Electric Current Spins a Helical Molecule and Boosts Its Conductance

Researchers have built a molecular-scale rotary machine in which electric current does the driving: a single helicene molecule, suspended between two electrode tips, spins in response to an applied voltage, and its rotation in turn makes the molecule a better conductor. The study, published in Nature, reports that the cyclic molecular motion shows complete directional preference, with the rotation direction reversing when the voltage polarity is flipped. Above a certain voltage threshold, the current flowing through the rotating molecule is significantly enhanced, and the onset of that enhancement can be tuned by stretching or compressing the helical molecule within the junction.

The design borrows from one of humanity’s oldest machines. Archimedean screws, with their helical blades, have been used for water pumping for more than two thousand years and more recently as turbines in hydroelectric power stations. Helical-blade geometry is also found in chiral molecules and nanostructures, and previous theoretical work had proposed that injecting electric current into such structures could generate torque-mediated rotation. What distinguishes the new experiment is that the predicted interplay between rotation and charge transport is now observed directly in a working single-molecule junction, with effects that were absent in earlier helical molecular junctions, a difference the authors attribute to structural and operational differences between the setups.

The experimental observations and the theoretical interpretation must be kept distinct. On the measured side, the team suspended a helicene molecule between two electrode tips and applied a voltage, detecting cyclic molecular motion with 100 percent directional preference that could be inverted by reversing the voltage’s polarity. They also measured a significant enhancement of the current above a threshold voltage, with the threshold position adjustable by mechanically stretching or compressing the helical molecule. These are direct observations on a single-molecule junction.

On the interpretive side, calculations indicate that molecular rotation driven by current-induced forces explains both the observed cyclic motion and the current enhancement. The mechanism predicts a transition from stepwise to continuous rotation at a threshold voltage, and it accounts for the current increase as a consequence of rotation: once spinning, the molecule can adopt highly conducting configurations that are not accessible when it is at rest. In other words, the act of rotation itself opens conduction channels that a stationary helicene cannot reach, coupling the mechanical and electronic degrees of freedom of the junction.

The authors present the system as a prototype for a new class of torque-driven molecular machines, combining perfect rotor unidirectionality with significant current modulation. Because the rotation direction is set entirely by the voltage polarity and the conductance depends on the rotational state, the junction functions simultaneously as a motor and as a readout of its own motion, with the molecular geometry acting as the control element. The tuning of the enhancement onset by stretching or compressing the molecule suggests that the mechanical conformation of the junction is an active parameter in the device’s operation rather than a fixed background condition.

As with any single-molecule experiment, the reported behavior is specific to the helicene junction studied, and the theoretical account, while consistent with the observations, remains a calculation-based explanation of the measured cyclic motion and current enhancement. The work appears in Nature as an early-release, peer-reviewed, accepted version carrying a permanent DOI, subject to further editorial edits before the final version of record. Within those limits, the study demonstrates that current-induced forces can drive a chiral molecular rotor with complete directional control, and that the resulting rotation measurably enhances charge transport through the molecule, establishing a concrete experimental platform for torque-driven molecular machinery at the single-molecule scale.

Subject of Research: A current-driven helicene molecular rotor whose rotation enhances conductance in a single-molecule junction

Article Title: Current-Driven Molecular Machine with Rotation-Enhanced Conductance

Article References: Singh, A. K., Martin, L., Sršen, M., Guttesen, F. S., Hu, B.-Z., Ito, Y., Pedersen, S. K., Kamounah, F. S., Pauly, F., Pittelkow, M., Lü, J.-T., Hedegård, P., & Tal, O. (2026). Current-Driven Molecular Machine with Rotation-Enhanced Conductance. Nature. https://doi.org/10.1038/s41586-026-11312-x

Image Credits: AI Generated

DOI: 10.1038/s41586-026-11312-x

Keywords: molecular machines, helicene, molecular electronics, single-molecule junction, current-induced forces, molecular rotor, conductance, torque, chirality, nanotechnology, Current-Driven, Molecular