3D printers make objects by piling layers of material on top of each other according to a preset design.

While the printing technology is impressive, it generally makes objects that are fixed in position after they are made. Now scientists say they have come up with so-called 4D printing technology which makes objects that can change shape over time. The full research paper was published in the journal Scientific Reports.

4D Printing
Photo by keepitsurreal

Study creates “shape-memory polymers”

The developments could be applied to many different scientific fields following research by scientists at MIT and the Singapore University of Technology and Design (SUTD). Their research shows how 3D printed objects can change shape when exposed to stimuli like heat, light or electricity.

These changes are possible thanks to special properties of “shape-memory polymers,” which are capable of “remembering” how they were originally even after changing shape.

In the MIt/SUTD study, scientists made a 3D-printed replica of the Eiffel Tower, which they then bent out of shape and “froze” at room temperature. They later applied heat to the replica and watched as it turned back into the shape of the Eiffel Tower.

4D printing structures remember original shape

The printing technique used in the study is called microstereolithography. It uses projected light to print a design on layer after layer of resin. An article in MIT News reveals that the technique can be used to print objects that are just as wide as a human hair, which is ten times smaller than objects made by rival shape-memory printing efforts.

“Because we’re using our own printers that offer much smaller pixel size, we’re seeing much faster response, on the order of seconds,” Nicholas X. Fang, one of the MIT researchers, told MIT news. “If we can push to even smaller dimensions, we may also be able to push their response time, to milliseconds.”

The team found that the tiny objects could be stretched and buckled out of shape without breaking. Exposure to higher temperatures would make the objects regain their original shape within seconds.

Multiple fields could benefit from technology

The use of small objects means that they return to their original shape faster than the objects used in previous studies. However the team believes that further improvements can be made.

“The reality is that, if you’re able to make it to much smaller dimensions, these materials can actually respond very quickly, within seconds,” Dr. Fang told MIT News. “For example, a flower can release pollen in milliseconds. It can only do that because its actuation mechanisms are at the micron scale.”

It is thought that the 4D printing technology could be used to make hinges for solar cells so that they can follow the sun, as well as self-deploying structures that could be used in aerospace.

“Our method not only enables 4D printing at the micron-scale, but also suggests recipes to print shape-memory polymers that can be stretched 10 times larger than those printed by commercial 3D printers. This will advance 4D printing into a wide variety of practical applications, including biomedical devices, deployable aerospace structures, and shape-changing photovoltaic solar cells,” Ge said.

The use of the 4D printing technology in medicine is particularly interesting. “We ultimately want to use body temperature as a trigger. If we can design these polymers properly, we may be able to form a drug delivery device that will only release medicine at the sign of a fever,” Fang said in a statement.