Summary
Researchers report a helicene molecule that rotates directionally when voltage is applied, with the direction reversing when voltage polarity changes. Above a threshold, rotation enhances current through the molecule, and stretching or compressing it tunes that threshold.
Researchers have built a molecular-scale machine in which electric current drives rotation and the rotation, in turn, increases current through the molecule. In a Nature paper published on 22 October 2026, the team reports that applying voltage to a helicene held between two electrode tips produces cyclic motion with 100% directional preference. Reversing the voltage polarity reverses the preferred direction. Above a voltage threshold, current through the rotating molecule rises significantly; stretching or compressing the molecule shifts where that increase begins.
The work links a molecule’s mechanical motion to its electrical conductance in a single junction. The authors describe the device as a prototype for torque-driven molecular machines. The Nature page identifies the paper as peer-reviewed accepted research presented in an early-access version that will be replaced by the final Version of Record.
How voltage drives the molecular rotor
Helicenes are molecules whose structure twists into a helix. The researchers suspended a functionalized [13]helicene molecule between gold electrode tips, forming a single-molecule junction. When voltage is applied, current flows through the junction. The team reports that this electrical operation drives the molecule through cyclic motion rather than leaving it in a fixed orientation.
A helical shape can couple electrical forces to rotation: the current passing through the molecule can exert torque on its structure. The experiments showed a strong directional preference, and changing the sign of the applied voltage changed the direction. This polarity control is a defining feature of the reported molecular machine—not simply motion occurring alongside an electrical measurement.
The researchers used calculations to explain the motion through forces induced by current. Their model predicts that rotation can proceed in steps between preferred molecular positions at lower drive, then become continuous beyond a threshold voltage. This predicted change in how the rotor moves provides a way to understand the threshold behaviour reported in the measurements.
Rotation changes how well the molecule conducts
The molecule’s motion also affects its electrical properties. The paper reports a significant increase in current above a voltage threshold. According to the calculations, rotation lets the molecule adopt configurations with higher conductance—configurations that are not accessible when it is at rest. Conductance describes how readily electrical current passes through a material or device at a given voltage.
Changing the molecule’s shape by stretching or compressing it tunes the onset of the current enhancement. That result connects the junction’s mechanical arrangement to its electrical response: the threshold is not fixed independently of the rotor’s geometry.
Together, the results describe a feedback between motion and transport. Current supplies the torque that drives rotation, while rotation changes the configurations available for electrons to pass through the molecule. The demonstration is a molecular-junction prototype, not a macroscopic motor or a practical pumping device; its significance is in showing how controlled molecular motion and electrical conductance can be coupled in one system.