Soft robotics has been a promising field of research for years, but these squidgy and flexible creations have been delayed by the absence of one important feature: strength. Now, scientists at MIT CSAIL and the Wyss Institute at Harvard have devised a way to give soft robots some power by endowing them with rigid origami skeletons.
In an article 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 collapsible origami structure that functions like the skeleton. When the pressure inside the bag is reduced by an electric pump, the entire structure collapses and contracts, as do 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 a lot of potential, but so far, one of the limitations has been the payload," says Professor Daniela Rus, director of CSAIL and lead author of article The Verge . "[They’re] very safe, very soft, but not good for lifting heavy objects." This new approach allows us to make strong and soft robots. "
Muscles have a number of potential uses, more obviously in warehouses and logistics operations, where they can safely handle fragile and delicate objects such as fruit. They are also suitable for collecting objects with unusual shapes, a challenge so persistent in robotics that Amazon makes an annual competition to try to solve it.
Some researchers use grabbers as suction cups to handle irregular shapes, while others apply AI to try to calculate the best way to capture their goal. Soft robots, however, can simply reach out and grasp, trusting that the deformable shape of their grip will be molded around the target. In this sense, they are similar to human hands, says Rus, who can "wrap the object, no matter what form it is". The new origami skeleton would make these softer grippers more useful by allowing them to handle heavier objects.
However, the new muscles have their drawbacks. The most important thing is that they are not as easily controlled or reprogrammable as traditional robots. The direction in which they move is completely dictated by their internal structure and once created, it can not be changed. "You make up different patterns of movement within the skeleton that define how the system as a whole moves," says Rus. In other words, if you double the internal structure of origami as this or as can cause it to collapse in the direction you want.
However, this is not as limiting as you might think. We can use algorithms to find origami patterns that fold in almost infinite ways, so that these muscles can perform even complicated movements, such as spinning. (This is potentially useful in badembly lines.) However, this still means that these artificial muscles are not as dynamic or adaptable as more traditional industrial robots.
They balance it with other benefits. To begin with, because the way the muscle moves is defined by its structure, you do not need a complicated electronic control system to tell you what to do, just something to turn it on or off. Muscles can also be built with a variety of cheap and lightweight materials, which means they can be manufactured quickly and easily repaired. This means that they could be used to build inexpensive exoskeletons that would bind our bodies to increase our own strength.
For Rus, however, the real magic is the ease with which these muscles can be combined and redesigned to create new ways 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, he has used origami to program movement in all kinds of creations, from small robots with flat exoskeletons to ingestible machines that develop in the stomach. "Origami has this beautiful universality," says Rus.
But because of their strength and the ease with which they can be attached, these artificial muscles could have the greatest potential. "We have demonstrated a combination of four muscles that forms an arm with a clamp that can lift a tire," says Rus. "If we put a joint there and add another arm, which is quite easy to do, we could not just lift the tire, but move it and place it anywhere."
And what's next for the team? Building a soft robot elephant trunk that is "as flexible and powerful" as that of a real elephant. "He's as big as a human person," says Rus.