Smart Pebbles 2D Duplication
An MIT research group created tiny robots called "smart pebbles". Although individually these robots do not have a lot of intelligence, they can collaborate and function together in order to replicate simple objects as shown below.
The video below shows only a proof-of-concept made using current state of the art technology. It is possible to imagine that by shrinking the robots, more complex objects could be replicated and dissolved at will. "You don't need to carry all your tools with you," says one of the researchers, "just a bag of sand."
Via IEEE Spectrum