Paper-based electronics are fine and dandy, but where do you stick the buttons? That’s a problem that has confronted engineers ever since they first created ultrathin batteries and solar cells by grafting nanometer-thick layers of metals, carbon nanotubes, or photovoltaic cells onto paper. Now a team led by a mechanical engineer has developed a paper-based keypad  that allows people to interact with this floppy future. The researchers started with paper coated with a thin layer of aluminum normally used in book covers. They then etched 10 buttons (above) into the metal with a laser cutter. This created breaks in the conductive area across the material. Finally, they attached the device to a cardboard box outfitted with an alarm. Touching the lines in each button bridged the breaks in the metal, changing the electrical charge. And those changes turned off the alarm, the researchers will report in an upcoming issue of Advanced Materials. The keypad cost the scientists $50 to make, but they believe they can cut the price. If so, the advance could lead to a new generation of cheap, disposable devices, like one-use chips to diagnose malaria and HIV, for the developing world.
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