At very small scales the effect of turbulence
disappears, making liquids more difficult to travel through. The viscosity
of water at small scales is more like honey than a quickly-flowing liquid.
This makes it difficult to design microscopic machines that can
move through water. The trick is to design a cyclical motion that is not
identical in the reverse direction. In the absence of turbulence, which
allows for gliding, reciprocal motion simply holds a swimmer still.
Researchers from the Institute for Advanced Studies in Basic Sciences
in Iran and the Max Plank Institute for Physics in Germany have designed
a swimming machine that meets the challenge. The swimmer consists of three
rigid spheres linked by narrow rods.
The design could eventually be used to propel machines whose size
is in the molecular realm. These machines could be constructed from molecules
that change length in the presence of light or from motor proteins used
Key to the swimming ability is a nonreciprocal four-step periodic
motion: the right arm stays fixed while the left arm shortens, the left
arm stays fixed while the right arm shortens, the right arm stays fixed
while the left arm lengthens, and finally the left arm stays fixed while
the right arm lengthens.
The mathematics behind the motion can be worked out relatively
easily, which makes it easier to use the motion in practical machines.
It will be one or two decades before the design can be used in
practical devices, according to the researchers. The work appeared in
the June 16, 2004 issue of Physical Review E.
Projector lights radio
Cell phone melds video
Sound system lets
Chips measure electron
Twisted fiber filters
bring walking to VR
Speck trios make
Single gold atoms
Pen writes micro wires
Design eases nano
View from the High Ground Q&A
How It Works
News | Blog
Buy an ad link