Inspired by the movements of stingrays, engineering researchers have created programmable hydrogels that can expand and contract into 3D shapes and potentially move through space.
While living organisms can complete complex, 3D movements, replicating those features in man-made materials is a big challenge.
“We studied how biological organisms use continuously deformable soft tissues such as muscle to make shapes change and move because we were interested in using this type of method to create dynamic 3D structures,” said research team lead Assistant Professor Kyungsuk Yum, from the Materials Science and Engineering department at the University of Texas, Arlington (UTA).
According to UTA’s Engineering Department Chair Stathis Meletis, Yum’s approach to creating programmable 3D structures could 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,” Meletis said.
Temperature control
Yum and his PhD student, Amirali Nojoomi, developed a method using digital light 4D printing (DL4P) to produce hydrogels with a pre-programmed response to temperature. Their findings were recently published in Nature Communications.
The hydrogels are programmed during the printing process by using a greyscale pattern to expose the material to a controlled intensity of light. This introduces crosslinks in the hydrogels which causes them to swell or shrink at a pre-programmed transition temperature.
The rate, extent and direction of expansion and contraction can be programmed, which allows the materials to form complex 3D shapes and structures. Yum also devised design rules for programmed sequences of motion to mimic a stingray swimming.
This method of engineering materials capable of reversible shape changes could be used in a wide range of applications, from soft robots to medical devices such as endovascular stents, and has also been used to produce origami-like self-folding structures.
Another possible application is artificial muscles, which could flex in response to external signals such as electrical currents.
According to Yum, the DL4P has other advantages over traditional manufacturing methods for reversible shape changing materials, including the ability to print several structures at the same time.
“Most importantly, our method is very fast, taking less than 60 seconds to print, and thus highly scalable,” he added.