Researchers measured an electrical response at exceptionally sharp wrinkles in graphene, a single layer of carbon atoms, according to a Penn State-authored report published by SciTechDaily. The results provide experimental support for a prediction made nearly 20 years ago that sharply bending graphene could rearrange its electrons.
The effect is called flexoelectricity: uneven bending separates electrical charges within a material. In graphene, the report explains, extreme curvature can shift electrons toward one side of the sheet, creating regions of opposite charge. Vincent Meunier and Sergei V. Kalinin made the earlier prediction. Lead author Sathvik Ajay Iyengar and collaborators examined naturally occurring wrinkles whose sharpest bends spanned only a few atoms. “The sharpness of the wrinkle turned out to be much more important than its overall size,” Iyengar said.
Using microscopy, Raman spectroscopy and modeling, the team compared sharp wrinkles with nearby flat graphene. The wrinkle tips changed local electrical energy and consistently showed current when approximately one volt was applied, the report says. The researchers estimated that polarization at the sharpest bends was between 100,000 and 10 million times stronger than that associated with much larger, gentler bends.
The report describes more sensitive sensors and electronic components as possible future uses. The measured current required an external voltage; it was not a demonstration of electricity generation without one.
