Soon, 3D printed robots that self-assemble when heated

Soon, you may 3D-print a robot at home and then watch it assemble itself!
MIT scientists have developed new algorithms and electronic components that could enable printable robots that self-assemble when heated.
A group led by Daniela Rus, from the Massachusetts Institute of Technology (MIT) and its collaborators have introduced the idea of bakable robots.
In two new research papers, the researchers demonstrate the promise of printable robotic components that, when heated, automatically fold into prescribed three-dimensional configurations.
One paper describes a system that takes a digital specification of a 3D shape - such as a computer-aided design, or CAD, file - and generates the 2D patterns that would enable a piece of plastic to reproduce it through self-folding.

The other paper explains how to build electrical components from self-folding laser-cut materials. The researchers present designs for resistors, inductors, and capacitors, as well as sensors and actuators - the electromechanical "muscles" that enable robots' movements.

"We have this big dream of the hardware compiler, where you can specify, 'I want a robot that will play with my cat,' or 'I want a robot that will clean the floor,' and from this high-level specification, you actually generate a working device," Rus said.
"So far, we have tackled some subproblems in the space, and one of the subproblems is this end-to-end system where you have a picture, and at the other end, you have an object that realises that picture. And the same mathematical models and principles that we use in this pipeline we also use to create these folded electronics," said Rus.

Both papers build on previous research that Rus did in collaboration with Erik Demaine, also from MIT. This work explored how origami could be adapted to create reconfigurable robots.
The key difference in the new work, said Shuhei Miyashita, a postdoc in Rus' lab, is a technique for precisely controlling the angles at which a heated sheet folds.
Miyashita sandwiches a sheet of polyvinyl chloride (PVC) between two films of a rigid polyester riddled with slits of different widths. When heated, the PVC contracts, and the slits close. Where edges of the polyester film press up against each other, they deform the PVC.

Imagine, for instance, a slit in the top polyester film and another parallel to it in the bottom film. But suppose, too, that the slit in the top film is narrower than that on the bottom.
As the PVC contracts, the edges of the top slit will press against each other, but there will still be a gap between the edges of the bottom slit.
The entire sheet will then bend downward until the bottom edges meet as well. The final angle is a function of the difference in the widths of the top and bottom slits.