If you forgot what is 4d printing here is a new overview. Hint: fourth dimension is the time.
Good people from MIT made this robotic forms that move in preassigned forms when exposed to heat. They are also working on self-folding laser-cut materials and present designs for resistors, inductors, and capacitors, as well as sensors and actuators - the electromechanical “muscles” that enable robots’ movements.
Harvard has also their technology in the game "Self-assembling Sensors for Printable Machines," by ByungHyun Shin, Samuel M. Felton, Michael T. Tolley, and Robert J. Wood from the Wyss Institute for Biologically Inspired Engineering at Harvard University, presented at ICRA 2014:
Harvard engineers created a self-assembling lamp whose components are printed, including some of the electronics.
The thing that comes out of the printer (it's a rather special sort of printer) is a flat multi-layer sandwich of shape-memory polymers (they take care of the actual folding, triggered by heat), thin layers of copper, layers of paper and foam for structure, and double-sided tape to keep it all stuck together.
Obviously, not every single part of this lamp was printed. Discrete components like the LED were manually soldered to the composite before folding, and the lamp was wired into an Arduino to get the capacitive touch sensor to properly control the LED.Source: http://spectrum.ieee.org/automaton/robotics/diy/harvard-self-folding-printable-lamp
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