An international team of scientists has created a molecular motor inspired by the ancient Archimedes screw. The device, only a few nanometres in size, can rotate under the action of an electric current and reverse direction when the voltage polarity is switched.
At its core is a helical helicene molecule, synthesised by the team of Professor Michael Pittelkow at the University of Copenhagen. It was anchored between two gold electrodes with atomic precision at the Weizmann Institute of Science in Israel.
When a voltage is applied, electrons passing through the helix transfer angular momentum to it — just as a flow of water turns a screw. The direction of rotation is set by the molecule's "thread" and is fully controlled by the polarity of the current.
This is the first demonstration of a molecular motor driven by an electric current, rigidly fixed between two metal electrodes and capable of rotating in a controlled direction.
Researchers from the University of Augsburg carried out quantum-mechanical simulations. They showed that upon reaching a certain rotation speed, the molecule's conductance rises sharply — by up to 100 times.
The experiments were conducted under the leadership of Professor Oren Tal and Dr Anil Kumar Singh. The theoretical part was led by Professor Fabian Pauly.
The work has been published in the journal Nature. How will it affect the development of molecular electronics in the coming years?
The device opens up a new principle of operation for nanomachines: current sets off rotation, and rotation, in turn, amplifies the current. The scientists note that the amplification threshold can be tuned by stretching or compressing the molecule.
