U.S. researchers said Monday they have created origami-inspired artificial muscles that allow soft to lift objects that are up to 1,000 times their own weight using only air or water pressure.
These muscles consist of an inner "skeleton" that can be made of various materials, such as a metal coil or a sheet of plastic folded into a certain pattern, surrounded by air or fluid and sealed inside a plastic or textile bag that serves as the "skin," said the study in the U.S. journal Proceedings of the National Academy of Sciences.
A vacuum applied to the inside of the bag initiates the muscle's movement by causing the skin to collapse onto the skeleton, creating tension that drives the motion.
"We were very surprised by how strong the actuators (also known as muscles) were," said Daniela Rus, professor of electrical engineering and computer science at the Massachusetts Institute of Technology and one of the senior authors of the paper.
"We expected they' d have a higher maximum functional weight than ordinary soft robots, but we didn't expect a thousand-fold increase. It's like giving these robots superpowers," Rus said.
First author Shuguang Li, a Postdoctoral Fellow at the Wyss Institute at Harvard University and MIT's Computer Science and Artificial Intelligence Laboratory (CSAIL) said one key aspect of these muscles is that they're programmable, "in the sense that designing how the skeleton folds defines how the whole structure moves."
"You essentially get that motion for free, without the need for a control system," said Li. "This approach allows the muscles to be very compact and simple, and thus more appropriate for mobile or body-mounted systems."
The team constructed dozens of muscles using materials ranging from metal springs to packing foam to sheets of plastic, and experimented with different skeleton shapes to create muscles that can contract down to 10 percent of their original size, lift a delicate flower off the ground, and twist into a coil, all simply by sucking the air out of them.
Not only can the artificial muscles move in many ways, they do so with impressive resilience.
According to the researchers, these muscles can generate about six times more force per unit area than mammalian skeletal muscle can, and are also incredibly lightweight.
For example, a 2.6-gram muscle can lift a 3-kilogram object, which is the equivalent of a mallard duck lifting a car.
Additionally, a single muscle can be constructed within 10 minutes using materials that cost less than one U.S. dollars, making them cheap and easy to test and iterate.
The muscles can be used in numerous applications at multiple scales, such as miniature surgical devices, wearable robotic exoskeletons, transformable architecture, deep-sea manipulators for research or construction, and large deployable structures for space exploration, the study said.
The team was even able to construct the muscles out of the water-soluble polymer PVA, which opens the possibility of robots that can perform tasks in natural settings with minimal environmental impact, as well as ingestible robots that move to the proper place in the body and then dissolve to release a drug.
"The possibilities really are limitless. But the very next thing I would like to build with these muscles is an elephant robot with a trunk that can manipulate the world in ways that are as flexible and powerful as you see in real elephants," Rus said.