I don't know if this was already discussed here but I'm just reading June's
edition of IEEE Spectrum and one of the articles talk about artificial
muscles (electrically activated polymers) and I wonder how easy is to work
with such thing:
1) Is it already available in the market for hobbysts or researchers?
2) Does anybody here have any experience with these?
I'm still reading it, but so far I'm enjoying leaning the fact that we are
not so far from it (if not already there)
There are several types of EAP artificial muscles. Most of them fall
into two categories: Ionic which must stay wet and require low voltages,
and dielectric which work dry but need very high voltages (10 KV range)
I work with dielectric EAP's. They can be very dangerous. A dielectric
artificial muscle is basically a very large mushy capacitor. There is
very little current while they are being used, but there is a huge
amount of stored energy. Any shorting in the system will release a huge
(i.e. deadly) amount of current. In addition, electricity starts acting
a little different in the multi-kilovolt range. Insulators become just
poor conductors. Edge effects cause seams where insulators are joined
to act like wires. We often see "thermal events" (fires) during our
tests. Dielectric EAP is not something to experiment with at home.
With their lower voltages, ionic EAP is not so bad, but then you have
electricity and water so you still need to know what you are doing.
There are one or two commercial products out now that use this technology.
If you are really interested, see if you can get the book:
"Electroactive Polymer (EAP) Actuators as Artificial Muscles - Reality,
Potential and Challenges" through inter-library loan (its $75 online).
The second edition is now out. It would be a safe guess to say that
about 75-80% of what is known about the subject is covered in this book.
For the time being, you are better off working with muscle wire unless
you have a really well equipped lab.
Correct me if I'm wrong, but isn't most EAP actuation inherently
non-linear? They tend to bend instead of retract, which can be an
awkward motion to make use of.
Muscle wire is certainly a much safer element, although they're far too
slow, weak, and hot to be of much use in the long run.
Air muscles are interesting, except for the noise and inaccuracy due to
compressibility of air.
EAP actuation depends on how the "muscle" is formed. For dielectric
EAP, the material compresses along one axis (perpendicular to the
compliant electrodes) and expands on the other two axis to keep a
constant volume. If you have one big sheet of EAP material with
continuous compliant electrodes on the major faces, you can roll it up
and make a device that will extend along the axis of the roll. If you
do the same thing, but instead of having one compliant electrode on each
major face you have electrode strips that can be independently
activated, you can make the tube bend by only activating the electrode
pairs that are on one side of the roll.
Air or McKibben (SP) muscles are cool, and a lot safer than EAP for the
experimenting at home. The only big problem with them is how fast they
wear out. They are usually made of a rubber bladder with a crosshatched
nylon shell around them (like a fat Chinese finger torture toy - woven
nylon cable protectors work good). The nylon rubs on the rubber each
time the muscle is moved. Eventually it weakens a spot on the bladder
until it pops. You could improve their accuracy by using a liquid
instead of air, but the weight goes way up and it is a much bigger mess
when they pop.
There's been an earlier kind of "artificial muscles" called Flexinol,
which are made of Nickel-Titanium wires, for over 10 years.
They draw a significant amount of current and are kind of slow, but
easily available. That might be a starting point for such a project.
Polymer-based muscles are too difficult to get ahold of and use for the
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