A domestic research team has developed a circular 4-dimensional (4D) printing technology that uses sulfur discarded from oil refineries to move on its own and even be recycled.
Kim Dong-gyun, principal researcher at the Korea Research Institute of Chemical Technology (KRICT) Chemical Materials Research Division, along with Hanyang University professor Wi Jeong-jae and Sejong University professor Kim Yong-seok, said on the 4th that their joint team has developed, for the first time in the world, 4D printing technology that responds to temperature, light, and magnetic fields using sulfur polymers.
In recent years, studies have reported recycling sulfur byproducts discarded from oil refining into sulfur plastics. Sulfur plastics transmit infrared light that ordinary plastics cannot, making them usable as materials for infrared camera lenses, and they can also be used for water purification by adsorbing heavy metals.
However, the interior of sulfur plastics is entangled like a net and has low fluidity, creating limitations in applying three-dimensional (3D) printing technology.
The researchers designed the internal net-like structure of sulfur plastics to be looser so they could be printed. In particular, they developed 4D printing technology that enables "shape memory," in which the shape changes in response to stimuli such as temperature or light, by precisely controlling the sulfur content and the net structure of the sulfur plastic.
When a special laser was shone for 8 seconds on the material made with the developed technology, pieces could be bonded firmly without adhesive. The team also developed a soft robot smaller than 1 centimeter that moves without an external power source by mixing 20% iron powder into the sulfur plastic.
Kim said, "This study is the first case of upcycling sulfur, an industrial byproduct, into an advanced robotic material," adding, "Smart materials that can move on their own and be recycled will become a key driver of future soft robotics and automation industries."
The findings were published in the international journal "Advanced Materials" in Nov. last year.
References
Advanced Materials (2025), DOI: https://doi.org/10.1002/adma.202507057