June 27, 2019 | 84° F

Rutgers engineers print 4D gel with futuristic-like possibilities

Photo by Rutgers.edu |

Rutgers engineers have developed a process that prints 4D gel which molds its shape and size based on heat exposure. The Rutgers Today website features a video where chess pieces made of the hydrogel respond to changes in temperatures more than 32 degrees Celsius. 

Engineers at Rutgers University have discovered a way to 4D print a smart gel that could potentially prove invaluable to the future of science and medicine. 

Led by Howon Lee, an assistant professor at Rutgers’ School of Engineering, the manufactured material — or hydrogel — is highly reactive to heat and its shape and size is dependent on the surrounding temperature. The gel is initially 3D, but because it possesses the ability to change in shape and size, it is classified as 4D. 

The process in which a chess piece made of the hydrogel material responds to the change in temperature can be seen in a video on the Rutgers Today site.

As the temperature around the object increases beyond 32 degrees Celsius, the hydrogel shrinks, according to Rutgers Today. Conversely, as the temperature decreases, the chess piece grows in size. This reaction is due in part to the hydrogel material releasing and absorbing water vapor in response to temperature. 

“The highlight of this project is that we are able to quickly print temperature-sensitive hydrogel of 3D complex shape in micron scale,” said Zhaocheng Lu, a doctoral student at Rutgers in the School of Graduate Studies who is also working on the experiment. 

It has high fabrication speed, because the whole layer feature can be printed with one projection of a digital mask, Lu said. And because of the material’s water-absorbent and temperature-sensitive nature, its potential to function within the human body is very plausible. 

“Possible applications include soft robotic microdevices, targeted drug delivery and tissue scaffolds mimicking active bodily functions — all of which are exciting to us,” Lee said about potential uses in the future, according to Tech Briefs

It could also create a new area of “soft robotics” and enable new applications in flexible sensors and actuators, biomedical devices and platforms or scaffolds for cells to grow, Lee said.

Though an accomplishment, Lee said further development is still needed for it to become applicable in modern science. He explained that with full control of size and shape, people could create motion, program different functions or even make it work similarly to a robot.

“To better use this temperature-responsive shape-changing properties we should measure the mechanical properties of this printed hydrogel and dynamic theories can be applied on it,” Lu said. 

The idea for the 4D printing method arose from curiosity about what 3D printing would look like with an added dimension. 

Lee said he was working on micron-scale 3D printing with different kinds of photo-curable polymers. He decided he wanted to add another dimension, and chose a temperature-sensitive and photo-curable hydrogel.

“We were already working with 3D printing and wanted to find a way to add another dimension to it in order to give it different properties,” Lee said. “This project definitely has the potential to be used in the future for science, especially for administering drugs and medicine within the human body.” 

The material is commonly found within everyday products such as Jell-O, contact lenses and diapers, according to Tech Briefs. 

The machine uses a broad-spectrum light source to cure photopolymers by projecting 2D images using a Digital Micromirror Device known as microstereolithography, according to Dreams (Design, Research, and Education for Additive Manufacturing Systems). 

The process is a "lithography-based additive manufacturing technique that is fast, inexpensive and flexible in material selection," according to the team's report on the project.

“I got my master degree under Professor Lee’s advisement and both he and Professor Daehoon Han (a graduate student in the School of Engineering and co-author on the smart gel project) helped with my research," Lu said about his role. "This is the first project in our group, and I'm really proud of what we have accomplished.”

Christopher Robertson

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