The RAPHaEL hand, or Robotic Air Powered Hand with Elastic Ligaments was constructed by Virginia Tech researchers. Its main claim to fame is a 60psi deft and dexterous movement, with a complete lack of motors. It uses actuators based on the accordion model instead.

Microcontroller commands operate the movement to coordinate the motion of the fingers, which have fine, delicate movement, gentle enough to hold a raw egg withoui breaking it, and strong enough to securely hold a full can of food.Likewise, movement is swift enough to render real-time sign language.

"This air-powered design is what makes the hand unique, as it does not require the use of any motors or other actuators, the grasping force and compliance can be easily adjusted by simply changing the air pressure," said Dennis Hong, one of the developers. "There would be great market potential for this hand, such as for robotic prosthetics, due to the previously described benefits, as well as low cost, safety and simplicity."

The grip derives from the extent of pressure of the air. A low pressure is used for a lighter grip, while a higher pressure allows for a sturdier grip. The compliance of compressed air also aids in the grasping as the fingers can naturally follow the contours of the grasped object.

RAPHaEL is just part of a larger RoMeLa project: The humanoid robot known as CHARLI (Cognitive Humanoid Robot with Learning Intelligence). The hand already is on its second prototype design, with the newer model to be used by CHARLI. Once the newer model hand is connected to the larger body, it will be able to pick up — not just grasp and hold — objects as would a person.

Hong has said CHARLI is the first full-sized bipedal walking humanoid robot to be built entirely in the United States. The 5-foot tall robot will be used as a general humanoid research platform as well as for the RoboCup Humanoid Teen size league for RoboCup 2010.