Researchers from the University of California at Berkeley and Rice University have discovered that when stress is applied, graphene does not rip apart randomly like paper but follows the least resistance path resulting in new edges that provide remarkable properties to the wonder material.
Boris Yakobson, Rice University's Karl F. Hasselmann Professor of Mechanical Engineering and Materials Science and Professor of Chemistry. (Photo: Rice University)
According to Boris Yakobson from the Karl F. Hasselmann Chair of Engineering, Professor of Chemistry and Professor of Mechanical Engineering and Materials Science, the research paves the way to control the electrical properties of graphene, as they vary with the different edges of the material.
The researchers at Rice University developed computer simulations that recreate the type of ripping detected by the researchers at the University of California at Berkeley using an electron microscope. The California research team observed that the edges formed due to the cracking of graphene flakes were in zigzag or armchair forms. According to the team, stress is handled by graphene based on its molecular forces.
Armchair-edged graphene is a semiconductor, while zigzag-edged graphene is metallic in nature. Since the edges of graphene manipulate its electrical properties, the shape of the edges caused by the ripping of graphene is the key area of the research, according Yakobson. His team discovered that graphene looks for a path that consumes minimum amount of energy. The California team discovered that fractures in a graphene flake strictly followed the paths that were 30° apart from one another. This 30° separation decides the armchair or zigzag shape of the edges of the material, noted Yakobson.
The researchers also discovered that cracks in graphene along grain boundaries also followed the same rules. The research demonstrated that graphene can be ripped in a well-defined direction, which is significant for electronics, Yakobson concluded.