Sciencemadness Discussion Board - Electrorheological Fluid

Electrorheological Fluid

sylla - 19-6-2006 at 07:42

Quote:

A class of liquid which stiffens into a semi-solid when subjected to a electric field. Electrorheological fluids are most commonly colloidal suspensions, and their stiffening under an electric field is reversible. Under the electric field, electrorheological fluids form fibrous structures which are parallel to the applied field and can increase in viscosity by a factor of up to 105. The stiffening of an electrorheological fluid is sometimes called the winslow effect after its first investigator, Willis Winslow in 1949. Electrorheological fluids can be characterized by their Mason number.

The effect has been proposed as a method of constructing shock absorbers on magnetically levitated trains. Lithium polymethacrylate is an example of an electrorheological fluid.

Does anybody have info about these fluids ? Or maybe personnal experiences with that stuff ? Any synth that could be done in a home lab ?

I'm sorry if my post is a little bit short but I don't have many informations about this topic...

[Edited on 19-6-2006 by sylla]

enhzflep - 19-6-2006 at 23:31

Well, other than Sony is considering their use in a new generation of games-console controllers, and that their use for bullet-proof vest is being considered - other than this I don't have much.

I did find one link that suggested that in fact the viscosity may be increased by as much as a factor of 10^5 and another link that quoted a figure of 10,000! In any case, these are some fluids that become seriously thick upon the application of an electric field - more so with increasing applied potential - and all in milliseconds!

In the case of the bullet proof vest, it is hoped that their adsorption into fabric will provide a light, non-restrictive garment that can at command become rock-hard. (provided bullet-fire may be detected before the projectile appears on the scene)

Here's the sum total of usefull links I have on the topic Sylla.

1) Electroviscous fluids - Patent 4502973
http://www.freepatentsonline.com/4502973.html
This link details the synthesis of a number of these compounds in addition to other assorted errata. This seems like the golden article. It will depend on the available chemicals that you have, I've not read it word for word, but it seems fairly comprehensive with molar quantities, temperatures times and handling procedures all detailed.

2) Direct synthesis of electroheological suspension containing salt
http://doi.wiley.com/10.1002/app.1995.070580512
This links to an article in Applied Polymer Science magazine. Just checked, it's $25 US for 24hrs access to the article

3) A new low-cost electroviscometer
http://www.iop.org/EJ/abstract/0957-0233/2/8/005
This links to an article describing the construction of analytical tools to be used during the analysis of Electroheological fluids. This puppy's $30 US

All above information and more may be found through this link:
http://www.google.com/search?lr=&ie=UTF-8&oe=UTF-8&a...

[EDIT: Need to copy and paste last link as board formatting software neglects to include "%20fluid" in the click-able part of the link.]

[Edited on 20-6-2006 by enhzflep]

Twospoons - 20-6-2006 at 15:08

It can be done with a simple mix of cornflour and oil!

sylla - 22-6-2006 at 02:51

Thx you for your reply enhzflep. I had already searched on google but there aren't that much info about it...

Quote:

It can be done with a simple mix of cornflour and oil!

Huu ... ?

YT2095 - 22-6-2006 at 02:58

I think he`s refering to whats called a Non Newtonian Liquid, although I`ve never heard of it done with Oil, it`s usualy just plain water.
in effect you can move very slowly through this liquid, but any sudden impact and it will solidify. and then become a `liquid` again shortly afterwards.
I`ve never heard of it having any electrical properties though???

[Edited on 22-6-2006 by YT2095]

Twospoons - 22-6-2006 at 15:30

Look here about halfway down the page. And here.

YT2095 - 22-6-2006 at 23:58

Fascinating!
I`de heard of the 1`st one mentioned in here: http://abcasiapacific.com/nexus/stories/s710297.htm
but the oil idea`s a new one to me

it doesn`t state what sort of oil is needed or the charge required though?
a substance such as this may have practical applications in Robotics too, neat stuff, Thnx

enhzflep - 23-6-2006 at 01:42

YT2095 - Refferences I've read mentioned the use of silicone oil and applied voltages in the kilovolt realm. Something I wasn't able to uncover was any mention of their power consumption - (I am assuming that they don't function like a perfect capacitor with a usefull substance placed between the plates)

However, with the consideration by Sony to incorporate them into a hand-held controller, one can only assume that the power consumption would be rather minimal.

YT2095 - 23-6-2006 at 09:09

yeah, the overall power consumption is an issue here, and would be intersting to find out.
Kilovolts is Nothing, standard plasma (gas discharge tubes like the display on my video recorders) use a kilovolt or two also, as do plasma balls or pocket flourescent torches.
based on that I would Guess that for a hand-held device the power levels would be somewhere in that ballpark.
Silcone Oil though, I`ve been after some of that stuff for ages, it makes an interesting reaction with Boric Acid

enhzflep - 23-6-2006 at 17:39

Far from being the cheapest source, silicone oil may be purchased at model-shops. In this instance, it is sold as shock-absorber oil for RC cars. It has been purchased before for use in 1/8 scale Nitro cars. IIRC it was ~$7 Aus for less than 50ml.

Just outta interest YT2095, what does happen when mixed with borax?

12AX7 - 23-6-2006 at 18:22

http://en.wikipedia.org/wiki/Silly_Putty

Boric acid, not borax (that's poly vinyl acetate(?), aka white glue). Although I don't know if it makes a difference.

Tim

enhzflep - 23-6-2006 at 18:35

Ah, HAH!

So that's what it does. Thanks 12AX7!

My memory frequently fails the CRC check

Damned 1970's neurons. It seems that I should have said Boracic acid rather than Borax.

Oops - so that means a trip to the chemist instead of the supermarket. We frequently use boracic in ethanol as a way of preventing oxidation on precious metals whilst soldering them. It allows one to solder a polished article, heating to dull red heat without losing the polished surface - even on gold down to 9 karat and on sterling silver.

[EDIT: dull read heat --> dull red heat]

[Edited on 24-6-2006 by enhzflep]

12AX7 - 24-6-2006 at 05:02

Easy enough to get boric acid from sodium tetraborate. Make a solution and add HCl, boric acid will ppt out.

I keep a tin of borax on hand for brass brazing too.

Tim

kazaa81 - 24-6-2006 at 06:06

So, it's just put some H3BO3 (boric acid) into silicone oil?

Boric acid can be made from aq. sodium perborate + HCl, so isn't really a problem...
Where can I buy silicone oil for cheap? I know it's usually sold into small bottles not so cheap, used to grease syringes and such apparatus...

YT2095 - 24-6-2006 at 09:16

not a clue, but if you find out, let me know.
the only thing I`ve seen is Silicone grease, and thats used to lube Curtain rails, I didn`t even bother trying that, the wife used it all, on the curtain rails of all things!