Soft robotics has been a promising field of research for years, but these squidgy and flexible creations have been held back by the absence of one important characteristic: strength. Now, scientists from MIT CSAIL and Harvard’s Wyss Institute have come up with a way to give soft robots some power — by outfitting them with rigid origami skeletons.
In a paper published today in the journal PNAS, researchers describe a new type of soft artificial muscle that could be used to build soft robots. Each muscle consists of a sealed bag filled with air or fluid, containing a folding origami structure that functions as the skeleton. When the pressure inside the bag is reduced using an electric pump, the whole structure collapses and contracts, just like the muscles in your arm or leg. It may not sound like a recipe for strength, but these artificial muscles are much stronger than their human counterparts, capable of lifting 1,000 times their own weight.
“Soft robots have so much potential, but up until now, one of the limitations has been payloads,” Professor Daniela Rus, CSAIL director and lead author of the paper, tells The Verge. “[They’re] very safe, very gentle, but not good for lifting heavy objects. This new approach allows us to make strong and soft robots.”
The muscles have a number of potential uses, most obviously within warehouses and logistic operations, where they can safely handle breakable and delicate objects like fruit. They’re also well-suited for picking up objects with unusual shapes — a challenge so persistent in the robotics that Amazon holds an annual competition to try and solve it.
Some researchers use grabbers like suction cups to handle irregular shapes, while others apply AI to try and calculate the best way to grasp their target. Soft robots, though, can simply reach out and grab, trusting that the deformable shape of their gripper will mold around the target. In this regard they’re similar to human hands, says Rus, which can “wrap around the object, no matter what shape it is.” The new origami skeleton would make such soft grabbers more useful, by allowing them to handle weightier objects.
The new muscles have their drawbacks, though. The biggest being that they’re not as easily controlled or as reprogrammable as traditional robots. The direction they move in is entirely dictated by their inner structure and once created, can’t be changed. “You compose distinct movement patterns inside the skeleton that define how the system as a whole moves,” says Rus. In other words, if you fold the inner origami structure like this or like that, you can get it to collapse in any direction you like.
This isn’t as limiting as you might think, though. We can use algorithms to find origami patterns that fold in near-infinite ways, so that these muscles can carry out even complicated motions, like twisting. (This being potentially useful in assembly lines.) However, this still means these artificial muscles aren’t as dynamic or adaptable as more traditional industrial robots.
They balance this with other benefits. For a start, because the way the muscle moves is defined by its structure, it doesn’t need a complicated electronic control system to tell it what to do — just something to turn it on or off. The muscles can also be built out of a range of cheap, lightweight materials, meaning they can be quickly fabricated and easily repaired. This means they could be used to build inexpensive exoskeletons which we would strap onto our body to increase our own strength.
For Rus, though, the real magic is how easily these muscles can be combined and redesigned to create new forms of lifting, pushing, and pulling machines. “I started working with origami many years ago because I was interested in making modular robots that have programmable properties; I wanted to create programmable matter,” she says. Since then, she’s used origami to program movement into all sorts of creations — from tiny robots with flat-pack exoskeletons to ingestible machines that unfold in your stomach. “Origami has this beautiful universality,” says Rus.
But because of their strength and the ease with which they can be joined together, these artificial muscles might have the most potential. “We’ve shown a combination of four muscles that forms an arm with a gripper that can pick up a tire,” says Rus. “If we put a joint there and added another arm, which is quite easily done, we would be able to not just lift up the tire, but move it and place it anywhere.”
And what’s next for the team? Building a soft robot elephant trunk that’s “as flexible and powerful” as a real elephant’s. “It’s as big as a human person,” says Rus.