A few months ago, MIT managed to create 3D printed objects that could be adapted even after they were printed. Like any responsive material, however, the polymers they used could only be altered using an outside source, in this case light. Now, MIT researchers have created something new: a 3D printed structure that begins to fold itself as soon as it is peeled off the printing platform.

The material the researchers use is new printer-ink that expands as it solidifies, rather than contracting as most other printer-ink materials do. As printed objetcs are built up in layers, the MIT researchers deposit their expanding material at precise locations on either the top or the bottom few layers. The bottom layer adheres slightly to the printer platform, which is enough to hold the structure flat. As soon as the device is peeled from the surface, the new material starts to expand, bending the joints in the opposite direction.

The researchers built several prototypes of the same design, showing that they can control the precise angle at which the joints fold. Even after forcibly straightening the hinges, the joints fold back to the original folds as soon as they are released.

The researchers printed a prototype self-folding printable device that includes electrical leads and a polymer ‘pixel’ that changes from transparent to opaque when a voltage is allied to it. The 3D printed structure starts out looking like the letter H, but once it is peeled from the printing platform, the ‘legs’ start to fold. The result is a sort of table top shape.

The advantage of self-folding structures without any outside stimuli is that they can involve a wider range of materials and more delicate structures, according to the researchers. Examples include printed electronics in organic materials, which are very sensitive to moisture and temperature. This provides an opportunity to create functional electronics in 3D printed objects.

Images: MIT