Engineers from MIT and Singapore University of Technology and Design (SUTD) are using light to print three-dimensional structures that “remember” their original shapes. Even after being stretched, twisted, and bent at extreme angles, the structures, from small coils and multi material flowers, to an inch-tall replica of the Eiffel tower, sprang back to their original forms within seconds of being heated to a certain temperature sweet spot.
For some structures, the researchers were able to print micron-scale features as small as the diameter of a human hair, dimensions that are at least one-tenth as big as what others have been able to achieve with printable shape-memory materials. The team’s results were published earlier this month in the online journal Scientific Reports.
Nicholas X. Fang, associate professor of mechanical engineering at MIT, says shape-memory polymers that can predictably morph in response to temperature can be useful for a number of applications, from soft actuators that turn solar panels toward the sun, to tiny drug capsules that open upon early signs of infection.
“We ultimately want to use body temperature as a trigger,” said Fang. “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’s co-authors include former MIT-SUTD research fellow Qi “Kevin” Ge, now an assistant professor at SUTD; former MIT research associate Howon Lee, now an assistant professor at Rutgers University; and others from SUTD and Georgia Institute of Technology.
Ge said the process of 3D printing shape-memory materials can also be thought of as 4D printing, as the structures are designed to change over the fourth dimension, time.
“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,” said Ge. “This will advance 4D printing into a wide variety of practical applications, including biomedical devices, deployable aerospace structures, and shape-changing photovoltaic solar cells.”