4-D printing takes “smart” materials from a 3-D printer that can assemble themselves. So instead of just printing out a chunk of shaped plastic, you can actually create shapes that a fixed 3-D printing nozzle couldn’t accomplish. The potential uses for this range from extreme condition architecture to adaptive infrastructure, like pipes that expand and contract depending on water volume. There’s also potential in medicine: various implants could be inserted in a packed form, then take their true shape once they reach their destination.
Read more: http://www.businessinsider.com/what-is-4-d-printing-2014-5