Name: Ian
Status: student
Grade: 9-12
Location: PA
Country: USA
Date: Summer 2011
Question:
Hello and thank you in advance. I have previously read of
a material ( a kind of "rubber") that contracts when an electric
current is applied.
My question is what is this material, how does it work/what is it
made of? Thank you very much.
Replies:
Hi Ian,
I believe the material you are referring to is a kind of piezoelectric
rubber. Piezoelectric materials (usually they are special types of
ceramics or crystals) produce an electrical voltage when compressed of
otherwise subjected to stress. They also do the opposite... they
slightly expand or contract when a voltage is applied.
But the amount they expand or contract is very small indeed. For
example, one square meter of the recently discovered piezoelectric
rubber materials typically contracts a mere 100 picometers for ever
applied volt. Translated into everyday measurements, this means that if
you apply a voltage of 1 Volt to a one foot long piece of this rubber,
it will only contract less than half a billionth of an inch! Applying
100 volts will cause it to contract just under 50 billionths of an inch!
While technically interesting, you can see that this effect is rather
limited! This material is made from a type of rubber that has a layer
of piezoelectric crystals applied to one side. Its proposed use is to
generate electrical current when stretched, which is the opposite
effect that you are interested in (you are interested in it changing
shape when an electrical current is applied).
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