Scientists from Carnegie Mellon University have done something interesting to plain ol' paper. They've coated it with patterns of a conductive thermoplastic, which causes the paper to bend, fold or flatten in response to an electrical current.
The process starts with a half-millimeter-thick continuous filament of a melted thermoplastic – commercially-available graphene polylactide composite – being deposited on regular copy paper using an inexpensive FDM (Fused Deposition Modelling) 3D printer. Known as a Printed Paper Actuator, the resulting paper/plastic device is next heated in an oven or using a heat gun, then bent or folded into the desired shape, and finally left to cool.
Electrical leads are subsequently attached to it. As long as no current is delivered into the electrically-conductive thermoplastic, the actuator retains its default bent/folded shape. When a current is applied, however, the plastic heats up and expands, causing itself and the underlying paper to flatten out. As soon as the current is shut off, the device folds up again.
Led by assistant professor Lining Yao, the researchers have additionally used the conductive thermoplastic to add touch-sensitive controls to the actuators. They're now experimenting with altering the 3D-printing speed and/or width of the filaments to achieve different folding effects, and are looking at increasing the actuation speed via paper that's more heat-conductive, or plastic that's optimized for use in the actuators.
"We are reinventing this really old material," says Yao. "Actuation truly turns paper into another medium, one that has both artistic and practical uses."
You can see some potential applications of the technology, in the video below.
Source: Carnegie Mellon University
