When the volume of fluid within the sacs was adjusted using an electric pump, a tension is created to drive movement, a method which is safer than artificial muscles driven by highly pressurised fluids, they added.
The muscles, known as actuators, are built on a framework of metal coils or plastic sheets, and each muscle costs around $1 to make, said the report in the Proceedings of the National Academy of Sciences, a peer-reviewed U.S. journal. One 2.6 gram muscle is able to lift a 3 kilogram object, which is the same as a duck lifting a auto. "The next step is to take this system and develop it into a fully functional robot".
"This is like giving super powers to these robots", says the main author of the work of Daniela Rus, professor of electrical engineering and computer science at the Massachusetts Institute of Technology (MIT).
They are capable of lifting loads many times their own weight, including a auto wheel which was lifted 20cm within 30 seconds, and a 1kg weight.
"Artificial muscle-like actuators are one of the most important grand challenges in all of engineering", said co-author Rob Wood, professor of engineering and applied sciences at Harvard University.
"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", MIT postdoc and paper lead Shuguang Li explained.
This allows the muscles to be very compact and simple, and thus more appropriate for mobile or body-mounted systems that can not accommodate large or heavy machinery.
The possible uses include habitat spatial scalable on March, surgical devices, miniature, exoskeletons laptops, exploration vehicles in deep water sea or architectures transformable.
It can be made of a range of materials, and to test it in various forms the researchers used metal springs, packing foam and plastic sheets, among other things.
They created "muscles that can contract down to 10 per cent 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", said the report. "We have built them at sizes ranging from a few millimeters up to a meter, and their performance holds up across the board". They even made a muscle out of a water-soluble polymer, which means the technology could be used in natural setting with minimal environmental impact.
"The possibilities really are limitless", Rus said. "We were very surprised by how strong the muscles were".