IIT Madras Physicist's Nature Study Shows a Voltage-Driven Molecular Rotor Can Boost Current Up to 100-Fold
A Nature paper with IIT Madras physicist Anil Kumar Singh as a corresponding author shows that a spiral helicene molecule between gold electrodes rotates in one direction under voltage, and that the rotation raises its conductance by up to about 100 times. The result points to a new way of switching single-molecule devices.
Can a single molecule work as a switch? A paper in Nature, published on 22 October 2026, adds a new possibility. The authors trapped one spiral-shaped molecule between two gold electrodes, applied a voltage and watched it rotate in one direction. As it rotated, the current flowing through it rose sharply, by up to about 100 times according to reports on the study.
The paper is titled "Current-Driven Molecular Machine with Rotation-Enhanced Conductance". Its experimental work was anchored at IIT Madras. Anil Kumar Singh of the institute's Department of Physics is a corresponding author and is described as the principal experimental contributor. The collaboration included researchers from India, Israel, Germany, Denmark and China, with co-authors at institutions including the Weizmann Institute of Science and the University of Augsburg.
The experiment
The molecule at the centre of the study is a helicene. Helicenes are made of fused aromatic rings that twist into a corkscrew instead of lying flat, so they have a built-in handedness, like a left or right screw thread. That shape is what makes them interesting as molecular machines.
The team used a mechanically controllable break junction. In this technique, a thin gold wire is stretched until it breaks, leaving a gap a few atoms wide, and a single molecule can bridge that gap. When they applied a voltage across the helicene, the molecule moved through a repeating, cyclic sequence of shapes: it rotated. Reversing the polarity of the voltage reversed the direction of rotation. The paper's abstract reports complete (100%) directional preference, which can be inverted by switching the polarity.
The more striking result concerns current. Above a threshold voltage, the current through the junction jumped sharply. Measurements and theoretical calculations indicated that the rotation lets the molecule pass through shapes that conduct electricity much more easily. In other words, motion and conductance are linked: the electrical current drives the rotation, and the rotation in turn opens a better path for that current.
Why it matters
For decades, molecular electronics has promised circuits built from components the size of a single molecule, far smaller than today's best silicon transistors. One persistent problem has been control: getting a molecule to switch reliably between a low-conduction "off" state and a high-conduction "on" state using only electrical signals. A molecule whose conductance rises when an applied voltage makes it rotate points to a new kind of switching mechanism. Here the change comes from mechanical motion inside the molecule, not just changes in its electronic states.
The work also contributes to the field of artificial molecular machines, recognised by the 2016 Nobel Prize in Chemistry. Most such machines are driven by light or chemical fuel. A rotor that runs on electrical current and reports its own motion through a change in conductance is easier to imagine connecting to electronic circuits.
For India, the paper is a reminder that frontier nanoscience is being done in Indian laboratories, not just consumed by them. Single-molecule break-junction experiments need precise mechanical control, very low-noise electronics and cryogenic equipment. Having an Indian group lead the experimental side of a Nature paper in this area shows the country's growing ability in fundamental device physics, which future nanoelectronics and quantum-device programmes will draw on.
The caveats
Singh has described the result as a proof of principle. The experiments were carried out at cryogenic temperatures, and more research is needed to show reliable operation in practical conditions, including at or near room temperature. The "up to 100-fold" figure is a maximum reported in press coverage of the study, not a typical value. Applications such as molecular switches or nanoscale motors remain possibilities, not demonstrated devices. Single-molecule junctions also vary a lot from one junction to the next, which any engineering use would have to overcome.
What the study does establish is a clear, reversible, voltage-controlled link between motion and conduction in a single molecule. That is a useful new tool for researchers trying to build electronics from individual molecules.
Sources
- https://www.nature.com/articles/s41586-026-11312-x
- https://www.dtnext.in/news/chennai/iit-madras-scientist-part-of-team-demonstrating-electrically-driven-molecular-rotation
- https://www.deccanchronicle.com/southern-states/tamil-nadu/iit-m-faculty-makes-key-inputs-to-global-study-on-molecular-electronics-1998453
- https://www.etvbharat.com/en/technology/iit-madras-faculty-contributes-to-multinational-study-showing-molecular-motion-might-help-control-nanoscale-electronic-devices-enn26102404706
- https://www.electronicsforu.com/news/molecular-motion-points-towards-future-nanoscale-electronics