A team from Rutgers University has developed a new 3D printing  method for a smart gel that could be used to create living structures in human organs and tissues, soft robots and targeted drug delivery methods.

The engineers new approach involves printing a 3D object with a hydrogel that changes shape over time when temperatures change.

The new smart gel could provide structural rigidity in organs, including the lungs, and can contain small molecules like water or drugs to be transported in the body and released. 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.

“The full potential of this smart hydrogel has not been unleashed until now,” Howon Lee, senior author of a new study and assistant professor in the Department of Mechanical and Aerospace Engineering at Rutgers University-New Brunswick, said in a statement. “We added another dimension to it, and this is the first time anybody has done it on this scale.

“They're flexible, shape-morphing materials. I like to call them smart materials,” he added.

The hydrogel has been used for several years in devices that generate motion as well as biomedical applications. However, hydrogel manufacturing has relied mainly on conventional, 2D methods including molding and lithography.

In the study, the researchers used a lithography-based technique that is fast, cheap and can print a wide range of materials into a 3D shape. The technique involves printing layers of a special resin to build a 3D object.

The resin consists of the hydrogel, a chemical that acts as a binder, another chemical that facilitates bonding when light hits it and a dye that controls light penetration.

The researchers found that in temperatures below 32 degrees Celsius, the hydrogel absorbs more water and swells in size. The objects that can be created with the hydrogel range from the width of a human hair to several millimeters long. The researchers can also grow one area of a 3D printed object—creating and programming motion—by changing temperatures.

“If you have full control of the shape, then you can program its function,” Lee said. “I think that's the power of 3D printing of shape-shifting material. You can apply this principle almost everywhere.”

The study was published in Scientific Reports.