Rice University researchers have shown that tiny, sharply curved wrinkles in graphene can dramatically alter the material's electrical properties — providing direct evidence for flexoelectricity, a phenomenon in which a material generates an electric charge when it bends unevenly. The findings are published in Advanced Materials.
Graphene is a sheet of carbon just one atom thick. The wrinkles examined in the study are bent into spaces smaller than a billionth of a meter, where extreme curvature shifts electrons slightly to one side, creating two opposite electrical sides 'like the ends of a tiny battery,' said lead author Sathvik Ajay Iyengar, a former Rice doctoral student.
Using specialized microscope probes, Raman spectroscopy and computer simulations, the team found that the sharply curved wrinkles acted like rows of tiny electrical speed bumps: once about one volt was applied, they consistently produced an electrical current, closely matching the models. The response depended on the sharpness of the wrinkle, not its height — the resulting charge separation, or polarization, was between 100,000 and 10 million times stronger than in much larger flexoelectric systems.
'Our work shows that even an ordinary wrinkle can become an extraordinary electronic feature when viewed at the atomic scale,' said Pulickel Ajayan, the study's co-corresponding author. 'By demonstrating that geometry alone can reshape electrical behavior in graphene, we open a new pathway for designing materials whose properties can be controlled through structure rather than chemistry.'
The discovery confirms a prediction made in 2008 by theoretical physicist Vincent Meunier, now at Penn State, who proposed that sharply bending graphene could rearrange its electrons and produce an electrical response. The findings could one day lead to more sensitive sensors and ultrathin electronic devices whose behavior is tuned by shape alone — no added chemicals or materials required.
