[mark-r]

It does seem from the description that only one motion is possible for one of these muscles. Full motion would require combining multiple muscles with complementary motion, similar to the way the body works.

The speed seems much slower than that of an actual muscle. Is this inherent in the technology or just a limitation of the current prototypes?

[creep]

I can imagine this being modified for spring-like muscles, with a more elastic material. Other than that, you can just suck the air out faster (which has a limit) would work better with shorter muscle "segments".