A machine inspired by an invention more than 2,000 years old has been recreated at a scale almost impossible to imagine: a single molecule. Researchers have demonstrated an electrically powered molecular motor that can rotate in either direction when the voltage is changed. The work could help scientists develop electronic components and machines at extremely small scales.

An ancient screw becomes a nanoscale machine

The design takes inspiration from the Archimedes screw, a spiral-shaped device traditionally used to move water from a lower level to a higher one. At ordinary sizes, the screw turns to transport liquid. In the new research, scientists adapted the spiral concept into a molecule that responds to electrical current.

The molecule is only a few millionths of a millimeter long. Researchers connected it between two extremely fine gold electrodes. When they applied an electrical voltage, the molecule began rotating. Reversing the voltage polarity changed the direction of rotation, giving the team a way to control the movement.

Why electricity makes it turn

The basic idea is that electrons moving through the spiral-shaped molecule transfer angular momentum to its structure. That transfer produces rotation, somewhat like moving air turning a wind turbine. The molecule’s shape matters: its spiral geometry influences how it responds to the flow of electrons.

The researchers describe the work as a significant step because the motor is driven directly by electrical current, is connected to two metal electrodes and can rotate in a controllable direction. Earlier electrically powered molecular motors had different limitations, including designs that relied on the tip of a scanning tunneling microscope to drive movement.

The surprising discovery: movement changes conductivity

The team noticed something unexpected while studying the motor: the rotating molecule could conduct electricity far more effectively than it did while stationary. Quantum-mechanical simulations helped explain why. Depending on the molecule’s position as it rotates, its ability to carry current can change dramatically—by as much as 100 times.

In simple terms, the molecule’s movement does not just use electrical energy to create motion. The motion also changes the path electricity can take through the molecule. Certain positions that are especially good at conducting current are less accessible when the molecule is at rest. Rotation allows the system to reach those positions.

Could this lead to smaller electronics?

The result is an early research milestone, not a ready-made component for phones or computers. Still, it gives researchers a new principle for designing molecular electronics: electrical current can create controlled movement, and that movement can in turn influence electrical current.

Potential future areas include molecular electronic devices, spintronics—which uses properties of electrons beyond their electrical charge—and systems that manipulate extremely small quantities of fluid. The work may also help scientists investigate how mechanical motion and electrical behavior interact at the atomic scale.

What happens next?

The next challenge is turning an elegant laboratory demonstration into something that can be reliably integrated into practical technology. Researchers will need to understand durability, repeatability, manufacturing methods and how multiple molecular devices might work together. Those are substantial engineering questions, and the current result does not mean molecular motors will soon replace conventional electronics.

But the idea is compelling: the same basic principle that once helped people move water can inspire a machine so small that its moving parts are individual molecules. It is a reminder that some of the biggest advances in engineering begin by rethinking familiar mechanisms at a completely different scale.

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Sources and research: University of Augsburg research summary via ScienceDaily · Original research paper in Nature: Current-Driven Molecular Machine with Rotation-Enhanced Conductance