Artificial muscles that can lift 12,600 times their own weight

New York: Using carbon fiber, a very strong light-weight material which is readily commercially available, researchers have designed artificial muscles capable of lifting up to 12,600 times their own weight.

"The range of applications of these low cost and light-weight artificial muscles is really wide and involves different fields such as robotics, prosthetics, orthotics, and human assistive devices," said one of the researchers Caterina Lamuta from Beckman Institute for Advanced Science and Technology in Illinois. 

The new muscles, detailed in the journal Smart Materials and Structures, are made from carbon fiber-reinforced siloxane rubber and have a coiled geometry.

These muscles are capable of not only lifting up to 12,600 times their own weight, but also supporting up to 60 MPa of mechanical stress, providing tensile strokes higher than 25 percent and specific work of up to 758 J/kg (joule/kg), the study said. 

This amount is 18 times more than the specific work natural muscles are capable of producing, the researchers added. 

When electrically actuated, the carbon fiber-based artificial muscles showed excellent performance without requiring a high input voltage.

The authors showed how a 0.4 mm diameter muscle bundle was able to lift half a gallon of water by 1.4 inches with only 0.172 V/cm applied voltage.

The artificial muscles themselves are coils comprised of commercial carbon fibers and polydimethylsiloxane (PDMS). 

A carbon fibres tow is initially dipped into uncured PDMS diluted with hexane and then twisted with a simple drill to create a yarn with a homogeneous shape and a constant radius. 

After the curing of the PDMS, the straight composite yarn is highly twisted until it is fully coiled.

"Coiled muscles were invented recently using nylon threads," said Sameh Tawfick, Assistant Professor at University of Illinois Urbana Champaign in the US.

"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," Tawfick explained.