These Color-Changing Graphene Bubbles are Mesmerizing
Dutch engineers at Delft University of Technology have discovered what could be a new type of display. These bubbles of graphene change color while expanding and contracting.
These mechanical pixels could create flexible screens more durable than that of current LEDs. The team collaborated with Graphnea in Spain to organize the 13-micrometer wide, balloon-like pixels. They then covered them with a double layer of graphene just two atoms thick. The graphene closed air within the cavities.
The color change came as a surprise and a slight disappointment, according to Santiago Cartamil-Bueno, a PhD student at Delft.
“At first, I was disappointed since I was researching these devices to see if they might have a function as sensors," Cartamil-Bueno said. “Seeing the colours under a microscope, I realized that the devices were not homogeneous, which is bad if you are trying to create a sensor.”
Samer Houri, leader of the research teams, said they observed Newton rings and then realized the nanodevices were behaving like balloons. The pressure differences between cavity and the outer atmosphere caused the membrane to push down toward the bottom of the cavity.
The color change came from difference in lightwaves getting reflected from the membrane's bottom to its top. When the membranes get closer to the silicon, they look blue. When they go upwards away from the silicon, they turn blue.
“These devices provide a means to implement display technology based on interferometric modulation," said Cartamil-Bueno.
However, the team has several obstacles to overcome in trying to produce more of these graphene balloons. They can't create pure colors just yet, despite trying to control them electrically.
“I have seen the whole rainbow of colors, it’s quite a natural effect,” said Cartamil-Bueno in an interview with The Verge. “But you cannot get clean colors like pure red or pure blue.”
Also, the team doesn't know the best way to expand the size of this 'display' to modern LED screens. The changes seen so far have been observed under a microscope.
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Via Delft News