A team of researchers from the Massachusetts Institute of Technology (MIT) and Harvard have created robots that are more than meets the eye – as soon as batteries are attached to them, they have the ability to fold themselves up and then crawl away.
The researchers challenged themselves to find a way to create a robot cheaply that wouldn't require expert assembly. After noticing that the Japanese art of origami is used to fold paper into complex shapes, they decided to imitate this design.
Their report is published in the 8 August issue of the journal Science.
"Getting a robot to assemble itself autonomously and actually perform a function has been a milestone we've been chasing for many years," said senior author Rob Wood, a Core Faculty member at the Wyss Institute for Biologically Inspired Engineering at Harvard University and the Charles River Professor of Engineering and Applied Sciences at Harvard's School of Engineering and Applied Sciences (SEAS).
"Folding allows you to avoid the 'nuts and bolts' assembly approaches typically used for robots or other complex electromechanical devices and it allows you to integrate components, for example electronics, sensors and actuators while flat."
To do this, the researchers decided to use five different layers of materials, all cut to digital specifications by a laser.
The robot consists of a layer of copper etched into an intricate network of electrical leads. That layer is sandwiched between two structural layers of paper, and the paper is covered by a shape-memory polymer that folds when heated.
The researchers added two motors powered by two batteries and a microprocessor to the robot, as well as hinges to each leg containing embedded circuits.
At first, the robot looks like a flat sheet of paper. When the microprocessor sends the command, the embedded circuits in the leg hinges produce heat, which triggers the sheet to fold by itself at specific angles, with the sharpest fold being 150 degrees.
When the hinges cool down four minutes later, the polystyrene hardens, making the robot stiff, and the microprocessor then signals the robot to crawl away, at the speed of one-tenth of a mile per hour.
"That's exciting from a geometry standpoint, because it lets us fold more things. Because we can do the sequencing, we have a lot more control. And it lets us make active folding structures. Instead of just self-assembly, you can then make it walk," said co-author Erik Demaine, an MIT professor of computer science and engineering.
"It's called a one-degree-of-freedom structure, in which you just need to turn one crank and the whole thing moves in the way that you want.
"You need to be able to do a single fold, ideally all the way to 180 degrees, in both directions, then the next level of challenge is to do what's called a cyclic fold, where you have a bunch of panels connected together in a cycle, and they can all fold simultaneously. That's demonstrated in one component of the system."
The researchers' long-term goal is to create a facility that everyone could access around the clock in their communities when they might have a need for robotic assistance, from sweeping the home to detecting gas leaks in the neighbourhood.
"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," said Wood.
Each robot costs $100 (£59) to make, but only $20 (£12) for the body without the motors, batteries, and microcontroller.