Tech Army Togs (10.23.02) – Today's soldiers are armed with so many
high-tech gadgets that they're advertised as "an army of one." Now
it looks like one of those high-tech devices may be the uniform itself.
When danger looms in the new Matrix movie, the heroes step into flexible armor.
The U.S. Army wants something even more amazing for our soldiers—uniforms
that turn into lightweight armor on command. As this ScienCentral News video
reports, one nanotechnologist says that instant armor could be real in ten
On the battlefield of the future, soldiers could be wearing uniforms that turn
from soft, comfortable fabric to light, flexible, durable armor with a flip
of a switch.
"What we're working with is a class of fluids called magnetorheological
fluids," says McKinley. "These are liquids that change their properties
when we apply a magnetic field to them. They are made up of very, very small
iron particles, much smaller than individual red blood cells," which
the researchers then mix into a silicon oil, or even corn syrup, so they don't
rust. The oil or syrup also makes the solution mayonnaise-thick, with just
enough stiffness to prevent it from running.
Oily fluid full of tiny iron particles before being near a magnet (above); and after.
McKinley is director of MIT’s Hatsopoulos
Microfluids Lab, which studies the properties of complex fluids and how
fluids move in very small channels. Just as matter behaves in unusual ways
at the scale of atoms and molecules, fluids also move differently at very
small scales. When McKinley and his researchers apply a magnetic field to
their solution, the tiny iron particles align with the magnetic field, and
stack up on top of each other. As they do so, the fluid turns into a peanut
butter-like substance that feels very hard. When the researchers remove the
magnet, the solid instantly reverts to liquid. McKinley says that the change
happens incredibly quickly—“in about 20 thousandths of a second.
We can keep applying a magnetic field, turning off a magnetic field, and the
material will keep going backwards and forwards, from liquid-like to solid-like
and back again."
McKinley and his team are investigating ways to put this switchable solution
into the material currently used to make bulletproof vests, which is essentially
a woven fabric full of air gaps. Once the researchers immerse that fabric
in magnetorheological fluid, "what we have without a magnetic field is
a very soft, very flexible fabric, and when we apply a magnetic field, then
the stiffness of that fabric changes by a factor of about 50 at the moment,"
says McKinley. "The stiffness change depends on the strength of the magnetic
field. As the magnetic field gets stronger and stronger, then the stiffness
change gets larger and larger.” The research team hopes that eventually,
the fabric-fluid combination could resist a shockwave or shrapnel.
Since troops won't be carrying magnets on the battlefield, McKinley says he
would wire the fabric of military uniforms with electric current that soldiers
could switch on to produce electromagnetic fields. "Ultimately, the way
the magnetic field would be applied in a suit, would be that the electromagnets
or micro magnets would be part of the actual fabric suit system," says
McKinley. "Working with Patrick
Doyle, professor of chemical
engineering at MIT, we've already explored the possibility of using very
small magnets as valves to turn these fluids on and off."
McKinley emphasizes that this "instant armor" is definitely not combat-ready
yet. "We've got five to ten years of research before we can make this
material truly bullet-resistant," he says. Right now, he’s working
Alan Hatton, also of MIT’s chemical engineering department, on making
his tiny iron particles in different shapes. “The particles that we’re
using now look like soccer balls. They’re spherical," says McKinley.
"If you were to stack a pile of those together, you don’t get very
far. What would be better would be to have faceted particles, particles with
flat faces, or particles that look more like donuts. You could stack a pile
of donuts on top of each other.”
McKinley and his team also would like their fluid to change even faster, and
to remain reversible for years.