Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Why anyone can make a sandcastle

14.02.2008
Max Planck researcher from Göttingen achieve a high level of understanding of the complex structure of moist granules

Anyone trying to build sandcastles on the beach will need some degree of skill and imagination, but not an instruction manual. The water content is actually relatively unimportant to the mechanical properties of the sand.


X-ray microtomography of a dense fluid cluster consisting of spherical glass beads (0.8 millimetres in diameter). Image: Max Planck Institute for Dynamics and Self-Organisation

This observation, which is borne out by precise measurements in the laboratory, puzzles researchers. Even with water content of just 3%, the fluid inside represents a highly-complex structure. The mechanical stiffness of the wet sand remains practically constant with moisture ranging from less than 1% to well over 10%, although the fluid structure changes enormously internally.

Researchers at the Max Planck Institute for Dynamics and Self-Organisation in Göttingen, the Australia National University in Canberra, the University of Erlangen, and the ESRF in Grenoble have studied the fluid structures in moist granules using x-ray microtomography to discover their laws (Nature Materials, online publication of February 10, 2008).

In medicine, x-ray microtomography is also known as computer tomography. Scientists x-ray an object from various angles to produce an outline image similar to a standard x-ray. A computer evaluates all of these images and determines which kind of three-dimensional structure the object must have to produce the outline images. When scientists use a bright x-ray source, such as the synchrotron source of radiation at the ESRF in Grenoble, computer tomography is produced with a resolution of thousandths of a millimetre. That is sufficient to resolve the tiny, highly-complex fluid structures that form in a moist granule, like inside a sandcastle for example.

What the research team saw was initially quite astonishing. The fluid did not fully push through the granulate structure and therefore did not force the air out of the interstitial space. More significantly, a filigree structure emerged in which the fluid, grains and air existed equally side by side. The reason for this is easy to understand. As the fluid moistens the grains (it would not otherwise be possible to get them into the granule), it tries to surround itself with as much "grain" as possible. This is best achieved at the points of contact where two grains touch. The "empty" space in between is relatively unattractive for the fluid and fills with air.

When the Göttingen scientists then carried out a more exact study of the geometry of these filigree fluid structures, they established that not only did they all have the same pressure, but that the pressure had to be independent of the fluid content. This explains the universal stiffness of the material. The equal pressure corresponds to an equal force inside and therefore results in the moist granules having the same mechanical properties. "These properties are not only significant to the building of sandcastles," said Stephan Herminghaus, the head of the study. "They are relevant to the pharmaceutical and food-production industries and help us to understand certain natural catastrophes, such as landslides. Wet granules are relevant in many fields and we now have a better understanding of their mechanical properties."

Original work:
M. Scheel, R. Seemann, M. Brinkmann, M. DiMichiel, A. Sheppard, B. Breidenbach, S. Herminghaus
Morphological clues to wet granular pile stability
Nature Materials, March edition 2008 Online publication at http://www.nature.com/nmat/index.html

Dr. Bernd Wirsing | Max-Planck-Gesellschaft
Further information:
http://www.mpg.de/english/

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Magnetic nano-imaging on a table top

20.04.2018 | Physics and Astronomy

Start of work for the world's largest electric truck

20.04.2018 | Interdisciplinary Research

Atoms may hum a tune from grand cosmic symphony

20.04.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>