The intro pic shows a six segment elbow muscle, a three segment actuator muscle, and a single segment muscle under low air pressure. The thumb pic shows the artificial muscles with no pressure.
You can see a robot arm and gripper that was made using this type of artificial muscle, here: http://www.instructables.com/id/Soft-Robots-Make-An-Artificial-Muscle-Arm-And-Gri/
Step 1: How artificial robot muscles Work
An artificial muscle segment is cast in two layers with a thin piece of plastic between the layers to allow for air expansion. This creates a simple air bladder that can glued together in many segments with spacers to create curving or straight robot muscles.
The step one pic shows a 3d illustration of a six segment silicone robot muscle. Ideally, an artificial robot muscle like this could be directly printed in one piece. I have not found a 3d printer service that can print silicone or rubber at an affordable price. So, for now, I can only do the illustration and must use hand techniques to create the muscles. I am looking into the 3d printing of plastic molds that could be used to cast the Oogoo robot muscles in one step.
123D was used to create the illustration.
Step 2: Materials
100% silicone caulk
1/16" thick plastic sheet. I used phenolic sheet that I had, but polycarbonate, acrylic or any other plastic sheet material could be used.
Spray Lacquer from hardware store.
12 volt air/vacuum pump from: http://www.sparkfun.com/search/results?term=vacuum+pump&what=products
12 volt solenoid air valves from: http://www.allelectronics.com/make-a-store/item/SOL-132/SOLENOID-VALVE/1.html
Aquarium air hose from: Amazon.com
Raintree drip irrigation fittings from Amazon.com