So-called "Sandfish" Could Help Materials Handling And Process Technology Specialists

It moves as quickly in sand as a fish moves through water, which is why this
lizard, a species of skink (Scincus scincus) that grows to about 15 cm long
and lives in the deserts of North Africa and the Near East, is commonly
known by the name "sandfish." Although it looks fairly unremarkable, this
desert animal has a thing or two to teach materials-handling and
process-technology specialists, as it spends most of its time below the
surface
of the sand and moves through its element extremely efficiently, and
scientists hope to apply the insights they gain from nature to improve
industrial
technologies for the handling of granular materials. Whether it's gravel,
sand or flour, optimising the technology for handling such materials could
significantly reduce energy and maintenance costs for businesses such as
quarries and industrial bakeries in the future.


In a new article published in the journal PLoS ONE, Prof. Werner Baumgartner
and colleagues from the Department of Cellular Neurobionics at RWTH
Aachen used an MRI scanner to observe the sandfish as it "swims" through the
sand.


"We took a round container that would fit snugly into the MRI and filled it
with sand," says Prof. Baumgartner. The project, which was carried out
in collaboration with researchers from the University of WГјrzburg and Museum
König in Bonn, has provided a visual record of the animal's movements
in the sand as viewed from above and from the side.


The scientists found the results highly surprising: until now, it was
thought that the sandfish pulled its legs in against its body, but the
experiments revealed that it actually moves its legs back and forth in a
fixed pattern. "This seems illogical at first, because sand provides
resistance," says Baumgartner. "But we found out that its leg movements are
very well coordinated with the wriggling of its body."


It turns out that the sandfish moves in a way very similar to the crawl
stroke in swimming. When the animal moves its head or upper body to the
left,
for example, it leaves a gap and thus an area of looser, less dense sand to
its right that allows the animal to move its front right leg forward with
little effort. Conversely, when the sandfish moves its upper body to the
right a moment later, the sand on that side is compressed; this compact sand
provides a stable basis from which to push off its front right leg. The time
displaced-movements of the lizard's legs according to this principle
add up to a very efficient and extremely rapid form of locomotion.


Interestingly, the biologists discovered that the sandfish always moves
through sand at the same frequency. "The lizard's winding movements
produce vibrations in the sand," explains Baumgartner. "Our experiments
showed that these vibrations have a consistent frequency of 3 hertz (three
motions per second)."


The scientists hypothesized that this frequency allows the animal to move
forward with the least amount of energy, and subsequent tests confirmed
their assumption. They did so by building an aluminium model of a sandfish
with a motor and having it move back and forth through the sand at
different frequencies. They found that the force required to move the
aluminium sandfish forward was lowest at exactly 3 Hz, as that was when the
sand
surrounding its body was loosest.















"The sandfish adapted to moving efficiently through granular material over
millions of years," says the Aachen-based neurobionics expert.
Scientists are increasingly applying insights gained from nature to a wide
range of innovative technological uses. "For example, we can use
mathematical and computer-based models to calculate the ideal frequency for
transporting all different kinds of granular materials," says
Baumgartner.


Thus materials-handling and process-technology engineers are not the only
ones who can learn from the sandfish; structural engineers stand to benefit,
as well. For instance, by using the optimal frequency for the job, they will
now be able to sink ground anchors into granular soil layers more
efficiently, which will save both energy and money.


Citation:

"Investigating the Locomotion of the Sandfish in Desert Sand Using
NMR-Imaging."
Baumgartner W, Fidler F, Weth A, Habbecke M, Jakob P, et al. (2008)

PLoS ONE 3(10): e3309. doi:10.1371/journal.pone.0003309
Click here to view article online


About PLoS ONE


PLoS ONE is the first journal of primary research from all areas of science
to employ a combination of peer review and post-publication rating and
commenting, to maximize the impact of every report it publishes. PLoS ONE is
published by the Public Library of Science (PLoS), the open-access publisher
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