At the 2013 IEEE International Conference on Robotics and Automation (ICRA) in Germany a 3D printed inchworm robot was demonstrated that can self-assemble. The little robot was is made from shape memory polymers that contract when heat is applied to flexible connectors that are etched into the material.
The inchworm was developed by Samuel Felton and colleagues at the School of Engineering and Applied Sciences and the Wyss Institute for Biologically Inspired Engineering at Harvard University and the Computer Science and Artificial Intelligence Laboratory at MIT. It was made to demonstrate sequential folding, angle-controlled folds, slot-and-tab assembly, and mountain and valley folds.
The creators hope that their project will pave the way for robots to be created with cheap materials using an assembly process that requires no human intervention. The trickiest part of the assembly is the folding of the robot itself, with the installing of the battery and motor being trivial enough for a human. Although this could be automated easily using a robotic pick and place machine, which would allow production to be massively scaled up.
For a more in-depth explanation of the technology go to IEEE Spectrum, watch this video to see the inchworm robot do its folding action.