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NASA Science News for April 2, 2003

Amazing Magnetic Fluids

Astronauts onboard the International Space Station are studying
strange fluids that might one day flow in the veins of robots and
help buildings resist earthquakes. 

April 2, 2003:  If you don't see it for yourself, you might not
believe it. 

A grey blob oozes down the side of a laboratory beaker. It's heading
for the table, but before it gets there a low hum fills the air.
Someone just switched on an electromagnet. The goop stiffens,
quivers, then carries on oozing only after the hum subsides. 

Is it alive?

No, just magnetized.

"We call them magnetorheological fluids--or 'MR fluids' for short,"
says Alice Gast, a professor of chemical engineering at MIT. "They're
liquids that harden or change shape when they feel a magnetic field."

You can make some of this exotic stuff at home. Just mix some
powdered iron filings with a thick liquid like corn oil, and presto:
a simple MR fluid. Hold a magnet nearby and the bits of iron will
line up end-to-end; they form a rigid lattice that stiffens the
mixture. Take the magnet away and the fluid will relax again. 

If you own a sports car or a Cadillac, you might have MR fluids in
your shock absorbers. The stiffness of magnetic shocks can be
electronically adjusted thousands of times per second, providing a
remarkably smooth ride. Similar but more powerful devices have been
installed at Japan's National Museum of Emerging Science and China's
Dong Ting Lake Bridge. They're there to counteract vibrations caused
by earthquakes and gusts of wind. 

Motion damping is perhaps the most practical use for MR technology
today, but much more is possible. Says Gast: "There are many
potential applications that make these fluids very exciting." For
example, MR fluids flowing in the veins of robots might one day
animate hands and limbs that move as naturally as any humans. Book
makers could publish rippling magnetic texts in Braille that blind
readers could actually scroll and edit. It might even be possible to
train student surgeons using synthetic patients with MR organs that
flex and slice like the real thing.

There are many problems to solve before such things are possible. How
do you control a magnetic field and deliver it with exquisite
precision anywhere inside an MR fluid? Researchers aren't sure--but
that's another story. Equally important are the inner workings of the
MR fluids themselves. "We need to learn much more about their basic
physics," says Jack Lekan of NASA's Glenn Research Center. 

That's the goal of an experiment called InSPACE now orbiting Earth
onboard the International Space Station. Gast developed InSPACE,
short for "Investigating the Structure of Paramagnetic Aggregates
from Colloidal Emulsions," in collaboration with scientists and
engineers at the Glenn Research Center. Gast is the principal
investigator; Lekan is the project manager. 

InSPACE will explore a curious phenomenon: When some low-density MR
fluids are exposed to rapidly alternating magnetic fields, their
internal particles clump together. Over time they settle into a
pattern of shapes that look a bit like fish viewed from the top of a
tank. Such clumpy MR fluids don't stiffen as they should when
magnetized. 

The fishtank pattern is fragile and takes about an hour to fully
develop. It doesn't occur in MR fluids that are constantly mixed and
agitated, as in a car's suspension, but it could prove troublesome in
other situations. 

The pull of gravity on Earth can distort the pattern--a frustration
to scientists trying to study its underlying physics. That's why Gast
and colleagues have sent their MR fluids to orbit. On the space
station, astronauts can expose a weightless (freely-falling) fluid to
magnetic pulses and record what happens. 

"Astronauts are an integral part of our study," notes Lekan. They
will reach into the Microgravity Science Glovebox, where the
experiment is located, to align and focus cameras on a spot only 0.2
mm wide. If a fluid bubble gets in the way of the shot ... flick!
they can remove it. 

This week, ISS Science Officer Don Pettit conducted the first
experiments with MR fluids inside the glovebox. His two-hour "run"
marked beginning of the InSPACE investigation, which will likely
continue off and on throughout the month. 

Meanwhile, some companies are already forging ahead with new
magnetorheological devices. Lord Corporation of North Carolina, for
example, is designing an MR washing machine. Magnetic dampers inside
the machine will decrease noise and vibration--and save energy. They'
re also studying MR technology for seat belts and airbags in cars.
Because MR fluids can generate large forces quickly and flexibly,
they could be used by automakers to adjust the arresting force of a
seatbelt to the size and weight of a passenger. 

Saving lives and silencing washing machines--and that's just the
beginning. Not bad for a bunch of grey oily goop. 

Credits & Contacts
Authors:Dr. Tony Phillips, Patrick L. Barry 
Responsible NASA official: Ron Koczor 
Production Editor: Dr. Tony Phillips 
Curator: Bryan Walls 
Media Relations: Steve Roy

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