Korean Team Unveils World’s First 4D Printing with Sulfur Waste

A research team from South Korea has made significant strides in 4D printing technology by developing a method that utilizes waste sulfur produced during petroleum refining. This pioneering work, led by Dr. Dong-Gyun Kim at the Korea Research Institute of Chemical Technology (KRICT), alongside researchers from Hanyang University and Sejong University, introduces self-actuating and recyclable structures made from sulfur-rich polymers.

The team’s innovation addresses the pressing need to convert industrial by-products into valuable resources. According to the United States Geological Survey (USGS), global sulfur production reached approximately 85 million tons in 2024, primarily as a by-product of petroleum refining. The development of what the researchers call “sulfur plastics” aims to transform this abundant material into a high-value resource. These plastics not only possess unique properties—such as the ability to transmit infrared light and capture heavy metals—but also represent a sustainable solution to waste management.

Overcoming Challenges in 3D Printing

Despite the advantages of sulfur plastics, their application in 3D printing has been limited due to their densely cross-linked structures, which impede flowability. The research team overcame this challenge by engineering a loosely cross-linked sulfur polymer network. This modification allows for easier extrusion and printing into complex 3D shapes. By precisely tuning the sulfur content and polymer structure, the team achieved 4D printing capabilities, where structures can autonomously change shape in response to heat or light.

A notable aspect of this technology involves the use of a near-infrared (NIR) laser. When applied for just eight seconds, the laser initiates a chemical welding process, temporarily breaking and reconnecting internal bonds. This unique feature enables printed components to join seamlessly without adhesives, facilitating the creation of intricate 4D structures akin to assembling LEGO blocks.

Innovative Applications and Future Impact

The research team also incorporated magnetic particles into their designs, resulting in soft robots measuring less than 1 cm that can move autonomously without the need for external power sources. By combining the shape-memory properties of the polymer with magnetic responsiveness, these robots can perform guided movements based on external magnetic fields.

Another crucial feature of this technology is its closed-loop manufacturing capability. Once their utility has been exhausted, the printed structures can be melted down and reused as feedstock for further printing, achieving a complete recycling process. This innovation establishes a resource-circulating manufacturing system, which is vital for sustainable development.

Dr. Dong-Gyun Kim emphasized the significance of this research, stating, “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 groundbreaking research were published in the scientific journal Advanced Materials. The project received support from the KRICT core research program, the Ministry of Science and ICT of Korea, and the U.S. Army International Technology Center.

KRICT, established in 1976, is a non-profit research institute funded by the Korean government. It plays a pivotal role in advancing national chemical technologies across various fields, including chemistry, materials science, and environmental science. The institute aims to tackle pressing challenges in chemistry and engineering, contributing to a sustainable future.

For more information about KRICT and its initiatives, visit their official website at https://www.krict.re.kr/eng/.