the strings being able to slide relative to one another. If the material is subject to even more strain, the strings break up too, a "molten" unstructured ensemble of particle clusters remains, and the viscosity of the liquid increases again. More and more particles are washed away from their original positions and inhibit the flow. This behavior is the same for all kinds of cluster crystals. With a simple theoretical model, the critical strain, at which the ordered structure vanishes completely, can be predicted very accurately.

Under shear strain, crystals made of soft, penetrable particles can exhibit new kinds of self-organization. Geometric structures emerge, governed by the kind of forces acting between the particles. This research in the field of "soft matter" in the micro- and nanometer regime is not only interesting from a theoretical point of view. These materials play an important role in our everyday life -- such as blood or large biopolymers like DNA. They are important in biotechnology, and also in petrochemistry and pharmacology -- wherever tailor-made nano materials are being used. A liquid which can change its viscosity under mechanical stress promises a broad spectrum of possible applications -- ranging from vibration dampers to protective clothing.


Story Source:

The above story is based on materials provided by Vienna University of Technology, TU Vienna. Note: Materials may be edited for content and length.


Journal Reference:

  1. Arash Nikoubashman, Gerhard Kahl, Christos Likos. Cluster Crystals under Shear. Physical Review Letters, 2011; 107 (6) DOI: 10.1103/PhysRevLett.107.068302

Cite This Page:

Vienna University of Technology, TU Vienna. "Flowing structures in soft crystals." ScienceDaily. ScienceDaily, 8 August 2011. <www.sciencedaily.com/releases/2011/08/110808083701.htm>.
Vienna University of Technology, TU Vienna. (2011, August 8). Flowing structures in soft crystals. ScienceDaily. Retrieved July 24, 2014 from www.sciencedaily.com/releases/2011/08/110808083701.htm
Vienna University of Technology, TU Vienna. "Flowing structures in soft crystals." ScienceDaily. www.sciencedaily.com/releases/2011/08/110808083701.htm (accessed July 24, 2014).

Share This




More Matter & Energy News

Thursday, July 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Robot Parking Valet Creates Stress-Free Travel

Robot Parking Valet Creates Stress-Free Travel

AP (July 23, 2014) 'Ray' the robotic parking valet at Dusseldorf Airport in Germany lets travelers to avoid the hassle of finding a parking spot before heading to the check-in desk. (July 23) Video provided by AP
Powered by NewsLook.com
Boeing Ups Outlook on 52% Profit Jump

Boeing Ups Outlook on 52% Profit Jump

Reuters - Business Video Online (July 23, 2014) Commercial aircraft deliveries rose seven percent at Boeing, prompting the aerospace company to boost full-year profit guidance- though quarterly revenues missed analyst estimates. Bobbi Rebell reports. Video provided by Reuters
Powered by NewsLook.com
Europe's Car Market on the Rebound?

Europe's Car Market on the Rebound?

Reuters - Business Video Online (July 23, 2014) Daimler kicks off a round of second-quarter earnings results from Europe's top carmakers with a healthy set of numbers - prompting hopes that stronger sales in Europe will counter weakness in emerging markets. Hayley Platt reports. Video provided by Reuters
Powered by NewsLook.com
9/11 Commission Members Warn of Terror "fatigue" Among American Public

9/11 Commission Members Warn of Terror "fatigue" Among American Public

Reuters - US Online Video (July 22, 2014) Ten years after releasing its initial report, members of the 9/11 Commission warn of the "waning sense of urgency" in combating terrorists attacks. Mana Rabiee reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins