While the human hand can pick up, move and place objects easily, developing a robot to perform similar functions is challenging.
But to do just just that, researchers from Cornell University, University of Chicago and iRobot bypassed traditional designs based around the human hand and fingers, and created a versatile gripper using ground coffee and a latex balloon.
Hod Lipson, Cornell associate professor of mechanical engineering and computer science, said that the device has been named a ’universal gripper’, as it conforms to the object it’s grabbing rather than being designed for particular objects.
In use, a balloon filled with ground coffee is 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.
Heinrich Jaeger, a physicist at the University of Chicago, said that coffee is an example of a particulate material, which is characterised by large aggregates of individually solid particles. Particulate materials have a so-called jamming transition, which turns their behaviour from fluid-like to solid-like when the particles can no longer slide past each other.
Prototypes of the gripper were built and tested by Lipson and Cornell graduate student John Amend, as well as at iRobot.
As for the right particulate material, anything that can jam will work in principle and early prototypes involved rice, couscous and even ground-up tyres. The researchers settled on coffee because it is light but also jams well. Sand did better on jamming but was prohibitively heavy.
What sets the jamming-based gripper apart is its good performance with almost any object, including an egg or a coin − both notoriously difficult for traditional robotic grippers.
The project was supported by the US Defense Advanced Research Projects Agency.