"We started with a flat sheet, to which they added two motors, two batteries and a microcontroller - which acts like the robot's brain," Felton informed.

The sheet also included hinges that were programmed to fold at specific angles.

Each hinge contained embedded circuits that produce heat on command from the microcontroller. The heat triggers the composite to self-fold in a series of steps.

The entire event consumed about the same amount of energy in one AA alkaline battery.

"The current robot operates on a timer, waiting about 10 seconds after the batteries are installed to begin folding," Felton noted.

"Getting a robot to assemble itself autonomously and actually perform a function has been a milestone we have been chasing for many years," said senior author Rob Wood from the Wyss Institute for Biologically-Inspired Engineering at Harvard University.

Each robot cost about $100 but only $20 for the body without the motors, batteries and microcontroller.

The findings were described in the journal Science.

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