Soft robots have long promised machines that move more like living creatures than factory arms, but their “muscles” have struggled to be both powerful and supple at the same time. A new magnetic polymer now pushes past that trade-off, delivering artificial muscles that can stretch dramatically while packing record levels of mechanical work into each contraction. The advance builds on a fast-moving wave of research that is redefining how magnetic materials, polymers, and phase-change chemistry can be combined to give robots strength, agility, and even variable stiffness.
Instead of relying on bulky motors or fragile pneumatic bladders, these magnetic muscles use carefully engineered polymers loaded with responsive particles to turn magnetic fields into motion. By pairing dual cross-linked networks with ferromagnetic or magnetic microparticles, researchers are closing the gap with biological tissue and, in some cases, surpassing what human muscle can do on raw strength alone.
How a dual cross-linked magnetic polymer breaks the old trade-offs
The core breakthrough in the latest work is a dual cross-linked magnetic polymer that behaves like a stretchy rubber band until a magnetic field snaps it into action. Researchers designed this material so that one polymer network provides elasticity while a second, sacrificial network dissipates energy and prevents catastrophic tearing, which lets the artificial muscle reach very high strains without failing. By embedding magnetic particles into this dual network, the team created a soft actuator that can be driven remotely and still deliver a record work density for a polymer-based muscle, a performance level detailed by Researchers.
What makes this polymer particularly notable is that it does not force engineers to choose between force and flexibility. Earlier soft magnetic actuators often delivered impressive strain but modest force, or vice versa, limiting their usefulness in tasks that require both reach and grip. In this design, the dual cross-linking strategy lets the material stretch significantly while still transmitting large magnetic stresses through the embedded particles, which is why the reported work density sets a new benchmark for soft artificial muscles. The same group describes how this New magnetic polymer overcomes a long-standing barrier in artificial muscle performance, opening the door to compact, high-torque soft actuators.
From lab material to lifting machine: the South Korea connection
The dual-network concept is not emerging in isolation, and its potential becomes clearer when viewed alongside a striking demonstration from South Korea. A scientific team in South Korea developed an artificial muscle built from a dual polymer network combined with magnetic components, translating the material idea into a device that can lift extraordinary loads. That actuator, which uses polymers and magnetic microparticles, was shown to raise objects up to 4,000 times its own weight, a figure that puts it far beyond the relative strength of human muscle and illustrates how magnetic composites can concentrate force.
The same South Korean work emphasizes that the new material, developed in South Korea, mimics key aspects of biological human muscle tissue while still exploiting the advantages of synthetic polymers and magnetic control. By tuning the polymer chemistry and particle loading, the researchers achieved a balance of compliance and strength that lets the actuator bend and twist like a muscle yet behave like a high-ratio gearbox when a magnetic field is applied. That combination of biomimicry and raw lifting capacity is a preview of what the newer dual cross-linked magnetic polymers could deliver once they are integrated into full robotic systems.
Record work density and variable stiffness reshape soft robotics
Behind the headline-grabbing lifting feats is a quieter but equally important metric, work density, which measures how much mechanical work a muscle can do per unit volume. Recent studies on Soft magnetic artificial muscles report some of the highest work densities yet achieved for soft actuators, confirming that magnetic composites can compete with, and in some regimes surpass, traditional pneumatic or thermal systems. High work density matters because it allows designers to shrink actuators without sacrificing capability, which is crucial for humanoid robots, wearable devices, and compact medical tools that cannot afford bulky hardware.
At the same time, researchers affiliated with UNIST have shown that artificial muscles can transition from soft and flexible to rigid and load bearing, then back again, while still lifting up to 4,000 times their own weight. That variable stiffness behavior, achieved in a magnetic composite muscle, lets a robot arm remain compliant when interacting with people or delicate objects, then lock into a stiffer configuration when it needs to support heavy loads. It is a capability that biological systems achieve through co-contraction and tendon tension, and it is now being approximated in polymer-based actuators.
Magnetic muscles move from lab demos to practical loads
The leap from tabletop experiments to practical lifting is already underway. One soft magnetic muscle design presented as a reconfigurable and adaptable actuator can lift 1,000 times its own weight, outperforming both biological muscle and many existing artificial muscles on a strength-to-weight basis, according to Nov. That device uses a soft magnetic composite that can be reshaped and reprogrammed, allowing the same material to serve as a gripper, a linear actuator, or a bending joint depending on how it is magnetized and mounted.
Another line of work focuses on multifunctional magnetic muscles that integrate a phase-change polymer with ferromagnetic particles, enabling both actuation and locking behavior in a single structure. In this configuration, the phase-change component lets the muscle soften or harden with temperature, while the magnetic particles provide the driving force under a field, a combination described in detail in Sep. That approach gives engineers a way to build joints that can move freely, then lock in place without continuous power, which is attractive for energy-efficient robots and exoskeletons.
Humanoid robots and prosthetics stand to gain first
The most dramatic showcase of magnetic muscle potential comes from work at the Ulsan National Institute, where researchers built an artificial muscle that lets humanoid robots lift 4,000 times their own weight. That actuator, described as a high-performance magnetic composite, uses a complex combination of polymers, magnetic particles, and surface treatments to convert modest magnetic fields into enormous mechanical advantage, enough to move from lifting a smartphone to hoisting a sports bike without changing the underlying mechanism, as reported in Oct.
Those same design principles are now converging with the dual cross-linked magnetic polymer work, which is documented in detail by Sto and colleagues, and by a follow-up analysis of the Researchers who developed the material. As these materials mature, I expect humanoid robots and advanced prosthetic limbs to be among the first beneficiaries, since they demand actuators that are compact, quiet, and capable of both gentle interaction and serious lifting. The ability to tune stiffness, reconfigure magnetization patterns, and exploit high work density in a soft package could finally give roboticists a muscle analogue that is not just inspired by biology but competitive with it on performance.
