New e-paper can be written on like a whiteboard

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A new e-paper display can be written and drawn on with a magnet (Image: Yusuke Komazaki/University of Tokyo)

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By repurposing and updating an e-paper technology from the 1970s, researchers from the University of Tokyo have created a cheap but tough new electronic display that can be written on with a magnet. This new e-paper could be used in low-cost, lightweight electronic whiteboards as well as traditional classroom blackboards, and its creators hope that it will eventually reduce our dependence on real paper.

The e-paper came about by modernizing a technology created in the 1970s called "twisting ball displays." The twisting ball part of the name comes from how bicolored microparticles move around on an elastic silicone sheet when sandwiched between two parallel electrodes. The particles change color and exhibit different charge properties in each hemisphere, and this causes them to rotate in the same direction as the electric field. If you change the direction of the voltage, the display changes color.

For their new system, the Japanese researchers added the ability to control the flow of particles with a magnetic field. The black side of the microparticles carries not only a negative charge, but also a number of magnetic nanoparticles that are attracted to magnets pulled across the surface of the white display. In this way the microparticles flip around to face the magnet, making it possible to draw images and lines on the display with a magnetized pen. To clear the display you need only apply a voltage.

The researchers note that their e-paper display is cheap, tough, and highly scalable, and its color combinations could be easily changed for improved aesthetics or readability by substituting different microparticle pigments.

They also suggest that this new e-paper could have a competitive advantage. "Conventional electronic whiteboards are equipped with large LCDs or projectors and are very expensive, less visible in bright light conditions [compared to the e-paper], heavy, and energy consuming," says lead author Yusuke Komazaki. "If we fabricate super-large displays, it might even be possible to replace traditional blackboards in classrooms."

Their next step will be to test higher amounts of black and white pigment in the microparticles to see if that improves the display contrast. From there they hope to see the technology move the world closer to abandoning real paper – which is less re-usable and contributes to deforestation – in favor of handwriting-enabled e-paper.

A paper describing the research was published in the Journal of Applied Physics.

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