Advances in Artificial Muscles Using Plastic

pinglej writes "According to this story on MSNBC, Scientists at SRI have made some advances in muscles made using strained plastic that are more responsive than natural muscles. Has lots of neat applications from speakers to artificial limbs. " I think the best idea is to make me the strongest man alive - it'll be better than cybernetic body armor!

Comments

Let me see....

[jd]

• Plastic melts. That means no more hot showers.
• Plastic does nasty things in UV light. That means no more going down to the beach, or anywhere near an Ozone Hole.
• Plastic doesn't restore perfectly, it stresses. Too much arm-waving, and your arms'll fall off.
• Plastic is a non-conductor. Non-conductors, seperating conductors, have some interesting properties. How many farads is your armpit?
• More responsiveness must mean less of something else. Probably less precision. Good for Quake 3, but painful for bitmap editing.

Applications

[Captn Pepe]

Materials like this exert force because they try to maintain an approximately uniform density, so an electric potential squeezes it into a different shape. The trouble with using this to do mechanical work -- like the "artificial muscle" this is being hyped as -- is that you can't exert very much force before the material starts to compress, or else you overwhelm the electrostatic forces. This is sort of the converse of the problem that piezo-based transducers have always had: the electrostatic potentials cause the crystalline lattice of a piezo to expand with considerable force ... but only for a few hundreds of microns, at best. Which makes them good for speakers, or ultra-fine positioning, but not so good for doing work.

As far as I can tell, the most promising avenue for these materials would be to use them rather like small, agile hydrolic pumps that have large dynamic range but little pushing power and even less pull. The comment in the article about an artificial butterfly could be insightful with respect to what you could do with these. As far as artificial limbs go, unless they can dramatically increase the force they can put out, they might be a major breakthrough for actuating the fingers of a prosthetic hand, but they'll be no good at all for replacing the wrist flexors, never mind a bicep.

I would suggest that researchers look for a way to turn this effect around, allowing the material to pull rather than push. Such plastics almost invariably have greater tensile strength than resistance to compression, and it's much easier to engineer around, too.

Nitinol muscle wire & Stiquito

[c.jaeger]

My first contact with the concept of an artificial muscle started when Prof. Jonathan W. Mills from Indiana Univ. gave an IEEE talk at my college around 1992. When he demonstrated the foreshortening of a small nickle-titanium (nitinol) heat actuated leg all the geeks in the auditorium were impressed. (College profs included)

We had a small lab session where we made the legs from materials he brought and did a Q&A session. I still have that device around played w/ it 2 nights ago. Didn't have a battery around to run current through the nitinol wire to actuate it (the electrical resistance generates enough heat to contract it), so I held a lighter about 6" underneath to test it out. Still worked like a charm.

If you are interested in looking into this thing, I'd suggest hitting

• www.computer.org/books/stiquito
• reading through the comp.robotics.misc Newsgroup
• and the newsgroup comp.robotics.research (moderated) which has some archives & FAQ at www.metamech.com/crr

Let's get intelligent here.

[Ron Harwood]

1) I read some guy saying "Plastics melt" (among other "weaknesses")- ok, we're not talking saran wrap or the stuff they make pens out of here... the word of the day was "Acrylic"... some polymers can be made to withstand tremendous heat/strain/environments...
2) When they say "muscle"... it doesn't necessarily mean they've got to put it in a human body. They could mean for use in a machine - and muscle is the best word to describe how it works... (Robots, exoskeletons, automatic door closers...)
3) If they were developing it for the human body, it would have to be developed in a tested and controlled fashion. Allowances for added stress would have to be made (re-enforcements to skeletal structure) as part of the design/engineering of the product. Otherwise, the muscle would need be developed to not exceed the strength of the skeletal structure. (beyond the fact that I seem to remember that when bones are stressed they emit a small electrical signal - which would cause these "muscles" to stretch and relieve the tension...)

Don't just look for nay saying ways to FUD the product... any idiot can point out problems... if you were really smart, when you found the problem, you would make a suggestion on how to fix it.