Robotic Hands Grip Without Fingers

sciencehabit writes "Physicists have designed a robotic hand that doesn't have fingers, yet can still serve drinks and draw pictures. The hand is a thin, rubber sack filled with coffee grains or small glass spheres. When it comes into contact with an object, a small pipe sucks air from the sack, causing it to contract and mold to the object's shape. As long as the gripper can fold about one-fourth of the object's surface, it can pick up just about any shape thrown in its path. The article includes a video of the hand in action."

Vac man?

[Geoffrey.landis]

Vac man [io9.com]! Is that you?

Re:It's a vacuum picker

[nickersonm]

It's not actually a vacuum picker: the gripping comes mostly from the change between unpacked and tightly packed granules inside the bag, somewhat like a non-Newtonian fluid. The idea is that the bag forms around an edge or partial circumference and then tightens enough to pick it up. The original paper's abstract [pnas.org] describes it better than the sciencemag article about it:

Individual fingers are replaced by a single mass of granular material that, when pressed onto a target object, flows around it and conforms to its shape. Upon application of a vacuum the granular material contracts and hardens quickly to pinch and hold the object without requiring sensory feedback. We find that volume changes of less than 0.5% suffice to grip objects reliably and hold them with forces exceeding many times their weight. We show that the operating principle is the ability of granular materials to transition between an unjammed, deformable state and a jammed state with solid-like rigidity.

There is sometimes an additional suction force assisting the gripper, but this is a suction-cup type action, not a vacuum pump action. The involved forces, from page two of the paper:

We find that this strength is due to three mechanisms, all controlled by jamming, that can contribute to the gripping process: geometric constraints from interlocking between gripper and object surfaces, static friction from normal stresses at contact, and an additional suction effect, if the gripper membrane can seal off a portion of the object’s surface.

Re:Lost an arm?

[gagol]

One fundraiser invited me for dinner some time ago. He had no hands, only two hooks and he was capable of cooking and baking and doing basically everything I could do. His cooking was better then mine though.