In a groundbreaking development for robotics and materials science, researchers in South Korea have engineered an artificial muscle capable of lifting nearly 4,000 times its own weight — a feat that could redefine the future of humanoid robots and soft robotics.
Led by Professor Hoon Eui Jeong from the Ulsan National Institute of Science and Technology (UNIST), the research team tackled one of the core challenges in artificial muscle design: achieving both strength and flexibility. As Jeong explained,
“This research overcomes the fundamental limitation where traditional artificial muscles are either highly stretchable but weak or strong but stiff. Our composite material can do both, opening the door to more versatile soft robots, wearable devices, and intuitive human-machine interfaces.”
At the heart of this breakthrough lies a “high-performance magnetic composite actuator”, a sophisticated combination of polymers and magnetic particles engineered to mimic the contraction and relaxation of biological muscles. One polymer’s stiffness can be adjusted, while magnetic microparticles embedded on its surface provide additional control and movement precision. This unique structure allows the artificial muscle to become stiff when lifting heavy loads and soft when contracting, just like human muscle tissue.
To accomplish this balance, the researchers used a dual cross-linking architecture. One network involves covalent bonds strong, stable chemical links while the other features reversible physical interactions that allow flexibility. Reinforced with NdFeB microparticles coated in octadecyltrichlorosilane, the structure achieves both durability and adaptability, effectively resolving the long-standing trade-off between stiffness and stretchability in synthetic muscles.
In testing, the artificial muscle weighing only 1.13 grams (0.04 ounces) demonstrated an incredible ability to lift 5 kilograms (11 pounds), equivalent to 4,400 times its own weight. It also achieved a strain of 86.4%, more than double that of human muscle (which typically contracts around 40%), and reached a work density of 1,150 kilojoules per cubic meter 30 times greater than natural muscle tissue.
To verify these results, the researchers performed a uniaxial tensile test, a standard method in materials science where a pulling force is applied until the sample fractures. This test allowed the team to precisely measure tensile strength and elongation, confirming the exceptional mechanical performance of their design.