RESOLVING THE LEDGER
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Add as preferred source Rice University researchers have shown that tiny wrinkles in graphene can change the material's electrical properties, providing evidence for flexoelectricity, a phenomenon in which a material generates an electric charge when it bends unevenly. The findings are published in Advanced Materials .
The discovery suggests scientists may be able to control electricity in atomically thin materials by changing their shape instead of adding new chemicals or materials. The approach could one day lead to more sensitive sensors and ultrathin electronic devices.
"Our work shows that even an ordinary wrinkle can become an extraordinary electronic feature when viewed at the atomic scale," said Pulickel Ajayan, the Benjamin M. and Mary Greenwood Anderson Professor of Engineering and co-corresponding author of the study. "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."
Graphene is a sheet of carbon just one atom thick. In this work, the team examined naturally formed wrinkles with bends compressed into spaces smaller than a billionth of a meter, where the extreme curvature can shift electrons toward one side of the material.
"Imagine bending a flexible ruler, except the bend is squeezed into a space smaller than a billionth of a meter," said Sathvik Ajay Iyengar, a former Rice doctoral student and lead author of the study. "At that scale, the electrons in graphene shift slightly toward one side, creating two opposite electrical sides like the ends of a tiny battery."
The research team used specialized microscope probes to measure the wrinkles' shape, local electrical energy and electrical current. They also used Raman spectroscopy, a laser-based technique that reveals how atoms are stretched or compressed, along with computer simulations that predicted how bending changes the movement of electrons. Comparing sharply curved wrinkles with nearby flat graphene allowed the team to isolate the effects of curvature.
"Earlier studies often examined gentler bends or relied on external pressure, making this subtle effect difficult to separate," Iyengar said. "Comparing the sharply curved wrinkles with flat graphene allowed us to clearly identify the role of extreme curvature."
The researchers found that the wrinkles acted like rows of tiny electrical speed bumps. Their sharply curved tips changed the local electrical energy and consistently produced an electrical current when a voltage of about 1 volt was applied, closely matching predictions from the computer models.
The electrical response depended on the sharpness of the wrinkles rather than their height. The researchers estimated that the resulting electrical charge separation, called polarization, was between 100,000 and 10 million times stronger than in much larger flexoelectric systems. Polarization is the separation of positive and negative electrical charges within a material.
"The sharpness of the wrinkle turned out to be much more important than its overall size," Iyengar said. "That tells us we can potentially tune electrical behavior by carefully controlling curvature at the nanoscale."
The discovery dates to 2008, when theoretical physicist Vincent Meunier predicted that sharply bending graphene could rearrange its electrons and produce an electrical response. Meunier, now the P. B. Breneman Chair and head of the Department of Engineering Science and Mechanics at Pennsylvania State University, is a co-corresponding author of the study. At the time, measuring the effect across bends only a few atoms wide was extremely difficult.
Years later, Iyengar revisited data he had collected with Manoj Tripathi, a co-corresponding author at the University of Sussex and now at South Dakota Mines, and found unusual electrical signals at the sharpest graphene wrinkles. He brought the findings to Meunier, who had co-advised his doctoral work.
"When Sathvik showed me the measurements he and Manoj had collected, we realized that the unusual signals could provide an experimental connection to an idea we had predicted many years earlier," Meunier said. "Bringing the experiments and atomic-scale calculations together allowed us to test that connection directly."
The researchers said the findings could help scientists explore whether controlling the curvature of graphene wrinkles could provide a way to adjust the material's electrical behavior. That approach could eventually support the development of more sensitive sensors and ultrathin electronic devices.
"Nature already creates these tiny wrinkles for us," Iyengar said. "Understanding how they influence electrical behavior gives scientists another tool for designing future technologies using the structure of a material itself."
Sathvik Ajay Iyengar et al, Sub‐Nanometer Curvature Unlocks Quantum Orbital Flexoelectricity in Graphene, Advanced Materials (2026). DOI: 10.1002/adma.202518224
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