An ancient mechanism at molecular scale
Scientists have built an electrically powered molecular motor inspired by Archimedes’ screw, a device traditionally used to lift water. In the new work, electrical current passes through a spiral-shaped molecule suspended between gold electrodes, driving the molecule to rotate.
The researchers report that the motor can rotate in either direction, with the direction controlled by changing the applied voltage. They also observed that its motion can increase electrical conductivity by up to 100 times, a result that could be relevant to future molecular-scale electronic components.
How the molecular motor works
The central component is a specially designed spiral molecule developed by a team at the University of Copenhagen. It is small enough to connect to gold surfaces through sulfur atoms. Researchers at the Weizmann Institute of Science placed individual molecules between gold tips sharpened to atomic dimensions.
By adjusting the distance between the electrodes, the team could stretch or compress the molecule while measuring the electrical behavior of the junction. Electrons travelling through the spiral-shaped structure were used not only to probe it, but also to induce rotational movement.
The work differs from earlier electrically powered molecular motors, which operated on surfaces and relied on a scanning-tunneling-microscope tip to provide the driving interaction. Here, the molecular component forms part of an electrical circuit between the two gold contacts.
Conductivity changes with movement
The reported conductivity change is a central part of the result. As the molecule rotates, its ability to conduct electricity changes dramatically. The source describes increases of as much as 100-fold, linking mechanical motion at the molecular level with a measurable electronic signal.
That coupling is significant because molecular electronics aims to use individual molecules as functional circuit elements. A molecule that can change its conductance in response to controlled motion could eventually support switches, sensors, or other components far smaller than conventional semiconductor devices.
The research should not be read as an immediate route to commercial electronics. The experiment uses carefully prepared single-molecule junctions and gold electrodes under laboratory conditions. But it demonstrates a controllable mechanism in which electrical input drives molecular rotation and the resulting configuration alters electrical transport.
A step toward functional molecular machines
Molecular machines have long been a target for chemists and physicists seeking to reproduce, in artificial systems, some of the motion-producing functions found in living cells. Biological molecular motors use energy to create movement; researchers have worked for decades to make synthetic versions with defined mechanical behavior.
The Archimedes’ screw concept provides an intuitive picture for the new device. In its macroscopic form, a rotating spiral moves water. At molecular scale, the spiral design instead provides a path through which electrons can travel, while the passage of current is associated with rotational motion.
The ability to reverse rotation by switching voltage adds an important degree of control. Reversibility could matter wherever a molecular device must be set between more than one functional state, rather than simply activated once.
What comes next
Further work will be needed to establish how robustly the effect can be reproduced, how it behaves across larger sets of devices, and whether related designs can operate in practical electronic environments. The current finding nevertheless offers a compact demonstration of electromechanical control at the scale of a single molecule.
For molecular electronics, the result points to a possible design principle: make the molecular structure itself do mechanical work, then use the resulting shape change to tune the flow of charge. If that principle can be engineered reliably, it could help bridge the gap between molecular motion and useful electronic function.
This article is based on reporting by Science Daily. Read the original article.
Originally published on sciencedaily.com
