MIT and University of Tokyo researchers devised stick-on "pouch motors," simple inflatable actuators that can be used to move things by pumping air in and out.
From IEEE Spectrum:
The actuators get printed on a custom-made fabrication machine that's nothing more than a 3-axis CNC holding a rod that can be heated, like a soldering iron. Moving the iron over two sheets of thermoplastic bonds them, leaving patterns of interlocking, inflatable pouches, and there's your actuator. Hooking up a tube to the actuator with a syringe on one end allows the user to inflate and deflate the actuator, which will drag along anything that you've decided to stick it to.
To see what more advanced air-powered actuators can do for big robots in the real world, check out the work of Pneubotics (image below) that I profiled in this Businessweek article: "Robots That Show Their Softer Side"
