In search for a material

Hi list,
I'm in need for your informed and knowledgeable advise. I would like to know what would be the closest thing to a material that the
following behaviour: it should be a photoreactive (ideally!!!), electroreactive, magnetoreactive... material that in environmental conditions is either soft or fluid and once stimulated (light, electric or magnetic field...) it either becomes sensibly harder and/or swells. It is also a requirement that once the stimulus is removed the material returns to its previous state.
Any pointers will be greatly appreciated.
Many thanks in advance
Johan Kildal
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DJ wrote:

I believe that this material is known as unobtanium.
Really fantastic materials such as you describe would probably be known and used in many ways, if they existed.
Unlike the 200 miles per gallon carburetor, there aren't industrial giants that suppress the knowledge of such materials.
If you relax your requirements of photoreactive, electroreactive and magnetoreactive...... you might find something, such as piezoelectrics in ceramic or polymeric versions.
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I recall seeing a prototype shock absorber in March 2002 at the SAE Congress that was using a magnetic material to increase damping. With no applied magnetic field the shock absorber was soft (they had one connected to a lever you could move by hand), then you increased a dial on the controller box (this field was applied electrostatically) and it increased the damping. In the max position it could support my weight (180lbs) on a 18" lever.
Dwayne
PS this link might help http://www.findarticles.com/p/articles/mi_m3306/is_11_114/ai_n9538305 or google Magneto-rheological fluid
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To follow up on dwayne, I believe you're looking for an MR fluid, simplistically put, it's a dispersion of iron particles in a fluid that align and give a "shear thickening" behavior to the matrix under an applied magnetic field. In principle, you can do that with ER fluids as well, although the response is not so significant from what I remember.
-srvclapton
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