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Artificial muscles. Changing the future of robots

Soft #robotics has made leaps and bounds over the last #decade as researchers around the world have experimented with different #materials and designs to allow once #rigid, jerky machines to bend and flex in ways that #mimic and can interact more naturally with living #organisms. However, increased #flexibility and dexterity has a trade-off of reduced #strength, as softer materials are generally not as strong or resilient as inflexible ones, which #limits their use.

Not only researchers at the Wyss Institute at #Harvard University and MIT’s Computer #Science and Artificial Intelligence #Laboratory (CSAIL) have created origami-inspired artificial #muscles that add strength to soft robots, allowing them to lift objects that are up to 1,000 times their own #weight using only #air or #water #pressure, giving much-needed strength to soft #robots.

“We were very surprised by how #strong the #actuators [aka, “muscles”] were. 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,” says Daniela Rus, Ph.D., the Andrew and Erna Viterbi #Professor of Electrical Engineering and #Computer #Science at MIT and one of the #senior authors of the paper.

Origami-inspired #artificial muscles are capable of lifting up to 1,000 times their own #weight, simply by applying #air or #water pressure.
Credit: #Shuguang Li / Wyss Institute at #Harvard #University

“Artificial muscle-like #actuators are one of the most important grand #challenges in all of engineering,” adds  Rob #Wood, Ph.D., corresponding author of the paper and #Founding #Core Faculty member of the #Wyss Institute, who is also the Charles River Professor of Engineering and Applied #Sciences at Harvard’s John A. #Paulson School of Engineering and Applied Sciences (SEAS). “Now that we have created #actuators with properties similar to natural #muscle, we can imagine building almost any robot for almost any task.”

Each #artificial muscle consists 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.” 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. Incredibly, no other #power source or human input is required to direct the muscle’s #movement; it is determined entirely by the #shape and composition of the #skeleton.

“One of the key #aspects 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,” says first author #Shuguang Li, Ph.D., a Postdoctoral #Fellow at the Wyss Institute and MIT #CSAIL. This approach allows the #muscles to be very compact and simple, and thus more appropriate for #mobile or #body-mounted systems that cannot accommodate large or heavy #machinery.

Artificial #muscle-like #actuators are one of the most important grand challenges in all of #engineering.

ROBERT WOOD

“When creating #robots, one always has to ask, ‘Where is the #intelligence – is it in the body, or in the brain?’” says #Rus. “Incorporating #intelligence into the body (via specific folding patterns, in the case of our actuators) has the #potential to simplify the algorithms needed to direct the robot to achieve its #goal. All these #actuators have the same simple on/off switch, which their #bodies then translate into a broad range of motions.”

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% 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.

The structural #geometry of artificial muscle s#keleton determines the muscle’s motion. Credit: Shuguang Li / #Wyss Institute at #Harvard University

Not only can the #artificial muscles move in many ways, they do so with impressive #resilience. They can generate about six times more #force per unit area than #mammalian skeletal muscle can, and are also incredibly #lightweight; 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 ten minutes using materials that cost less than $1, making them cheap and easy to #test and #iterate.#

These #muscles can be powered by a #vacuum, a feature that makes them safer than most of the other artificial #muscles currently being tested. “A lot of the #applications of soft #robots are human-centric, so of course it’s important to think about #safety,” says Daniel Vogt, M.S., co-author of the paper and #Research Engineer at the Wyss #Institute. “Vacuum-based #muscles have a lower risk of rupture, failure, and #damage, and they don’t expand when they’re operating, so you can integrate them into closer-fitting #robots on the human #body.”

“In addition to their #muscle-like properties, these soft actuators are highly #scalable. We have built them at sizes ranging from a few #millimeters up to a meter, and their performance holds up across the board,” Wood says. This #feature means that 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 #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 says.

“The actuators developed through this #collaboration between the Wood #laboratory at Harvard and Rus group at MIT exemplify the Wyss’ approach of taking inspiration from #nature without being limited by its conventions, which can result in systems that not only #imitate nature, but surpass it,” says the Wyss Institute’s Founding Director Donald #Ingber, M.D., Ph.D., who is also the Judah #Folkman Professor of Vascular #Biology at HMS and the Vascular Biology Program at Boston Children’s #Hospital, as well as Professor of #Bioengineering at SEAS.

The research was funded by the #Defense Advanced Research Projects #Agency (DARPA), the National Science #Foundation (NSF), and the Wyss Institute for #Biologically Inspired #´Engineering.

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