U.S. and Korean researchers say they've developed a simple and inexpensive way to create films of graphene, a wonder material comprising a single layer of carbon atoms with a wide range of applications.
Those applications could include faster and better integrated circuits, improved touch screens, and stronger, electrically-conductive plastics, they say.
In the technology developed by scientists at the University of Illinois in Chicago and at Korea University, a spray method creates films or layers of high quality graphene that can be applied to a number of substrates.
A current roadblock to the almost unlimited potential uses of graphene is the difficulty of scaling up production of the material from the microscope level to large-scale applications while managing to avoid creating defects, the researchers said.
"Normally, graphene is produced in small flakes, and even these small flakes have defects," Illinois researcher Alexander Yarin says. "When you try to deposit them onto a large-scale area, defects increase, and graphene's useful properties are lost."
Yarin turned to a colleague, Sam S. Yoon, a mechanical engineering professor of Korea University who had been experimenting with a high-tech spray system that accelerated droplets at supersonic speed through a special spray nozzle that mimics the output end of a jet or rocket engine.
Yoon and Yarin found the supersonic spray deposition system could create extremely tiny droplets of a graphene suspension that dispersed evenly over a substrate, drying rapidly and reducing the propensity for the flakes of graphene to clump up or leave spaces.
In the spray technology, with its miniscule droplets, the tendency for inherent defects to occur in the flakes disappeared, they said.
The energy in the droplets' impact with the substrate was stretching the material and arranging the carbon atoms to form hexagons of perfect graphene, they said.
"Imagine something like Silly Putty hitting a wall -- it stretches out and spreads smoothly," says Yarin. "That's what we believe happens with these graphene flakes. They hit with enormous kinetic energy, and stretch in all directions.
"We're tapping into graphene's plasticity -- it's actually restructuring."
The technology, in which the graphene "heals" its own defects during its application, can be used for any substrate without need of any kind of post-application treatment, the researchers said.
Yarin and Yoon have reported the details of the technology in the journal Advanced Functional Materials.
