Some of the complex 3D shapes that can be formed from hydrogels using the new digital light printing method. Image: UT Arlington.
Some of the complex 3D shapes that can be formed from hydrogels using the new digital light printing method. Image: UT Arlington.

Living organisms expand and contract soft tissues to achieve complex, three-dimensional (3D) movements and functions, but replicating those movements with man-made materials has proven challenging. A researcher at the University of Texas at Arlington (UTA) has recently reported ground-breaking research in a paper in Nature Communications that could offer a solution to this challenge.

Kyungsuk Yum, an assistant professor in UTA's Materials Science and Engineering Department, and his doctoral student Amirali Nojoomi have developed a process by which two-dimensional (2D) hydrogels can be programmed to expand and shrink in a space- and time-controlled way that applies force to their surfaces. This causes the hydrogels to form complex 3D shapes and motions.

The novel process could potentially transform the way soft engineering systems or devices are designed and fabricated. Potential applications for the technology include bioinspired soft robotics, artificial muscles – which are soft materials that change their shapes or move in response to external signals as our muscles do – and programmable matter. The concept is also applicable to other programmable materials.

"We studied how biological organisms use continuously deformable soft tissues such as muscle to make shapes, change shape and move because we were interested in using this type of method to create dynamic 3D structures," Yum said.

His approach uses temperature-responsive hydrogels with local degrees and rates of swelling and shrinking. These properties allow Yum to spatially program how the hydrogels swell or shrink in response to temperature change using a specially developed digital light printing method that works in four dimensions, meaning the three physical dimensions plus time.

Using this method, Yum can print multiple 3D structures simultaneously in a one-step process. Then, he mathematically programs the structures' shrinking and swelling to form 3D shapes, such as saddle shapes, wrinkles and cones, and to control their direction.

He has also developed design rules based on the concept of modularity to create even more complex structures, including bioinspired structures with programmed sequential motions. This means shapes that are dynamic, able to move through space. He can also control the speed at which the structures change shape, and thus create complex, sequential motion, such as performed by stingrays as they swim in the ocean.

"Unlike traditional additive manufacturing, our digital light four-dimensional printing method allows us to print multiple, custom-designed 3D structures simultaneously," said Yum. "Most importantly, our method is very fast, taking less than 60 seconds to print, and thus highly scalable."

"Dr. Yum's approach to creating programmable 3D structures has the potential to open many new avenues in bioinspired robotics and tissue engineering. The speed with which his approach can be applied, as well as its scalability, makes it a unique tool for future research and applications," said Efstathios Meletis, professor and chair of Materials Science and Engineering at UTA.

This story is adapted from material from the University of Texas at Arlington, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.