The new breed of display screens uses flexible fins, varying temperatures and liquid droplets that can be arranged in various orientations to create images. The control is precise enough to achieve complex motions, like simulating the opening of a flower bloom. Image: Sameh Tawfick.Flexible displays that can change color, convey information and even send veiled messages via infrared radiation are now possible, thanks to new research from the University of Illinois at Urbana-Champaign. Engineers inspired by the morphing skins of animals like chameleons and octopuses have developed capillary-controlled robotic flapping fins to create switchable optical and infrared light multipixel displays that are 1000 times more energy efficient than light-emitting devices.
The new study led by mechanical science and engineering professor Sameh Tawfick demonstrates how bendable fins and fluids can simultaneously switch between straight or bent and hot and cold by controlling the volume and temperature of tiny fluid-filled pixels. Varying the volume of the fluids within the pixels can change the directions in which the flaps flip – similar to old-fashioned flip clocks – while varying the temperature allows the pixels to communicate via infrared energy. The engineers report their work in a paper in Science Advances.
Tawfick’s interest in the interaction of elastic and capillary forces – or elasto-capillarity – started with the basic science of hair wetting when he was a graduate student and led to his research in soft robotic displays at Illinois.
“An everyday example of elasto-capillarity is what happens to our hair when we get in the shower,” Tawfick explained. “When our hair gets wet, it sticks together and bends or bundles as capillary forces are applied and released when it dries out.”
In the lab, the team created small boxes, or pixels, a few millimeters in size that contain fins made of a flexible polymer. These fins bend when the pixels are filled with fluid and then drained using a system of tiny pumps. The pixels can have single or multiple fins and are arranged into arrays that form a display to convey information.
“We are not limited to cubic pixel boxes either,” Tawfick said. “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.”
The study reports that another feature of the new displays is their ability to send two simultaneous signals – one that can be seen with the human eye and another that can only be seen with an infrared camera.
“Because we can control the temperature of these individual droplets, we can display messages that can only be seen using an infrared device,” Tawfick said. “Or we can send two different messages at the same time.”
However, there are a few limitations to the new displays. While building them, the team found that the tiny pumps needed to control the pixel fluids were not commercially available, and the entire device is sensitive to gravity – meaning that it only works in a horizontal position.
“Once we turn the display by 90°, the performance is greatly degraded, which is detrimental to applications like billboards and other signs intended for the public,” Tawfick said. “The good news is, we know that when liquid droplets become small enough, they become insensitive to gravity, like when you see a rain droplet sticking on your window and it doesn’t fall. We have found that if we use fluid droplets that are five times smaller, gravity will no longer be an issue.”
The team said that because the science behind gravity’s effect on droplets is well understood, it will provide the focal point for their next application of this emerging technology.
Tawfick said he is very excited to see where this technology is headed because it brings a fresh idea to a big market space of large reflective displays. “We have developed a whole new breed of displays that require minimal energy, are scaleable and even flexible enough to be placed onto curved surfaces.”
This story is adapted from material from the University of Illinois at Urbana-Champaign, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.