The new light-responsive springs outperform mammalian muscles (Representational image).
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A Korean research team has created a light-driven artificial muscle that functions independently underwater, advancing the future of soft robotics.
The system, developed by the Korea Research Institute of Chemical Technology (KRICT), uses azobenzene-functionalized semicrystalline liquid crystal elastomers (AC-LCEs) that activate when exposed to light.
The new light-responsive springs deliver triple the actuation stroke and double the work capacity of current photochemical actuators.
Surpassing mammalian muscles in performance, they enable precise, programmable motion control underwater, marking a major advancement in soft robotics and expanding possibilities for aquatic applications using light-powered artificial muscles.
Photonic muscle breakthrough
Underwater operation poses significant challenges for traditional soft robotic actuators, which typically rely on electricity, heat, or pressurized fluids. These systems involve complex components like batteries, motors, wires, or pumps that are difficult to waterproof and maintain in submerged conditions.
Photothermal materials have been proposed as an alternative, but their effectiveness underwater is limited. This is due to rapid heat dissipation from the surrounding water, which interferes with their ability to sustain shape changes. Similarly, existing photochemical actuators have shown only basic bending motions, as their molecular-level changes are restricted to surface layers.
Designing structures and “latch-mode” actuation of artificial muscles to control robotic systems.
To address these limitations, the Korean research team developed advanced AC-LCEs with enhanced stiffness and precisely controlled internal structures. By embedding azobenzene molecules into a specially designed liquid crystal elastomer, the researchers created materials that can contract or expand when exposed to ultraviolet or visible light, respectively.
Unlike most thermal systems, which lose their shape once the stimulus is removed, these AC-LCEs can retain their deformed shape temporarily. This allows for a latch-like locking mechanism that enables programmable, sequential, and spatially controlled motion.
According to the team, the breakthrough provides a robust solution for underwater actuation, opening new possibilities for the next generation of soft, light-powered aquatic robots.
Next-gen submerged actuators
These materials were fabricated into linear, ring-shaped spring structures and integrated into fully untethered underwater robotic prototypes. When exposed to ultraviolet or visible light, the actuators contract or expand, enabling controlled motion without needing batteries, wires, or pumps.
The artificial muscles exhibited actuation strains over three times greater than previous azobenzene-based systems and demonstrated a work capacity twice that of mammalian muscles.
The researchers also introduced a novel way to program motion by manipulating the chirality of the coiled springs—homochiral and heterochiral configurations allowed the direction of actuation to be reversibly designed. This flexibility enabled diverse robotic functions such as gripping, releasing, and crawling through confined underwater spaces.
According to the team, the soft robots maintained reliable performance across more than 100 light-actuation cycles, showcasing durability and precision. The ability to operate efficiently in submerged environments opens up new applications in underwater exploration, environmental monitoring, and soft robotics.
The team plans to commercialize the technology by 2030, focusing on improving material scalability and seamless system integration. They claim it marks a major step toward intelligent, untethered actuation systems for challenging environments.
The details of the team’s research were published in the journal Small.
Jijo Malayil Jijo is an automotive and business journalist based in India. Armed with a BA in History (Honors) from St. Stephen's College, Delhi University, and a PG diploma in Journalism from the Indian Institute of Mass Communication, Delhi, he has worked for news agencies, national newspapers, and automotive magazines. In his spare time, he likes to go off-roading, engage in political discourse, travel, and teach languages.
