Summary
Researchers report that voltage can drive cyclic rotation in a helicene molecule held between gold electrodes. The rotation changes how readily current passes through the junction, and reversing voltage polarity reverses the preferred direction of motion.
A peer-reviewed study published in Nature on 22 October 2026 reports a molecular rotor driven by electric current. The researchers placed a helicene molecule between two gold electrode tips and found that an applied voltage induced cyclic motion. Reversing the voltage polarity reversed the preferred direction of rotation.
The result brings a familiar mechanical idea—the helical form of an Archimedean screw—to a single-molecule junction. But the molecule does not pump water. Instead, its motion is coupled to electrical transport: as it rotates, the ease with which current passes through the junction changes.
How voltage drives the rotor
Helicenes have a twisted, helical shape. In this experiment, the molecule was held between the electrodes while current flowed through the junction. The paper reports that the voltage drove cyclic molecular motion with “100% directional preference,” which describes the preferred direction of rotation, not an energy-conversion efficiency. Changing the polarity switched that direction.
The researchers also found that current through the rotating molecule increased significantly above a voltage threshold. Stretching or compressing the helical molecule shifted where this enhancement began. That mechanical adjustment changes the conditions under which the junction starts to show the higher-current behaviour.
The team used calculations to explain the observations. Their model attributes both the rotation and the current increase to forces generated by the current. As the molecule turns, it can adopt configurations that conduct electricity more readily than configurations available when it is stationary. Rotation therefore affects conductance—the ease with which electrical current flows—while the current helps drive the rotation.
A machine whose motion changes its electrical signal
The calculations predict a change from stepwise rotation, in which the rotor moves between preferred positions, to continuous rotation above a threshold voltage. In that account, the current rises as rotation lets the molecule access more highly conducting configurations. The paper presents this mechanism as an explanation for the experimentally observed cyclic motion and enhanced current.
The significance is the coupling of electrical input, molecular motion and electrical output in one junction. It offers a prototype for studying torque-driven molecular machines: current supplies the drive, and the rotor’s movement modulates the current. The reported system remains a single-molecule experimental junction, rather than a practical pump or an integrated device; its immediate contribution is a demonstration of controllable molecular motion and conductance in the same structure.