The team started with a flat sheet, to which it added two motors, two batteries, and a microcontroller, which acts like the robotâ€™s brain, Felton said. The sheet was a composite of paper and Shrinky Dinks, also called polystyrene, and a flexible circuit board in the middle. It also included hinges that were programmed to fold at specific angles. Each hinge contained embedded circuits that produce heat on command from the microcontroller. The heat triggers the composite to fold itself in a series of steps.