Apparently, they are trying to create objects that, when given an outside stimulus, will change into something else. So, you could print a coffee cup, and when hot coffee is poured into it, the cup would expand to prevent your hand from burning.
http://www.cnn.com/2013/04/10/tech/innovation/orig-ideas-4-d-printing/index.html
That is pretty damn cool. Thanks.
I didn't understand why this printer is called 4D? it is just 3D...Am I wrong?
The objects that are printed are 3D, but because the objects change shape according to outside stimuli you are presumably adding another dimension making it 4D. That's my guess anyway. A bit like space-time being the fourth dimension in the universe. That or 4D printing is just a cool name made up by some marketing bod. If so, it worked on me!