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Scientists build a molecular motor and control its movements

10 January 2013

A team of scientists has taken the next step in creating nanoscale machines by designing a multi-component molecular motor that can be moved clockwise and counter clockwise.

Although researchers can rotate or switch individual molecules on and off, the new study is the first to create a stand-alone molecular motor that has multiple parts, said Saw-Wai Hla, an Ohio University professor of physics and astronomy who led the study with Christian Joachim of A*Star in Singapore, and Gwenael Rapenne of CEMES/CNRS in France.

It's an essential step in creating nanoscale devices — quantum machines that operate on different laws of physics than classical machines. Scientists envisage that these could be used for a variety of applications, from powering quantum computers to sweeping away blood clots in arteries.

In the study, published in Nature Nanotechnology, the scientists demonstrated that they could control the motion of the motor with energy generated by electrons from a scanning tunnelling microscope tip. The motor is about two nanometers in length and one nanometer high, and was constructed on a gold crystal surface.

At a temperature of 80K, the motor could move independently through thermal excitation. When scientists cooled the sample to minus 5.4K, the motor stopped rotating. The researchers selectively applied electron energy to different parts of the motor to prompt it to move clockwise and counter clockwise. 

"If we want to build an actual device based on this motor, we would install electrodes on the surface to create an energy source," Hla says. 

To construct the molecular motor, the scientific team designed a stationary base of atoms that is connected to an upper moving part by one atom of ruthenium, which serves as the 'bearing'. The upper piece of the motor features five arms made of iron atoms.

The researchers made one arm shorter than the others to be able to track the motion of the machine. The entire device is held upright by using sulphur as an 'atomic glue' to secure the motor to the gold surface.

The plan is to use this model to build more complex machines with components that could be automated.

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