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Electronic Inks Allow More Efficient Displays
An electric field organizes dumbbell-shaped nanoparticles into amazing colors.
Credit: Eric Dufresne, Yale University; Eric Furst, University of Delaware

This Research in Action article was provided to LiveScience in partnership with the National Science Foundation.

No, this isn't an impressionist painting of tiger lilies at the height of their summer brilliance. These colors are produced when dumbbell-shaped polymer nanoparticles in suspension come in contact with an electric field. Forces created by the voltage drive the nanoparticles to form a tightly organized crystalline structure. This structural transformation gives off a vivid orange color. When the voltage is removed, the crystal dissolves and the color reverts to white.

A close-up view of a microscopic electron micrograph of the organized dumbbell nanoparticles.
A close-up view of a microscopic electron micrograph of the organized dumbbell nanoparticles.
Credit: Eric Dufresne, Yale University; Eric Furst, University of Delaware

From shimmery butterflies to iridescent seashells, Mother Nature creates color when structural components capture and reflect light. While the naturally occurring palates are always "on" the color generated by aligned nanoparticles toggles on and off. Controlling nanoparticle output would allow researchers to create more energy-efficient color display technologies for both industrial and consumer applications, including cell phone, laptop and tablet displays.

Such an advance would resolve challenges presented by current display technology. Conventional liquid-crystal displays require a great deal of energy because they emit their own light. Suspension-based electrophoretic inks — popular in electronic book readers — reflect light from their surroundings, making them more energy efficient. However, existing ink technologies limit display color to black and white.

A microscopic electron micrograph of the organized dumbbell nanoparticles.
A microscopic electron micrograph of the organized dumbbell nanoparticles.
Credit: Eric Dufresne, Yale University; Eric Furst, University of Delaware

The discovery resulted from collaboration between researchers from Yale University and the University of Delaware. The Yale team developed an efficient and reliable method for making large quantities of identical nanoparticles that are 10 times smaller than previous particles. The Delaware team created a way to organize the particles into a crystalline structure, using an electric field. The researchers found that, unlike spherical nanoparticles, dumbbell-shaped particles readily align in the presence of an external field.

Editor's Note: Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation. See the Research in Action archive.