November 9, 2013 - The advent of 3-D printing brought on a number of innovations worthy of news coverage. Printers have created prosthetic hands, action figures, food, even blood vessels, simply by depositing layer after layer of different kinds of ink.
Now a handful of engineers around the world are trying to push the boundaries one step further — by printing objects that can build themselves.
It's called 4-D printing, and the fourth dimension in this case is time. Here's how it works: A 3-D printer with extremely high resolution uses materials that can respond to outside stimuli, like heat or light, as ink. The resulting structure can change, move or even assemble itself after it's been printed.
One team of researchers led by H. Jerry Qi, an associate professor at the University of Colorado Boulder, is using heat and mechanical pressure to transform flat objects into three-dimensional structures. They printed an unfolded box with glassy polymer fibers — a composite material that has "shape memory behavior" — along the folds. They heated it, pulled on the sides and cooled it, and the flat structure responded by folding into a box.
Another team — a collaboration between University of Pittsburgh, University of Illinois at Urbana-Champaign and Harvard University — recently garnered an $855,000 grant from the U.S. Army Research Office to explore how adaptive materials can respond to stimuli like light or temperature.
It's not unlike how the body works, says Professor Anna Balazs at Pittsburgh.