ACEIZE Tracking the current state of Science and Technology

Not very long ago, I posted a youtube video of ferro magnetic fluids in action. I thought it was an amazing, cool, and new idea. Well over the course of a couple weeks I kept hearing references to ferro fluids. One such reference was when looking into the Future Warrior project from DARPA. It was suggested that ferro magnetic fluids would make it possible to have an advanced type of anti-ballistic body armor. The body armor would remain soft until a magnetic field was applied, thereby making it rigid and 'bullet proof'. A few days later I heard about a not so dramatic use of the material - automotive shock absorbers. So I got to looking up some bona-fide information on the subject.

It turns out that there are several classes of ferrofluids. More accurately there are two classes of Electrorheological fluids. Wikipedia gives a great definition: "Electrorheological fluids are suspensions of extremely fine non-conducting particles (up to 50 micrometres diameter) in a non-conducting fluid." The non-conducting fluid is generally organic solvents such as soy lecithin or oleic acid. These fluids have the property of changing density in response to a magnetic field. This is dubbed the Winslow effect, named after Willis Winslow who discovered the effect in 1947. Theoretically the particles should not settle from the suspension. In order to do this, an attempt is made to match the relative densities of the particles and suspension fluid. In reality, particles generally settle or the suspension begins to harden over time, leading to a need to replace the fluid.

The two classes of Electrorheological Fluids are Magnetoherological Fluids and FerroFluids are defined by the size of the particulate suspended in the fluid. FerroFluids contain particles which are nano-scale -- "typically of order 10nm" according to wikipedia.
Magnetoherological Fluids are larger in scale, generally in the micrometer "usually in the 0.1-10 µm range" according to wikipedia. The smaller size of Ferrofluids make them more difficult and expensive to manufacture.

There are many current uses of Electroheological Fluids. Wikipedia, again has a great rundown, but I will summarize here.

Current Uses

• Printer Ink - from Matsushita Electric
• Seals on harddrive shafts
• Friction reduction (when applied to a strong magnet such as neodymium it can glide across a smooth surface)
• Heavy Motor Dampening
• Radar Absorbent Material (RAM) paint developed by the US Air Force
• Heat transfer in microscale devices
• Loudspeakers for dampening
• Automotive shock absorbers

Possible Future Uses

• Anti-Ballistic Body Armor
• Articulation of Robotic or Prosthetic Limbs