Seeking to identify objects buried in granular material — sand, gravel, and other types of loosely packed particles — isn’t a brand new quest. Previously, researchers have used technologies that sense the subterranean from above, such as Ground Penetrating Radar or ultrasonic vibrations. But these techniques provide only a hazy view of submerged objects. They might struggle to differentiate rock from bone, for example.

“So, the idea is to make a finger that has a good sense of touch and can distinguish between the various things it’s feeling,” says [Edward Adelson, the John and Dorothy Wilson Professor of Vision Science in CSAIL]. “That would be helpful if you’re trying to find and disable buried bombs, for example.” Making that idea a reality meant clearing a number of hurdles...

Adelson says the Digger Finger is part of a program extending the domains in which robotic touch can be used. Humans use their fingers amidst complex environments, whether fishing for a key in a pants pocket or feeling for a tumor during surgery. “As we get better at artificial touch, we want to be able to use it in situations when you’re surrounded by all kinds of distracting information,” says Adelson. “We want to be able to distinguish between the stuff that’s important and the stuff that’s not.”

(Via Robohub.)

Golden Age science fiction author Ray Cummings described sensitive robot fingers in his 1931 story The Exile of Time:

We had gone no more than a hundred feet or so when Migul [the robot] slowed our pace, and began to walk stooped over, with one of its abnormally long arms held close to the ground. The fingers were stiffly outstretched and barely skimmed the floor surface of the tunnel. As we passed through a spot of light I saw that Migul had extended from each of the fingertips an inch-long filament of wire, like finger nails.

Tugh's trail!... Migul's fingers with the extended filaments were feeling it. What strange sensitivity! What an amazing development of science was manifested in every move and act and word of this Robot!

The Robot's voice was a furtive sepulchral whisper that filled me with awe.

"He passed here an hour or two ago, perhaps. The vibrations are fading out. But it was Tugh. Well do I know him. Put your hand down. Feel the vibrations?"

"I cannot. My fingers are not that sensitive, Migul."

A faint contempt was in the Robot's tone. "I forgot that you are a man." Then it straightened, and the extended filaments slid back into its fingers...
(Read more about Ray Cummings super-sensitive robot fingers)