To find the right material for the gripper, the researchers experimented with several things, including rice, couscous, and even ground-up tires. However, ground coffee beans provided the precise combination of light weight as well as good interlocking ability.Noting that “ground coffee grains are like lots of small gears,” study co-author Hod Lipson, a mechanical engineer at the University of Chicago, 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.”
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