Even if you exercise 24/7, you can only tone and strengthen your muscles to some extent. Artificial muscles overtook their natural counterparts a long time ago. Researchers from the Department of Mechanical Science and Engineering at the University of Illinois have developed an artificial muscle made of carbon fiber and rubber that can lift over 12,000 times its own weight.
The Illinois team set out with the goal to make coiled artificial muscles. This design is stronger and more practical. They chose carbon fiber as it is very strong and also lightweight. The carbon fiber was mixed with polydimethylsiloxane (PDMS) rubber to make it more deformable and it was twisted into a coiled shape.
“Coiled muscles were invented recently using nylon threads,” says Sameh Tawfick, an author of the study. “They can exert large actuation strokes, which make them incredibly useful for applications in human assistive devices: if only they could be made much stronger. To use carbon fibers, we had to understand the mechanism of contraction of coiled muscles. Once we uncovered the theory, we learned how to transform carbon fibers into ultra-strong muscles. We simply filled carbon fiber tows with the suitable type of silicone rubber, and their performance was impressive, precisely what we had aimed for.”
The muscles can be flexed by applying a small electric current to the ends. This heats up the silicone rubber and pushes the carbon fibers apart expanding the diameter and contracting the length. This pulls up the load attached to the bottom. This contraction can also be brought about by delivering liquid hexane to the coiled muscle.
The team found the artificial muscles to be very strong during the tests. An artificial muscle bundle measuring just 0.4 mm across was able to lift a half-gallon of water by 1.4 in (3.6 cm), with an applied voltage of only 0.172 volts per cm. It was able to lift up to 12,600 times its own weight, support up to 60 megapascals of mechanical stress, was capable of tensile strokes over 25 percent, and produced specific work of up to 758 joules per kg.
“The range of applications of these low cost and lightweight artificial muscles is really wide and involves different fields such as robotics, prosthetics, orthotics, and human assistive devices,” says Caterina Lamuta, an author of the study. “The mathematical model we proposed is a useful design tool to tailor the performance of coiled artificial muscles according to the different applications. Furthermore, the model provides a clear understanding of all the parameters that play an important role in the actuation mechanism, and this encourages future research works toward the development of new typologies of fiber-reinforced coiled muscles with enhanced properties.”
You can see the artificial muscles in action in the video below: