Korean Researchers Unveil First 4D Printing Tech Using Sulfur Waste

A research team from South Korea has made a significant breakthrough in 4D printing technology by developing a method that utilizes waste sulfur from petroleum refining processes. The project, led by Dr. Dong-Gyun Kim at the Korea Research Institute of Chemical Technology (KRICT), along with collaborators from Hanyang University and Sejong University, has produced self-actuating, recyclable structures using sulfur-rich polymers.

This innovative technology addresses the substantial amounts of elemental sulfur generated in petroleum refining. According to the United States Geological Survey (USGS), global sulfur production reached approximately 85 million tons in 2024. Transforming this industrial by-product into valuable resources is increasingly important, highlighting the potential of “sulfur plastics” as circular materials that can contribute to both environmental sustainability and advanced manufacturing.

Sulfur plastics possess unique properties, including the ability to transmit infrared light, making them suitable for applications such as infrared camera lenses. Additionally, they can capture heavy metals, which opens up possibilities for water purification systems. Despite their advantages, integrating sulfur plastics into traditional 3D printing has been challenging due to their densely cross-linked structures, which hinder flowability.

To overcome these limitations, the research team engineered a loosely cross-linked sulfur polymer network. This modification allows the material to be easily extruded and printed into complex 3D shapes. By carefully controlling the sulfur content and network structure, the researchers achieved 4D printing with shape-memory properties. These structures can autonomously change their shapes in response to heat or light, eliminating the need for additional mechanical systems.

Applying a near-infrared (NIR) laser for just eight seconds initiates a chemical welding process within the printed components. This process temporarily breaks and reconnects internal bonds, enabling parts to fuse together without adhesives. This capability allows for the assembly of complex 4D structures, akin to building with LEGO blocks.

Furthermore, the team incorporated 20% magnetic particles into the polymer, leading to the development of soft robots measuring less than 1 cm. These robots can move autonomously, driven by external magnetic fields, showcasing the potential for sophisticated applications in soft robotics.

An essential aspect of this technology is its closed-loop manufacturing capability. After their initial use, the printed 4D structures can be melted down and reused as feedstock, achieving complete recycling of materials. This creates a sustainable resource-circulating manufacturing system.

Dr. Kim remarked, “This study represents the first example of upcycling industrial sulfur waste into advanced robotic materials. Smart materials that can move autonomously and be recycled are expected to become key drivers of future soft robotics and automation technologies.”

The findings of this research were published in the journal Advanced Materials. KRICT has been at the forefront of chemical technology development since its establishment in 1976, focusing on enhancing national capabilities in chemistry, material science, and engineering. The institute aims to position itself as a global leader in addressing critical challenges in these fields, contributing to both technological advancement and environmental stewardship.

Support for this research was provided by the KRICT core research program, the Ministry of Science and ICT of Korea, and the U.S. Army International Technology Center. For more information about KRICT and its initiatives, visit their official website at https://www.krict.re.kr/eng/.