Use coffee grounds or sand to pick things up

From Science News.

The simple gripper is made of a bag of coffee grounds and a vacuum, though other grains such as couscous and sand also work, says study coauthor Eric Brown of the University of Chicago. To pick something up, the bag of loose grounds first melds around the object. Then as a vacuum sucks air out of the spaces between grains, the gripper stiffens, packing itself into a hard vise molded to the outline of the object. Reducing the bag’s starting volume by just a teeny amount — less than 1 percent of the total — was enough to make the gripper latch on, the team found.

This transition from fluidlike behavior (such as dry sand flowing out of a bucket) to solid (a hard-packed sand castle) is a physical process called “jamming.” Because the gripper’s bulb conforms to any shape evenly before the vacuum jams it, it’s extremely versatile. “Our goal was to pick up objects where you don’t know what you’re dealing with ahead of time,” Brown says.