It might not look like much, but the new EcoBot II from Bristol is the closest thing yet to a completely self-sustaining robot. It eats flies. Flies which as of yet must (essentially) be spoon-fed to it—but the future promises brighter things, if not more pleasant smelling things; hopes for the EcoBot II being able to sustain itself without human intervention are pinned on its ability to attract flies, a feat that the robot would most likely achieve through sewage.
Previous attempts at an autonomous robot have included the “Slugbot” and “Chew-Chew”—the former designed, as you might suspect, to catch and digest the wily feral slug*, and the latter made to live off of sugar cubes (not a terribly viable alternative in the field of robots intended to be totally self-sufficient).
Progress marches onward.
(via NewScientist: “Self-sustaining killer robot creates a stink,” by Duncan Graham-Rowe [September 9, 2004])
Note:
* From the official Slugbot page:
“Apart from their relative ease of capture (compared to zebras), slugs were chosen because they are a major pest, are reasonably plentiful, have no hard shell or skeleton, and are reasonably large. It is also more technologically interesting to catch mobile prey rather than just grazing on plants.”