This Fin-Flapping Elasto-Capillary Display Draws 1,000th the Power of a Traditional LCD Panel

Researchers at the University of Illinois at Urbana-Champaign and Ajou University have come up with an entirely new concept for building flexible, high-efficiency displays — inspired by the color-changing talents of chameleons and octopuses and driven by shifting fins and varying temperatures to harness elasto-capillarity.

"An everyday example of elasto-capillarity is what happens to our hair when we get in the shower," explains project lead Sameh Tawfick, professor of mechanical science and engineering at Urbana-Champaign. "When our hair gets wet, it sticks together and bends or bundles as capillary forces are applied and released when it dries out."

The display developed by the team, directly inspired by the color-changing skins of animals like chameleons and octopuses, uses bendable fins with temperature control capabilities to alter the volume of liquid in each picture element (pixel) of the display. Increase the volume, and the pixel flips from clear to opaque — similar to the operation of a vintage flip-digit clock.

"We are not limited to cubic pixel boxes," Tawfick claims of the display's flexibility, both literally and metaphorically. "The fins can be arranged in various orientations to create different images, even along curved surfaces. The control is precise enough to achieve complex motions, like simulating the opening of a flower bloom."

One interesting side-effect of giving each pixel the ability to differentiate itself from its neighbors by both light reflection and heat emission is that a single display can encode two entirely different messages: one visible to the naked eye and the other only visible under infrared sensors. "Because we can control the temperature of these individual droplets, we can display messages that can only be seen using an infrared device," Tawfick explains. "Or we can send two different messages at the same time."

The biggest advantage of the technology, though, is undoubtedly its energy efficiency: the team estimates that the elasto-capillary display draws around a thousandth the energy of a traditional liquid crystal display. The only problem: it relies on compact pump technology not yet commercially available and only operates when flat, with the liquid forced to fight gravity when in the vertical orientation. "We have found," Tawfick says on the latter problem, "that if we use fluid droplets that are five times smaller, gravity will no longer be an issue."

The team's work has been published under open access terms in the journal Science Advances.