Scientists have developed an electrically powered motor using a single molecule, drawing inspiration from the ancient Archimedes screw. The molecular machine can rotate when an electric voltage is applied, and researchers can reverse its direction by changing the voltage polarity.The international research team also discovered an unexpected relationship between the molecule’s movement and its ability to conduct electricity. As it rotates, its electrical conductivity can increase by up to 100 times. The findings, published in the journal Nature, could help researchers develop electronic components and machines at the molecular scale.
How an ancient invention inspired a molecular motor
The design is based on the Archimedes screw, a spiral-shaped device traditionally used to move water from a lower level to a higher one. In the new research, scientists adapted the same helical principle to a molecule, replacing the movement of water with the flow of electrons.The molecule, measuring only a few millionths of a millimetre, was produced specifically for the study by a team led by Professor Michael Pittelkow at the University of Copenhagen. It was connected between two extremely fine gold electrodes using sulphur atoms.Researchers at the Weizmann Institute of Science in Israel stretched individual molecules between atomically fine gold tips. When they applied an electrical voltage, the molecule began rotating. Reversing the voltage polarity changed the direction of rotation.The researchers describe this as the first demonstration of a current-driven molecular motor that is attached to two metal electrodes and has a controllable direction of rotation.
How does electricity make a molecule rotate?
The movement is driven by electrons flowing through the helical molecule. As the electrons pass through its spiral structure, they transfer angular momentum to it, producing rotation.The researchers compare the process to a wind turbine, in which moving air transfers energy to rotating blades. In the molecular motor, however, the moving electrons provide the driving force.The molecule’s helical shape also determines the direction of rotation, much as the thread of a screw determines how it moves.Earlier electrically powered molecular motors had been demonstrated, but they relied on the tip of a scanning tunnelling microscope to drive movement while the molecule was on a surface. The new design operates through an electric current between two metal electrodes.
Why does rotation increase electrical conductivity?
One of the most interesting findings emerged when the researchers examined how the molecule’s movement affected its ability to conduct electricity.Professor Fabian Pauly’s research group at the University of Augsburg used quantum mechanical computer simulations to investigate the mechanism. The calculations showed that conductivity depends strongly on the molecule’s rotational position and can increase by up to two orders of magnitude, or around 100 times, during rotation.The researchers found that certain positions which the molecule tends to avoid when stationary are particularly effective at conducting electricity. Rotation makes these positions accessible, allowing more current to pass through the molecular structure.This means the relationship works in both directions: electricity drives the molecule’s movement, while that movement changes how effectively the molecule conducts electricity.
What could molecular motors be used for?
The findings could contribute to research into molecular electronic components, spintronics and microfluidic systems. Spintronics is a field of electronics that uses the spin of electrons, in addition to their electrical charge, to process or store information.Molecular machines could also help scientists investigate physical processes at extremely small scales. However, the latest research is a laboratory demonstration of a new operating principle, not a ready-to-use electronic component.Researchers will still need to investigate reliability, durability, manufacturing and the possibility of integrating multiple molecular machines into practical systems.The study involved researchers from institutions in Germany, Denmark, Israel and China, combining laboratory measurements with theoretical modelling. It demonstrates how a mechanism known for centuries can inspire a very different kind of machine, one that operates at the scale of an individual molecule.Source: University of Augsburg research announcement, October 27, 2026; research published in Nature under the title “Current-Driven Molecular Machine with Rotation-Enhanced Conductance”.
