How many times have you stumbled in the dark, trying to locate a flashlight, only to discover the batteries inside it are dead? It’s an inconvenience in the middle of the night, but a genuine problem in an emergency, which is why this roll-up paper flashlight from Nendo seems like a brilliant idea for when the power unexpectedly goes out.

Made from YUPO, a durable, waterproof paper from a Japanese company called Takeo, the flashlight is covered in an electronic circuit board pattern that’s printed using conductive silver ink. It not only results in an eye-catching checkerboard design, it also adds additional functionality to the misleadingly simple flashlight.

The tighter the paper flashlight is rolled, the brighter it shines.

Attached to those printed circuits, using conductive glue, are two button-cell batteries and seven LEDs. To turn the flashlight on, you simply need to roll the sheet of paper into a tube which closes the circuit loop and sends power from the batteries to the LEDs. But the unique checkerboard circuit pattern means that the distance the electricity has to travel to the LEDs decreases as the paper tube is rolled tighter. Less distance means there’s also less electrical resistance encountered, so without the use of dials or buttons, the brightness of the paper flashlight can be adjusted by rolling it tighter or looser.

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Nendo hasn’t revealed exactly how bright the paper flashlight can get, but without a shiny reflector behind the LEDs to focus the beam, the intensity probably falls somewhere between the flash on the back of your smartphone, and a basic $10 LED torch. Don’t expect to illuminate a stadium, but you can certainly use this to find your way to the bathroom in the dark.

Roll it inside out and the flashlight’s glow goes from warm to cool.

You can also change the color temperature of the flashlight’s glow, from warm to cool, by simply rolling the tube inside out so that the LEDs shine through, and are tinted by, the paper. Unfortunately there doesn’t seem to be an easy way to get your hands on these paper emergency flashlights right now, at least outside of Japan, but the design and technology behind it doesn’t look particularly difficult to replicate. Whoever finds a way to cheaply mass produce these will make a fortune, as they seem like an obvious addition to any emergency preparedness kit.

[Nendo via designboom]