A machine inspired by an ancient water pump can now operate at the scale of a single molecule. 

A team of international researchers has built a tiny motor that uses an electric current to drive a screw-shaped molecule into rotation, while the movement itself can increase the current flowing through it by up to 100 times. 

This discovery establishes a new way to couple mechanical motion and electricity at the smallest scales, opening new possibilities for molecular electronics.

Scientists have spent decades trying to build artificial molecular machines inspired by the motors that power movement inside living cells. However, making a molecule rotate predictably under an electric current while maintaining electrical contact with metal electrodes has remained a challenge. 

The new device demonstrates voltage-controlled rotation with 100 percent directional preference, using a principle that dates back more than 2,000 years. 

“We have shown that an electric current can be used to generate a directed rotation and that this rotation, in turn, controls the current. This is a new operating principle for machines at the very limits of miniaturization,” Fabian Pauly, one of the study authors and a professor at the University of Augsburg in Germany, said.

The researchers took inspiration from the Archimedes’ screw, an ancient device with a helical blade inside a cylinder that lifts water (or solids) when rotated. In the new machine, electrons flowing through a similarly twisted structure generate the torque that makes it rotate. 

Instead of relying on an external mechanical tool to move the molecule, the current itself powers the motion.

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