Graphene is a two-dimensional wonder-material that has the potential to change the face of engineering. It is made of a single layer of carbon atoms, is strong, transparent, and conducts electricity excellently. It has potential in a wide range of applications, such as reinforcing and lending electrical properties to plastics; creating denser, faster integrated circuits, and even building better touch screens.
Although it seems like a fairytale come true, there is one slight problem that has prevented graphene from world domination—it literally falls apart at large-scale production. “Normally, graphene is produced in small flakes, and even these small flakes have defects,” said Alexander Yarin, researcher and distinguished professor in the Department of Mechanical and Industrial Engineering. What is worse is when you try to deposit them [the graphene flakes] onto a large-scale area, the defects increase, and graphene’s useful properties—its “magic”—are lost, he said.
If the graphene flakes could somehow “stick together” on a large scale, then it could finally be used for its incredible properties, so Yarin attempted to solve this problem of the graphene flakes forming a consistent layer without any clumps or cracks. He quickly reached out to collaborate on a study with Sam S. Yoon, professor of mechanical engineering at Korea University. Yoon had been working with a unique kinetic spray deposition system that exploits the supersonic acceleration of droplets through a Laval nozzle. Although Yoon was working with different materials, Yarin believed Yoon’s method might be used to deposit graphene flakes into a smooth layer.
The idea was to use the supersonic spray system to produce very small droplets of graphene suspension, which would disperse evenly, evaporate rapidly, and reduce the tendency of the graphene flakes to aggregate.
But to the researchers’ surprise, when they applied the spray method, defects inherent in the graphene flakes disappeared. The result was a higher quality graphene layer, as found in the analysis by another collaborator, Suman Sinha-Ray, senior researcher at United States Gypsum and UIC adjunct professor of mechanical and industrial engineering.
The energy of the impact stretched the graphene and restructured the arrangement of its carbon atoms into the perfect hexagons of flawless graphene—“healing” the defects and creating a strong, flawless layer of graphene. “Imagine something like Silly Putty hitting a wall—it stretches out and spreads smoothly,” said Yarin. “That’s what we believe happened with these graphene flakes. They hit with enormous kinetic energy, and stretched in all directions.
“We’re tapping into graphene’s plasticity — it’s actually restructuring.”
Other attempts to produce graphene without defects or to remove flaws after manufacture have proved difficult and prohibitively expensive, Yarin said.
The new method of deposition, which allows graphene to “heal” its defects during application, is simple, inexpensive, and can be performed on any substrate with no need for post-treatment, he said. Yarin, who was recently awarded two grants from the Nonwovens Institute of North Carolina State University to continue this successful research, and his Korean colleagues hope to continue their successful collaboration and foster the development of industrial-scale applications of graphene.
Jung-Jae Park, Jung-Gun Lee and You-Hong Cha of Korea University; Sang-Hoon Bae and Jong-Hyun Ahn of Yonsei University; and Yong Chae Jung and Soo Min Kim of the Korea Institute of Science and Technology are co-authors on the paper.
Initial support for the collaboration between Yarin’s group at UIC and Yoon’s group at Korean University was provided by the Office of International Affairs Nuveen International Development Fund at UIC and by Korea University.
This article was adapted from the UIC News release linked below, and has been extensively written about and re-published. See the links, below.
The study is available online in the journal Advanced Functional Materials.
In addition, a number of news sites have quoted Professor Yarin, and republished the UIC News release.
To read more about Professor Yarin’s research on graphene layers:
GizMag: Scientists create “spray-on graphene”
Wired UK: Supersonic spray gun produces ‘flawless’ layer of graphene
Extreme Tech: Researchers create high-quality graphene with shockingly simple supersonic spray system
Gizmodo: New method for spray-on graphene makes the supermaterial even stronger
Overclockers Club: Easier means of getting graphene into useful substrate
Compilers (re-publication of the release):