This is a model prosthetic arm made entirely of Lego (yes, even the tubes and rubber bands!) -hand movements and wrist abduction/adduction are Lego pneumatics -wrist pronation/supination, wrist flexion/extension, and elbow flexion/extension are Lego motors (Power Functions)
The main purpose of this project was to accurately mimic the full range of motion of a normal human arm and hand. The secondary goal was to maximize speed and power, yet maintain a consistent ratio between the two for demonstration purposes. It is important to note that it was designed as an above elbow prosthesis, and the yellow shoulder is only meant to act as a static model.
The amount of weight it can lift is limited to the shape of the object and orientation of the wrist and elbow, but it can't do much with more than a couple pounds.
The controller is a rudimentary cluster of switches and joysticks. A 4-motor air compressor with pressure-regulation was made of Lego, but for the demonstration I simply used hand pumps.