* Coffee-filled balloon forms basis of new robotic hand
* Could be used for prosthetic limbs, in factories
CHICAGO, Oct 25 (Reuters) - A floppy robotic hand that stiffens when air is sucked out -- much like a vacuum-packed brick of coffee -- may form the basis of a new type of robotic gripping mechanism, U.S. researchers said on Monday.
The gripper -- essentially a latex balloon filled with ground coffee -- slips around hard objects like a beanbag, then contracts and hardens when a vacuum is applied, researchers at the University of Chicago, Cornell University in New York and iRobot Corp (IRBT.O) reported in the Proceedings of the National Academy of Science.
But when the vacuum is released and air rushes in, the hand loses its grip.
The team says the so-called “universal gripper” could be used on prosthetic limbs, to dismantle explosive devices, move potentially dangerous objects or as robotic arms in factories.
The design is based on the transition between two states -- a loose state and a jammed state, in which granules of coffee go from a fluid to a solid state.
“The ground coffee grains are like lots of small gears,” Hod Lipson, a Cornell associate professor of mechanical engineering and computer science, said in a statement.
“When they are not pressed together, they can roll over each other and flow. When they are pressed together just a little bit, the teeth interlock, and they become solid,” he said.
Many materials can do this, including rice or sand, but the team settled on ground coffee because it is lightweight.
They said the gripper worked well with many types of objects, including a raw egg and a coin -- two objects that can be tough for humans to manipulate.
The researchers and iRobot have filed for a patent on the technology.