The first half of the research was the development of a coating that can repel liquid and dust. This coating can be applied to paper or cardboard to prevent damage from moisture, but it also allows for layers of material to be printed.
This is where the second half of the research steps in; the printing of circuit layers directly to paper and cardboard. Using the specialized coating, researchers were able to print multiple circuit layers on-top of each other without them smudging or interfering with each other.
The resulting layers allowed for the construction of vertical Triboelectric Nanogenerators that both power circuitry and detect pressure on the paper. Since the other side of the paper is blank, a standard keypad interface can be printed, and thus a self-powered paper keypad can be created. The Triboelectric Nanogenerators are rapidly fabricated by using spray deposition of essential compounds including organosilanes, conductive nanoparticles, and polytetrafluoroethylene.
Read the original and detailed article here:
And watch the short video from Flexilab Purdue