When you print 3D objects on your 3D printers, they remain stable. Other than deteriorating over time, the objects do not change by themselves. However, that may be changing now. Scientists at MIT have created a new technique of printing 3-D objects where you can change the polymers in the object after printing. That means change the color of the object, grow or shrink it, or even change its shape entirely.

Associate Professor of Chemistry at MIT, Jeremiah Johnson led the research, along with Postdoc Mao Chen, and graduate student Yuwei Gu. They have written a paper on the findings, and they call the technique living polymerization. According to the team, the process creates materials whose growth can be stopped and started at will.

As they explain, after printing the material, it is possible to morph it into something else using light, even growing the material further. For instance, the team used a 3-D printed object immersed inside a solution. When they shined Ultra Violet light on the object, while it was still immersed, the resulting chemical reaction released free radicals. The free radicals bound themselves to other monomers within the solution and added them to the original object. According to the team, the process was highly reactive, and damaged the object.

At another study at the Wyss Institute for Biologically inspired Engineering of Harvard University, Dr. Jennifer Lewis is a senior author on a study on shape-shifting objects created using a 3-D printer. The team has devised a technique that allows printed objects to change their shape according to the environment.

According to the researchers at Wyss Institute, the printer creates a structure that can shift its shape. For instance, when immersed in water, the structure folds into complex and beautiful designs. The researchers claim they can adapt the process so that the printed object can fold into prescribed shapes when cooled, heated, or injected with an electrical current.

The researchers are of the opinion the technology could pave the way for generating new types of medical implants. Folding into shape when inserted into the body, such implants could generate a new family of soft electronics. According to Dr. Lewis, this is an elegant advance in the assembly of programmable materials, which a multidisciplinary approach made it possible to achieve. This has taken them farther than merely integrating form and function for creating transformable architectures.

The researchers have published their work in the journal Nature Materials. They say they were inspired by the manner in which plants grow and change their shape over time, as plants and flowers contain microscopic structures as tissues allowing them to change their shape as their environment changes. For instance, depending on temperature and humidity, plant leaves, flowers, and tendrils open or fold up.

Dr. Lewis used a printable hydrogel as it swells when added to water. The team designed specific structures under control that would change shape when placed in water. They derived the hydrogel ink from wood, and the ink had cellulose fibrils very much like the structures in plants that allow them to change shape.