4D printing is more real than you can think

3D printing is the current hype in the tech world. People are amazed with the ability to print their imagination in 3D and do all kind of stuff with it. Its a boon for artists and innovators. While the world is looking to expand the horizon of 3D printing, there is a group of people who are thinking about 4D printing.
4D printings adds the dimension of time to materials i.e. programmable materials which can self assemble or disassemble in real time depending on the type of stimuli. The idea of 4D printing comes from shape memory alloys which used thermoelastic displacive transformation like thermoelastic martensitic transformation to change shape with stimuli.
But advances in 4D printing is going to herald a new era of materials that can build themselves. The MIT's Self Assembly lab is working on the technology of 4D printing. They are currently printing interwoven materials with different thermal properties thus on exposing to temperature change they tend to behave similar to shape memory alloys.

New shape-shifting Alloy discovered

Crystals seen on the fine scale: River-like patterns form and change as the metal morphs

Scientists have found a new alloy that can change its shape inumerous times without any fatigue or strain development. This new material called a "martensite" has two different arrangements of crystal structure and the alloy can seamlessly shift between the two. This shift is caused by variation of temperature and as the shifts between one structure to another with temperature and return to original structure if temperature is returned to its initial value, it is also know an shape memory alloys.
The current shape shifting materials are made of Nickel and Titanium. These have been employed in various fields including the solar panels of Hubble telescope, but the problem with these are that  after repeated cycle of temperature variations it starts creating strain internally and degrades. This leads to its eventual failure, but the new alloy composed of zinc, copper and gold can go thousands of cycles with virtually no stress and can go on for a very long time.
Thus, this has open new scopes for these active materials.

Read More at :-http://www.bbc.co.uk/news/science-environment-24400101
Read the Article in Journal Nature:- http://www.nature.com/nature/journal/v502/n7469/full/nature12532.html