Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

When repulsive particles stick together – A new angle on clustering

14.03.2006


Even when they mutually repel each other, material particles in a solution can still form clusters. Details on the conditions necessary for this seemingly contradictory, phenomenon have now been published, following a project supported by the Austrian Science Fund FWF. Though they come from the realm of theoretical physics these findings may be very important for understanding of the ordering of polymer-like entities — and increase the standing of the fledgling field of soft matter physics in Austria.



Milk and mayonnaise, paints and inks, proteins and DNA are all examples of what is known as "soft matter". It is only recently that their physical characteristics have been systematically investigated, often with surprising outcomes. One such result has now been published by a group led by Prof. Gerhard Kahl of the Institute of Theoretical Physics at the Vienna University of Technology.

Hard Facts on Soft Matter


"Intuitively, you would only expect particles in a fluid to aggregate when they attract each other," explained Prof. Kahl, "but we have been able to show that this needn’t always be the case. Even particles that completely repel each other can form clusters." The conditions necessary for this can be created by a particular type of soft matter, known as colloidal dispersions. In such systems, relatively large particles (e.g. polymers) are dissolved in a solvent made up of far smaller particles.

Together with colleagues at the Universities of Vienna and Düsseldorf, the team has now carried out computations on these types of solutions and has clearly shown that particles which repel each other can still aggregate, provided that two conditions are met. Firstly, the particles must be able to overlap each other and, secondly, increasing the distance between them must lead to a rapid reduction in the strength of the repulsion.

If these conditions are fulfilled, then the seemingly contradictory behaviour of the particles can be observed. Mag. Bianca Mladek and Dr. Dieter Gottwald, both members of Prof. Kahl’s team, have used complex computer simulations to confirm their surprising predictions. The strong agreement between the theoretical results and computer simulations convinced the referees, leading to publication in the prestigious Physical Review Letters journal.

Crystals under Pressure

The behaviour of particles when subjected to pressure yielded further unexpected results. Prof. Kahl commented: "Under high pressure, the clusters arrange themselves into crystals. We were even more surprised with the findings of further investigations which showed that the spacing between the ordered crystalline clusters remains constant when compressed further — a characteristic which is made possible by the aggregation of more and more particles in the clusters." These findings contrast with the behaviour of other ordered systems, such as ordinary crystalline metals, where the lattice spacings decrease under pressure.

Due to the high complexity of colloidal dispersions, such computations require certain mathematical tricks. Outlining the methodology, Prof. Kahl explained: "Statistical mechanics is the fundamental theory to describe soft matter behaviour. However, the large number of degrees of freedom of the larger particles in the dispersions posed a formidable computational problem. Through appropriate averaging we were able to dramatically reduce the number of degrees of freedom, so that the behaviour of the particles would only depend on a small number of coordinates."

Prof. Kahl believes that the findings, some of which are highly unexpected, show that nature offers a wide variety of solutions for the optimal energetic ordering of particles, many of which are still unknown. The FWF project will not only contribute towards unlocking some of these secrets, but will also help put the new field of soft matter research on a firm footing in Austria.

Till C. Jelitto | alfa
Further information:
http://www.fwf.ac.at/en/press/pv200603-en.html

More articles from Physics and Astronomy:

nachricht New type of low-energy nanolaser that shines in all directions
18.12.2018 | Eindhoven University of Technology

nachricht NASA research reveals Saturn is losing its rings at 'worst-case-scenario' rate
18.12.2018 | NASA/Goddard Space Flight Center

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

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

Im Focus: Data storage using individual molecules

Researchers from the University of Basel have reported a new method that allows the physical state of just a few atoms or molecules within a network to be controlled. It is based on the spontaneous self-organization of molecules into extensive networks with pores about one nanometer in size. In the journal ‘small’, the physicists reported on their investigations, which could be of particular importance for the development of new storage devices.

Around the world, researchers are attempting to shrink data storage devices to achieve as large a storage capacity in as small a space as possible. In almost...

Im Focus: Data use draining your battery? Tiny device to speed up memory while also saving power

The more objects we make "smart," from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.

Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved...

Im Focus: An energy-efficient way to stay warm: Sew high-tech heating patches to your clothes

Personal patches could reduce energy waste in buildings, Rutgers-led study says

What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...

Im Focus: Lethal combination: Drug cocktail turns off the juice to cancer cells

A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.

The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...

Im Focus: New Foldable Drone Flies through Narrow Holes in Rescue Missions

A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.

Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

ICTM Conference 2019: Digitization emerges as an engineering trend for turbomachinery construction

12.12.2018 | Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

 
Latest News

Pressure tuned magnetism paves the way for novel electronic devices

18.12.2018 | Materials Sciences

New type of low-energy nanolaser that shines in all directions

18.12.2018 | Physics and Astronomy

NASA research reveals Saturn is losing its rings at 'worst-case-scenario' rate

18.12.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>