Do Any Materials Contract with Small Electrical Currents?

[CyberJay]

Are there any materials that contract when a small electrical current is applied to it? What would be the necessary physical properties of such a material?

CJ

 

[dlgoff]

Try searching for piezoelectric crystals.

I have some pictures of various arrangments for contraction, expansion, bending, etc. But since 400x400 is the largest I can attach I had to reduce the size and it's not too clear.

 

[wj]

Shape Memory Alloys respond to changes in heat and electrical current (due to heat from resistance).

A NiTi alloy (nitinol) seems to be very popular. A google search for nitinol should give you a dozen supplies each spouting pages of technical specs for their products.

Muscle wire is also a good google search topic.

These alloys work very well to make neat little robots (you can buy kits) but I'm not sure how strong or how sensitive the alloys are.
If you find anything that might work as well as organic muscle please tell me about it.

 

[wimms]

Originally posted by wj
If you find anything that might work as well as organic muscle please tell me about it.

hmm, are you suggesting to take a rabbit and apply electric shock to it? Indeed, this might work too

 

[dlgoff]

How about frog legs. Probably wouldn't require as much current.

 

[NateTG]

Depending on the application, piezoelectric ceramics may also be a good option.

 

[wj]

After looking around a bit, found that piezoelectric ceramics expand with electrical current and produce current when contracted. These properties make them extremely useful for pressure sensors and sonics, as well as solid state generators. Though they can vibrate extremely fast, I think that they only change dimemesions a few mm.

Shape Memory Alloys react to heat, but these heat is generally created by current. These alloys contract when exposed to current, while piezoelectric ceramics expand with current. I don't know the specs for either one.

Since I'm interested in robots, muscle wire is my ElectroMechanic trastformer of choice. Frog legs are stronger but can you imagine decomposing fried frog thumping around your house :)

Plently of Information on piezoelectric ceramics can be found
here-> http://www.morganelectroceramics.com/pzbook.html

 

[dlgoff]

...while piezoelectric ceramics expand with current. I don't know the specs for either one.

Depends on which axis of the crystal the current is applied. I know the attachment I posted is a little small to read but it shows different configurations and the lenght(or angle) vs. voltage.

Regards

 

[wj]

I looked at your attachment. I couldn't read the words but the diagrams are clear. It showed a cube transformed in various ways by current. By changing the location and direction of the current you could shorten (squash), skew, or bend the crystal. Right?

So the cystal can get shorter or longer depending on the dimension you are considering?

Does the cystal change volume with current? I assume that the degree of the deformation varies with current. Is there a peak degree of deformation (like say 25% or 32%)?

 

[dlgoff]

Here's a couple of links for Piezoelectric Ceramics.
www.apc.thomasregister.com/olc/03482007/notes1.htm
www.apc.thomasregister.com/olc/03482007/notes3.htm