Graphene forms electrically charged crinkles

Stacks of graphene tend to form saw-tooth crinkles when compressed. Those crinkles have an electrical charge that could be useful in studying DNA or guiding nanoscale self-assembly. Credit: Kim Lab / Brown University

Gently compressed stacks of graphene form sharp crinkles that carry an electric charge, which could be useful in nanoscale self-assembly and other applications. For more information see the IDTechEx report on graphene, 2D materials, and carbon nanotubes.

Researchers from Brown University have discovered another peculiar and potentially useful property of graphene, one-atom-thick sheets of carbon, that could be useful in guiding nanoscale self-assembly or in analyzing DNA or other biomolecules.

A study published in Proceedings of the Royal Society A demonstrates mathematically what happens to stacks of graphene sheets under slight lateral compression — a gentle squeeze from their sides. Rather than forming smooth, gently sloping warps and wrinkles across the surface, the researchers show that layered graphene forms sharp, saw-tooth kinks that turn out to have interesting electrical properties.

“We call these quantum flexoelectric crinkles,” said Kyung-Suk Kim, a professor in Brown’s School of Engineering and the paper’s senior author. “What’s interesting about them is that each crinkle produces a remarkably thin line of intense electrical charge across the surface, which we think could be useful in a variety of applications.”

The charge, Kim says, is generated by the quantum behavior of electrons surrounding the carbon atoms in the graphene lattice. When the atomic layer is bent, the electron cloud becomes concentrated either above or below the layer plane. That electron concentration causes the bend to localize into a sharp point and produces a line of electrical charge roughly one nanometer wide and running the length of the crinkle. The charge is negative across the tip of an upraised ridge and positive along the bottom of a valley.

Read more: Research shows graphene forms electrically charged crinkles

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