Study Pioneers Advanced ‘4D Printing’ Process

A newly released study showcases polymers that can be shaped using a 3D printer, "remember" that structure and quickly revert to it on command.

Researchers from the Massachusetts Institute of Technology and the Singapore University of Technology and Design said that 4D printing, or printed structures that change over time — the fourth dimension — could be useful for robotics, energy, health care and a variety of other industries.

So-called shape-memory polymers — which shift between a harder, yet amorphous, state at lower temperatures and a rubbery state at hotter conditions — aren't new, but they are limited by the size constraints of conventional 3D printers.

MIT and SUTD scientists, however, pioneered a new process that allowed them to print layers about 10 times smaller than possible with previous 3D printing.

The system, called microstereolithography, uses light from a projector to print patterns on successive layers of resin.

“It’s almost like how dentists form replicas of teeth and fill cavities, except that we’re doing it with high-resolution lenses that come from the semiconductor industry," said MIT engineer Nicholas X. Fang. "Which give us intricate parts with dimensions comparable to the diameter of a human hair.”

Those smaller sizes also allow for faster reaction times when the polymers are exposed to heat. Even after researchers bent the small structures at extreme angles, they reverted to their original shapes within seconds, according to the study published in the journal Scientific Reports.

Fang added that if the dimensions are eventually reduced further, "we may also be able to push their response time to milliseconds.”

Scientists said that the printing process and polymer structures could be applied to solar panel actuators, deployable aerospace structures or drug capsules capable of targeting infections at the earliest signs of symptoms.

“We ultimately want to use body temperature as a trigger,” Fang said.