The future of robotics may be centered on self-assembling "origami" robots that start out flat but can unfold themselves into 3D shapes to carry out their designed purposes, researchers say.

Such robots could cost less to build and transport and could also work in tighter spaces, they say.

The robots consist of layers of flat material, some of which are rigid while others are constructed from heat-shrinking polymers that can cause the robot to unfold when warmed up by heating elements embedded in the polymer.

Researchers at Harvard University, reporting their work in the August issue of the journal Science, say the engineering inspired by Japanese art of paper folding or origami could reduce the cost of creating complex devices and objects.

"I'm sure people have seen in examples of origami -- you can use folding to create fantastically complex structures," says research leader Robert Wood.

"But once the complexity of these things exceeds a threshold, folding them by hand becomes painstaking."

To get around this limitation, the Harvard researchers, working with colleagues at the Massachusetts Institute of Technology, set about creating a complex device that could unfold by itself.

That led to the design decision to use flat layers joined by hinges that could open and unfold under the control of the embedded heating elements.

Batteries and motors incorporated into the device when it was still flat could spring into action and provide walking motion once the origami robot was fully unfolded, they said.

The unfolding process takes about 4 minutes, they said, but that is bound to improve with more development.

Devices that can automatically unfold when needed could have many applications, Woods said, such as self-deploying structures to help in space exploration.

The researchers used computer programs that can push the boundaries of origami, quickly determining the required folding pattern to create almost any desired final result.

"Getting a robot to assemble itself autonomously and actually perform a function has been a milestone we've been chasing for many years," says Wood, who works in Harvard's School of Engineering and Applied Sciences.

The day may come when such robots can be inexpensively created using 3D printers and sold by stores, programmed to carry out simple household chores or maintenance work.

"You would be able to come in, describe what you need in fairly basic terms, and come back an hour later to get your robotic helper," Wood says.