Nature can be a great source of inspiration. This Air Muscle is an actuator that works very similarly to a human muscle—it contracts by thickening. Inside the black pouch is a balloon. High pressure air pumped through the tube inflates the balloon causing the muscle to shorten by as much as 40%.
Air Muscles can provide substantial pulling force for their small size; they can exert force 400 times their weight. Typical DC motors or pneumatic actuators can exert about 16 times their weight. The largest of the standard Air Muscles is 11 inches long, weights less than 3 ounces, and can lift 154 pounds!
Air Muscles work when twisted, bent around corners, or under water. It even has a similar power profile to a human muscle: the force exerted decreases as it contracts, just like the strength of your biceps is maximum when your arm is extended and decreases as your arm is bent.