E-reader out of juice? Just give it a rub. That's the idea behind Paper Generators, developed by Disney Research in Pittsburgh, Pennsylvania, which use nothing more than cheap foil and a sheet of Teflon to generate power from users' rubbing or tapping.
The Teflon is given a negative charge by rubbing it with paper before it is sandwiched between two thin sheets of metal foil. Because Teflon is a type of material known as an electret – one which produces its own electrostatic charge – it holds this small charge for many years.
When the user rubs or taps the foil, current flows from the negatively charged Teflon through the positively charged foil, creating a circuit. The foil is wired to whatever electronics the device is powering. The prototype can produce 44 milliwatts of power, enough to run an array of LEDs or e-ink display. The device also works if a single sheet of foil is rubbed with a sheet of Teflon.
Charging cheaply
Project leader Ivan Poupyrev says Paper Generators are promising because the materials are inexpensive: "The cheapness of this technology is amazing. We can print it on the walls, tables and chairs. It's scalable to massive sizes like no other technology. You could think about an entire building covered with this, generating power from the wind blowing past it."
Paper Generators are never going to produce large amounts of power, but Poupyrev envisions future versions of the device being used in novel super-low-power devices – reloadable e-ink magazines that don't need charging or batteries, or smartwatches that never run flat.
"To turn the magazine on, you would just rub the pages together," says Poupyrev. An e-ink watch could be rubbed to show the time when out of power.
Team member Mustafa Emre Karagozler is due to present the prototype at the User Interface Software and Technology conference in St Andrew's, Scotland, this week.
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