Nearly 2,000 years ago, the Greek mathematician and inventor Archimedes created a novel device that could be used to carry water uphill. Known as the Archimedes screw, this ancient invention has now been scaled down by scientists to create a remarkable molecular motor that converts electrical current into controlled rotation.
Consisting of a spiral-shaped molecule suspended between a pair of gold electrodes, the new microscopic machine could pave the way toward a new generation of machines that operate at the smallest scales.
The breakthrough was reported by an international collaboration with members at the Weizmann Institute of Science in Israel, the University of Copenhagen, and the University of Augsburg in Germany.
A Microscopic Machine with Ancient Roots
The machine’s function is simple: as electricity courses through the molecule, it rotates, with the direction of its rotation governed by the direction of the voltage applied to the surrounding electrodes.
At the heart of the machine is its unique spiral molecule, an invention that was developed by part of the research team led by Professor Michael Pittelkow, a professor at the University of Copenhagen’s Department of Chemistry, whose Pittelkow Laboratory investigates organic synthesis, physical organic chemistry, chirality, and other related areas.
Pittelkow’s spiral molecule was thereafter positioned between two anatomically sharp gold electrodes by a separate team of researchers at the Weizmann Institute.
Molecular Rotation
Next, as electrons are directed through the spiral molecule, angular momentum is transferred to its structure, which thereby causes it to rotate like wind turning a turbine.
One unique finding the researchers report is that the electrical conductivity of the molecule increased dramatically while rotation was occurring, even by as much as 100 times in certain configurations.
Based on quantum mechanical simulations, it was also revealed during portions of the study led by scientists with the University of Augsburg that rotation appears to allow the molecule to conduct electricity far more efficiently while operating in some of these configurations than when remaining stationary.
“We have shown that an electric current can be used to generate a directed rotation and that this rotation, in turn, controls the current,” said Professor Fabian Pauly, a theoretical physicist and co-author of a recent study detailing the team’s findings.
“This is a new operating principle for machines at the very limits of miniaturization,” he added.
Fundamentally, the team’s achievement could help to advance the fields of molecular electronics, spintronics, and microscopic systems designed for handling fluids—all of which may bring scientists closer to the creation of functional machines that operate at scales as small as a single molecule.
The achievement was reported in a recent study, “Current-Driven Molecular Machine with Rotation-Enhanced Conductance,” which appeared in the journal Nature.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.