Magnetic muscles Consider two flexible sheets glued at the ends, with electromagnets attached to both of them, so that depending on the directions and strength of currents passing through them, the system could be either
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I could imagine multiple such systems combined to control a robotic limb. The up side of such construction would be few moving parts, possibly cheap construction. Is this ever done? What are the downsides?
 A: As far as I have read and seen on google, I can assure you we have not observed something like this till now, I am also a regular reader of popular science and such a technology they have not featured untill now.
First of all I would like to list what actually would be its upsides :
1. Compared to robotic arms we have today it can be used to do far more precise and complex operations, as todays arms movd with help of actuators, servos, relays they cannot move in all directions, these musles can be designed on a smaller scale and then used as tissues and then musces/tendons which are even more flexible and movable than todays animals and robots.
2. Their circuitry could be designed (preferably embedded in them) such that even if some muscles tear apart, rest arm operates as each muscle can be made self sufficient. Todays robot's motors and other operators are separately controlled by motor drives etc which if disabled render the whole arm useless.
3. They could even replace todays prosthesis as they can be used to develop parts which resemble the biological ones more closely.
Now on to possible downsides :
1. It may require higher power or smaller muscles (which I recommend) in more quantity, either way it would not be inexpensive.
2. As simple motions such as rotation etc which are easily controlled by motor controls in todays robots will need complex methods to be achieved, more delicate and complex circuitry and programs will be required.
3. As the program will be more complex, it will definitely reduce increase time of whole arm. Also since multiple muscles will be required to perform one task it would reduce time efficiency even more.
4. The muscles would need to work in perfect sync as if some muscles move and others dont the arm may rupture internally or in some other way malfunction.
5. Damaged arms would be harder to repair than conventional robotic arms because of their complex structure.
Although quantitatively downsides are more than upsides, I think that it is a truly remarkable idea and should be used in future as it can lead robotics much farther than it has come.
