As if its list of properties was not already impressive enough, materials scientists working with sophisticated computer models at Stanford University have added another useful trick to graphene’s repertoire: they have made it piezoelectric.
"We thought the piezoelectric effect would be present, but relatively small. Yet, we were able to achieve piezoelectric levels comparable to traditional three-dimensional materials," said Evan Reed, head of the Materials Computation and Theory Group at Stanford and senior author of the study. "It was pretty significant."
Piezoelectric materials are those which produce an electric charge when deformed – squeezed, bent or twisted in some way. But it works the other way, too: the shape of a piezoelectric material can be manipulated by applying an electric field.
Graphene is not naturally piezoelectric, but the Stanford team found that if doped with the right stuff, it could be.
From the University’s press release: They modeled [sic] graphene doped with lithium, hydrogen, potassium and fluorine, as well as combinations of hydrogen and fluorine and lithium and fluorine on either side of the lattice. Doping just one side of the graphene, or doping both sides with different atoms, is key to the process as it breaks graphene’s perfect physical symmetry, which otherwise cancels the piezoelectric effect.
The researchers also found that they could refine the piezoelectric properties of the graphene by carefully selecting where they added the dopant atoms. They hope the technique might help engineer piezoelectricity in nanotubes and other materials. According to the announcement, the work could have applications ranging from electronics, photonics, and energy harvesting to chemical sensing and high-frequency acoustics.
The work was published in the December 23 issue of the Journal ACS Nano.