Breaking away from conventional robots that perform only predefined functions once fabricated, researchers have developed a next-generation artificial muscle that can change its shape in real time, recover from damage, and even be reused.
Seoul National University College of Engineering announced that a joint research team led by Prof. Jeong-Yun Sun (Department of Materials Science and Engineering) and Prof. Ho-Young Kim (Department of Mechanical Engineering), with Yun Hyeok Lee, Seungwon Moon, and Min-gyu Lee as first and co-first authors, has developed a new type of dielectric elastomer actuator (DEA) using a phase-transitional ferrofluid (PTF) that behaves as a solid at room temperature but becomes fluid-like and highly flexible when exposed to external stimuli such as heat or magnetic fields.
The study was published on March 21 in Science Advances, a leading international journal published by the American Association for the Advancement of Science (AAAS).
Dielectric elastomer actuators (DEAs) are soft transducers that convert electrical energy into mechanical motion and are often referred to as artificial muscles because of their ability to move rapidly and precisely like human muscles.
Artificial muscles based on dielectric elastomers are soft and lightweight, and have increasingly been applied in daily lives and industrial settings, including haptic vibration components in smart and wearable devices, as well as soft robotic grippers capable of safely handling delicate objects such as fruits or fragile components.
However, once the electrode pattern is designed and printed, its shape becomes permanently fixed, meaning that such systems can only perform a single, predefined motion.
As a result, whenever a robot needs to grasp objects of different shapes or adapt to new environments, both industry and academia have been required to redesign and fabricate entirely new electrode patterns from scratch. This has led to significant manufacturing costs and inefficiencies, and has remained a major barrier to the commercialization of versatile, multifunctional soft robots.
To overcome these limitations, Lee et al. developed a next-generation soft gel actuator capable of dynamically reconfiguring electrode patterns in real time, performing new functions as needed, and recovering even after mechanical damage or electrical failure.
The newly developed phase-transitional ferrofluid (PTF) electrode can dynamically split and merge into three-dimensional configurations. Even after fabrication, its shape and position can be freely adjusted, significantly expanding the functional capabilities of soft robots beyond fixed, predesigned motions. In addition, the electrode's self-healing and recyclability enhance the sustainability of robotic systems.
A key achievement of this study lies in the seamless integration of advanced materials engineering, through the precise combination of nanoparticles and polymers, with a fully functional mechanical system. Materials engineering enabled the development of a stable yet flexible phase-transitional electrode, while mechanical engineering demonstrated how the material operates during actuation, reconfiguration, and recovery.
As a result, a single soft actuator can now perform entirely different roles depending on the situation, transforming conventional soft robots into adaptive systems capable of altering their functions in response to changing environments and tasks.
○ Key Features of the Phase-Transitional Ferrofluid (PTF) Electrode
1. Real-Time Functional Reconfiguration (Reconfiguration):
Even during operation of the artificial muscle, the electrode can be melted into a liquid state (sol) and repositioned using a magnetic field, or split into two or more parts. Beyond simple two-dimensional planar movement, it can be spatially partitioned in 3D architectures to perform different functions, or autonomously bridge severed circuits via 3D out-of-plane configurations, thereby achieving an advanced level of functional freedom. This enables a single robot to perform entirely different motions, such as bending and expansion, as if learning them in real time.
2. Self-Healing and Recovery Capability (Self-healing & Recovery):
The system remains functional even if the electrode is severed by sharp objects or if electrical breakdown occurs due to high voltage. By converting the electrode near the damaged region into a liquid state, the broken circuit can be reconnected, or the system can be reconfigured to bypass only the damaged area, thereby fully restoring the robot's functionality.
3. Environmentally Friendly Reusability (Recyclable):
After a device has completed its task or reached the end of its lifespan, the electrode alone can be extracted in liquid form, stored, and later injected into a new device for reuse. Lee et al. demonstrated that even after multiple reuse cycles, the system maintains a high recovery rate of approximately 91% along with consistent performance.
This research represents a transformative step toward ending the era of passive and disposable machines, introducing instead a new class of sustainable, adaptive systems capable of continuous regeneration and self-reconfiguration. The technology has broad potential applications, ranging from highly advanced artificial muscles capable of replicating complex, multi-degree-of-freedom human movements, to next-generation form-factor displays that can dynamically alter shape and information in real time, and smart robots that can repair themselves while operating in extreme industrial environments involving electrical failure or physical damage.
Furthermore, by enabling electrodes to be extracted and reused rather than discarding entire devices at the end of their lifespan, the study proposes a fundamentally new, environmentally sustainable resource circulation paradigm that could significantly impact future soft robotics and next-generation electronics industries.
Prof. Jeong-Yun Sun stated, "This study represents a breakthrough in transforming traditionally static and passive electrodes into 'living, programmable elements' through innovations in particle and polymer design. This self-healing and shape-reconfigurable electrode technology will serve as a key foundation for sustainable next-generation soft robotics."
Prof. Ho-Young Kim added, "From a mechanical engineering perspective, achieving high degrees of freedom in soft robots, similar to human muscles, requires structural flexibility. Through interdisciplinary integration with materials engineering, we demonstrated that a single robotic structure can generate virtually limitless modes of motion."
Yun Hyeok Lee, who received his PhD from SNU's Department of Materials Science and Engineering, is currently conducting postdoctoral research at the Massachusetts Institute of Technology (MIT), focusing on the development of new platform materials using nanoparticles, DNA, and polymers.
Seungwon Moon, a PhD candidate in the same department, is currently working on the development of high thermal conductivity polymer materials for semiconductor and electronic device applications.
Min-gyu Lee received his PhD from SNU and is now working at Samsung Electronics' Semiconductor Research Center, where he is involved in the development of next-generation high-bandwidth memory (HBM).
This research was conducted with support from the Ministry of Science and ICT and the National Research Foundation of Korea through the Mid-career Researcher Program, the Future Promising Fusion Technology Pioneer Program, and the Global Leader Grants.
□ Introduction to the SNU College of Engineering
Seoul National University (SNU) founded in 1946 is the first national university in South Korea. The College of Engineering at SNU has worked tirelessly to achieve its goal of 'fostering leaders for global industry and society.' In 12 departments, 323 internationally recognized full-time professors lead the development of cutting-edge technology in South Korea and serving as a driving force for international development.
