With a 3D printer, an operator plugs in a virtual blueprint for an object, which the printer uses to construct the final product layer by layer. To make something "4D," though, Tibbits feeds the printer a precise geometric code based on the object's own angles and dimensions but also measurements that dictate how it should change shape when confronted with outside forces such as water, movement or a change in temperature.

In short, the code sets the direction, the number of times and the angles at which a material can bend and curl. When that object is confronted with a change in environment, it can be stimulated to change shape. Pipes, for instance, could programmed to expand or shrink to help move water; bricks could shift to accommodate more or less stress on a given wall.
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Tibbits demonstrated the concept of 4D printing at a TED talk last year, during which he showed how a single strand of printed material could be programmed to fold, on its own, into the word “MIT.” The shapes of things to come At face value, it's a concept that's very cool. But when can we expect to see these kinds of transformations out in the real world? In some cases, they're already happening. Tibbits points out that in nanotechnology, scientists have been able to program physical and biological materials to change their shapes and properties—such as using DNA to self-assemble nanorobots.

Making this happen on a human scale, he concedes, is much more challenging, particularly in more traditional industries, such as construction. But Tibbits says at least one company is interested is seeing how 4D programming can be applied to infrastructure. There's potential, he says, in using self-assembling materials in disaster areas or extreme environments where conventional construction is not feasible or too expensive. For instance, he sees a future for what he calls “adaptive infrastructure” in space.

Tibbits say his lab is working closely with a number of industry partners on ways they could incorporate the 4D concept into their businesses. As for where we might see transforming products on the shelves, Tibbits envisions innovation in furniture or sportswear. He offers the example of sneakers that could change shape and function in response to how they're being used.

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Here’s some other recent developments in 3D and 4D printing: Army maneuvers: The U.S. Army has given a grant to Harvard University, University of Pittsburgh and University of Illinois to explore ways the military could use self-assembling objects, raising the possibility of shelters or bridges that spring into shape. Just don't tell anyone your makeup came right off the printer: Harvard student Grace Choi has created a prototype for a 3D printer called "Mink" that is designed to let users choose any color imaginable and then actually print out makeup in that hue. All in a day's work: In China, an engineering company used 3D printers to build 10 one-story houses in a day. The printers, which were 33 feet wide and 22 feet high, used a mix of cement and construction waste to build the walls layer by layer.  
Source : http://www.smithsonianmag.com/innovation/Objects-That-Change-Shape-On-Their/"