A whiteboard of the future

May 1, 2015

The black side of the microparticles contains magnetic nanoparticles that make it possible to write on the screen. A magnet pulled across the surface of the white display attracts the black side and the balls flip to face the magnet. (credit: Yusuke Komazaki/University of Tokyo)

Researchers from the University of Tokyo have developed an inexpensive handwriting-enabled e-paper suited to large displays like whiteboards.

The display is made from black-and-white microparticles about 0.1 millimeter in diameter. One hemisphere of each particle is black and carries a negative charge, while the other is white and carries a positive charge. The particles are sandwiched between two electrodes. By switching the direction of the voltage across the electrodes the background display can be switched between black and white.

Handwriting with a magnet is demonstrated on a prototype of the new e-paper (credit: Yusuke Komazaki/University of Tokyo)

Such “twisting ball” displays are not new, but the researchers have integrated a magnetic field control component with the original electric control. The black side of the microparticles also contains magnetic nanoparticles that make it possible to write on the screen.

A magnet pulled across the surface of the white display attracts the black side and the balls flip to face the magnet. In this way images and lines can be drawn on the display. A magnet with about the strength of a refrigerator magnet will work for this task.

Applying a voltage will immediately erase the drawings. In the absence of a voltage or magnetic field, the image is maintained without using any energy.

“Toughness, cost, size and color are the advantages of our e-paper display,” said Yusuke Komazaki, a researcher in the Graduate School of Frontier Sciences at the University of Tokyo and lead author of a paper published in theĀ Journal of Applied Physics.

The display is made from materials like acrylic polymer, silicone elastomer, and silicone oil that are relatively inexpensive and hold up well under UV light. Because of the e-paper’s simple structure, large displays can be easily fabricated, Komazaki said. The researchers could easily change the color combinations by substituting different microparticle pigments, he suggested.

“Conventional electronic whiteboards are equipped with large LCDs or projectors and are very expensive, less visible in bright light conditions, heavy, and energy consuming,” Komazaki said. “If we fabricate super-large displays, it might even be possible to replace traditional blackboards in classrooms.”

The team is working to improve the contrast of the display, which they believe can be achieved by increasing the amount of black and white pigment in the microparticles. The researchers believe their work could one day contribute to a world less dependent on traditional paper.

Abstract of Electrically and Magnetically Dual-driven Janus Particles for Handwriting-enabled E-paper

In this work, we describe the synthesis of novel electrically and magnetically dual-driven Janus particles for a handwriting enabled twisting ball display via the microfluidic technique. One hemisphere of the Janus particles contains a charge control agent, which allows the display color to be controlled by applying a voltage and superparamagnetic nanoparticles, which allows handwriting by applying a magnetic field to the display. We fabricated a twisting ball display utilizing these Janus particles and tested the electric color control and handwriting using a magnet. As a result, the display was capable of permitting handwriting with a small magnet in addition to conventional color control using an applied voltage (80 V). Handwriting performance was improved by increasing the concentration of superparamagnetic nanoparticles and was determined to be possible even when 80 V was applied across the electrodes for 4 wt% superparamagnetic nanoparticles in one hemisphere. This improvement was impossible when the concentration was reduced to 2 wt% superparamagnetic nanoparticles. The technology presented in our work can be applied to low-cost, lightweight, highly visible and energy saving electronic message boards and large whiteboards because the large-size display can be fabricated easily due to its simple structure.