Korea Chemical Technology Research Institute
Yong Seok Kim, Dong-Gyun Kim, Jae Hyuk Hwang and Jeong Jae Wie
The technology uses industrial sulfur waste to create flexible robots that move autonomously. The discovery could have implications for medicine and industry.
A team of researchers from South Korea developed a new 4D printing technology which transforms industrial sulfur waste into fully recyclable flexible robotscapable of moving autonomously in response to external stimuli such as heat, light and magnetic fields.
The was funded by the National Research Foundation of Korea and the US Army Research Laboratory and published in the journal Advanced Materials.
The innovation addresses a long-standing environmental challenge. Every year, oil refining generates million tons of elemental sulfurmuch of which is discarded or stored. The research team, led by Dong-Gyun Kim of the Korea Research Institute of Chemical Technology (KRICT), together with academics from Hanyang University and Sejong University, found a way to convert this waste into advanced robotic materials.
Unlike traditional 3D printing, which produces static objects, 4D printing creates structures that can change form or function over time when exposed to specific stimuli. The team achieved this by developing a new sulfur-rich polymer known as poly(phenylene polysulfide) networks (PSNs). These materials have shape memory properties, allowing printed structures to deform and return to their original form when stimulated by heat or light, without the need for motors or mechanical components.
To improve mobility, researchers incorporated magnetic particles in the material, making it possible to create small autonomous robots that can be guided by external magnetic fields. At less than 1.27 cm, these robots demonstrate precise and flexible movements, explains .
A fundamental innovation lies in the assembly process. Instead of stickers, the team uses a infrared laser close together to “weld” the components in seconds. This works by temporarily breaking and reforming the sulfur bonds, creating strong, seamless bonds between the pieces.
Researchers demonstrated the technology by building complex modular structures, including a miniature of the Sagrada Familia in Barcelona and a stadium with a retractable roof. Each structure was composed of multiple components with the ability to change shape, demonstrating the versatility of the system.
It is important to highlight that the material is fully recyclable. At the end of their life cycle, printed objects can be melted down and reused without any loss of quality, creating a closed-loop manufacturing process that minimizes waste.
Experts say the innovation could have major implications for flexible robotics, a field focused on flexible machines for use in areas such as medicine and precision manufacturing.
