For years, robotics engineers have worked on creating robot hands that can grip like the real thing. But it turns out that all they needed was some ground coffee and a party balloon.
The 'universal gripper' has almost unlimited applications, says Hod Lipson, Cornell associate professor of mechanical engineering and computer science.
The military could use it to dismantle explosive devices or to move potentially dangerous objects, and it could also be incorporated into robotic arms in factories and prosthetic limbs; it could even form the feet of a robot that could walk on walls.
"This is one of the closest things we've ever done that could be on the market tomorrow," Lipson said.
The design is about as simple as it gets. An ordinary party balloon is filled with ground coffee and attached to a robotic arm. The coffee-filled balloon presses down and deforms around the desired object, and then a vacuum sucks the air out of the balloon, solidifying its grip.
When the vacuum is released, the balloon becomes soft again, and the gripper lets go.
"The ground coffee grains are like lots of small gears," Lipson said. "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."
Many materials can be driven into this state, says the team. Early prototypes used rice, couscous and even ground-up tires. The team settled on coffee because it's light but also jams well; while sand did better on jamming, it was prohibitively heavy.
Coffee gave good performance with almost any object, says the team, including a raw egg or a coin – both notoriously difficult for traditional robotic grippers.
"What is particularly neat with the gripper is that here we have a case where a new concept in basic science provided a fresh perspective in a very different area – robotics – and then opened the door to applications none of us had originally thought about," said Heinrich Jaeger of the University of Chicago.