Robots can already find objects in plain sight, but asking them to go beneath the surface is tougher — they'll have to operate by touch if they squirm through sand, and wireless tech like radar only produces a indistinct view of what's below. That might not be as much of a challenge for long, though, as MIT researchers have built a robot "Digger Finger" (really, a probe) that can sift through granular material like sand to find objects by feel.
The machine is an upgraded version of an earlier tactile sensor that combined a clear gel with a reflective membrane that bent in contact with objects. LEDs shine through the gel on to the membrane, and a camera captures the reflection patterns to help computer vision develop the 3D shape of objects below. It effectively knows the difference between the sand it's digging through and an object worth retrieving.
The new robot is slimmer and simpler, and moves about thanks to a robot arm as well as vibration that helps it wiggle through grains. It can twist and otherwise move around to get the true sense of an item's dimensions.
There's a lot of necessary refinement left, including adjusting the movement to reflect different substances. However, the scientists already envision a number of practical uses. This could be used to find land mines without endangering people, or check data cables for cuts. We'd add that it could also be helpful for large-scale archaeological digs, or rescue operations where someone might be trapped by an avalanche or landslide. Don't be surprised if this translates to real-world robots before long.