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Nanotube Muscles Are Strong As Steel, Light As Air
Al writes "Scientists from the University of Texas at Dallas have created nanotube-based artificial muscles that are light as air and work even under extreme temperatures. The 'muscles' expand width-wise by about 200 percent when a voltage is applied, but are stronger than steel lengthwise. The nanotubes within the fiber naturally stick together. Applying a voltage makes them obtain a charge and repel one another. The researchers created them by stretching bundles of entangled carbon nanotubes into long threads. Several cool videos show the strange stuff in action. Some experts, including one from NASA, believe that the nanotube muscles' ability to withstand extreme heat and cold could make them suitable shape-shifting materials for future space missions."
From Article -
However, electroactive polymers generate up to eight times as much force per unit area as the nanotube sheets. "For artificial muscle, you need a large change in force coupled with a large change in length," Hunter says.
Polymer actuators also need just a few volts to contract. The ribbons, in contrast, require three to five kilovolts, which Hunter says is too high for use in humans and higher than ideal for robotics.
Real muscles contract by myofilaments sliding past each other, shortening the overall length of the muscle. In this case no sliding past occurs, and the overall length of the nanotube "muscle" doesn't diminish, so I can't see how this technology could be used to replace actual muscles.
Maybe because they're not biologists.
No ascii art.
The fact that it is "strong as steel" and "light as air" seems to me like it could be made into a (very) big net that, when launched into orbit could capture space junk. Hopefully the fact that it stretches 200% could mean that it would have enough elasticity to absorb some of the kinetic energy of the space junk.
As long as the space junk didn't make holes in it, it would slow the junk enough so that they would fall out of orbit quickly. (Maybe the impact of a lot of junk would require periodic re-boosting of the net, I don't know.)
Another idea would be to use AEROGELS. This super lightweight material has already been proven to slow down hyper velocity objects (admittedly just particles) in the spacecraft "Stardust". The main problem with aerogels would be launching it into orbit, although it is very light the necessary volume required would be huge. However, if it could be manufactured in space then just a small amount of raw material could make a gigantic volume of the stuff.
All three articles are confusing and lacking information needed to make any sort of meaningful conclusion. It seems the people writing them don't bother to think, but just string together random fact snippets that sound cool and generate hype.
One puzzle is that on the one hand, "carbon nanotubes are highly conductive", yet on the other hand need "three to five kilovolts" to contract. If the resistance were say one ohm, that would be 9 to 25 megawatts of power! A robot with 50 muscles might consume the entire output of a power plant, not to mention burn up instantly.
They also confuse the force exerted lengthwise (large) and the force exerted width wise (possibly very small, since it seems to be due to electrostatic repulsion - the videos do not show the width-wise force being measured or demonstrated).
Possibly the 1% lengthwise contraction could be amplified, to say 30% by wrapping it around a set of 30 pulleys.
I see the threads aren't perfect individual nanotubes, but still, good enough for a tether maybe?
Yeah I had visions of vehicles being pushed up a space elevator by peristalsis.
http://michaelsmith.id.au
why can't these scientists just devote their work to curing the common cold or the flu?
How will our immune system end up looking without a frequent visitor to give it a work out?
Pure tungsten is about eight times as strong as mild steel -- the stuff that your car, refrigerator, and computer case are made of -- in terms of tensile strength. It's also very tolerant of high temperatures.
But because of its brittleness, it's useless as a structural material. Why do these articles always refer to strength, without describing what kind of strength that is? Tensile, compression, shear, torsional, etc.