Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Of traffic jams, beach sands and the zero-temperature jamming transition

Researchers in condensed matter physics at the University of Pennsylvania and the University of Chicago have created an experimental and computer model to study how jamming, the physical process in which collections of particles are crammed together to behave as solids, might affect the behavior of systems in which thermal motion is important, such as molecules in a glass.

The study presents the first experimental evidence of a vestige of the zero temperature jamming transition — the density at which large, loose objects such as gas bubbles in liquid, grains of sand or cars become rigid solids such as foam, sand dunes or traffic jams — in a system of small particles where thermal energy is important.

This demonstrates that despite the fact that the size of constituent particles differ by many orders of magnitude, molecules in a glass retain an echo of the phenomenon of how boulders coming to rest to form a solid rock pile.

"We have been testing the speculation that jamming has a common origin in these different systems," Andrea Liu, an author of the study and professor in the Department of Physics at Penn, said.

The paper appears in the current issue of the journal Nature.

The idea of jamming is that slow relaxations in many different systems, ranging from glass-forming liquids to suspensions of particles such as bits of ice in a milkshake to foams and granular materials, can be viewed in a common framework. For example, one can define jamming to occur when a system develops a yield stress or extremely long stress relaxation time in a disordered state. Foams and granular materials flow when a large shear stress is applied but jam when the shear stress is lowered below the yield stress. But systems of large particles such as foams and granular materials can be considered zero-temperature systems because the energy associated with a typical temperature, such as room temperature, is negligible compared to the energy required to shift the particles. As a result, it is not known whether the jamming of such systems is related to the jamming of systems of small particles, such as molecular liquids, which jam as temperature is lowered through the glass transition.

The Penn study involved mathematical computer simulations and an experiment to touch on this very general problem. The analysis focuses on an intuitive feature of the system, the separation between neighboring spheres, and, in particular, on how this separation evolves as the system becomes jammed. By confining soft microspheres that swell and shrink by changing the temperature of the system and that are small enough so that thermal motion is important, researchers were able to study how the separation distance evolves as the volume occupied by the spheres is varied through the jamming transition. The experiments discovered a vestige, at non-zero temperature, of one of the important structural signatures to arise at the zero-temperature jamming transition.

The computer simulations and experiments provide new clues about the connections between jamming and the glass transition and provide a concrete experimental route to explore them.

"Most people have experienced jamming and unjamming in one way or another, by sitting in a traffic jam or tapping a container of flour to get the powder to flow," said. "But we also use jamming to make the strongest metallic alloys and toughest plastics. Elucidation of the principles of jamming, therefore, holds potential to be of practical importance and will most certainly be of interest to anyone who has wondered why honey ceases to flow when it is cooled in a refrigerator or why earth or snow can suddenly form avalanches with catastrophic results."

The study was funded by the Department of Energy and by the National Science Foundation, which supports the Materials Research Science and Engineering Centers at Penn and the University of Chicago. The research team also acknowledges the support of the Teraport computer cluster at Chicago.

The study was conducted by Liu, Zexin Zhang, Daniel T. N. Chen, Ahmed M. Alsayed, Peter Yunker and Arjun G. Yodh of the Department of Physics and Astronomy in Penn's School of Arts and Sciences; Ning Xu, of Penn and the James Franck Institute at Chicago; Sidney R. Nagel of the James Franck Institute; Kevin B. Aptowicz of the Department of Physics at West Chester University; and Piotr Habdas of the Department of Physics at Saint Joseph's University.

Jordan Reese | EurekAlert!
Further information:

More articles from Studies and Analyses:

nachricht Diagnoses: When Are Several Opinions Better Than One?
19.07.2016 | Max-Planck-Institut für Bildungsforschung

nachricht High in calories and low in nutrients when adolescents share pictures of food online
07.04.2016 | University of Gothenburg

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

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

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

First results of NSTX-U research operations

26.10.2016 | Physics and Astronomy

UCI and NASA document accelerated glacier melting in West Antarctica

26.10.2016 | Earth Sciences

Ice shelf vibrations cause unusual waves in Antarctic atmosphere

25.10.2016 | Earth Sciences

More VideoLinks >>>