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'World's smallest electric motor' consists of a single molecule


September 5, 2011

The molecular motor (yellow dot with black arms) sits on a copper surface (orange) and is powered by electrons from the tip of a scanning tunneling microscope (gray)

The molecular motor (yellow dot with black arms) sits on a copper surface (orange) and is powered by electrons from the tip of a scanning tunneling microscope (gray)

Remember back in the old days, when nano-scale motors were a clunky 500 nanometers across? That record was subsequently broken with a 200-nanometer model, but has now been broken again, by a motor that's just one nanometer wide. By comparison, the width of a human hair is about 60,000 nanometers. The new motor, created by scientists at Tufts University in Massachusetts, is reportedly the first one ever to consist of a single molecule.

More specifically, the motor consists of a butyl methyl sulfide molecule that is located on a conductive copper surface. Arm-like structures made up of carbon and hydrogen atoms protrude from either side of the molecule, with one containing four carbon atoms, and the other containing one. While the sulfur in the molecule causes it to bond with the copper surface, the two arms are free to rotate around its base.

By providing electricity from the metal tip of a low-temperature scanning tunneling microscope, the team was able to cause the molecule to rotate. Altering the temperature of the molecule was shown to affect the speed of its rotation, with a temperature of 5 Kelvin (-268C/-450F) turning out to be ideal for tracking its motion. While higher temperatures caused it to spin significantly faster, it proved difficult to track and control its rotation at such speeds.

"Once we have a better grasp on the temperatures necessary to make these motors function, there could be real-world application in some sensing and medical devices which involve tiny pipes," said associate professor of chemistry, E. Charles H. Sykes. "Friction of the fluid against the pipe walls increases at these small scales, and covering the wall with motors could help drive fluids along. Coupling molecular motion with electrical signals could also create miniature gears in nanoscale electrical circuits; these gears could be used in miniature delay lines, which are used in devices like cell phones."

The Tufts team plans on submitting the motor to Guinness World Records. A report on the research was recently published in the journal Nature Nanotechnology.

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away. All articles by Ben Coxworth

a molecular sized electric motor.. Ok that is impressive...

Michael Mantion

What a joke. This may be the smallest rotor, but it is a huge motor. To get it to turn in one direction it needs a commutating switch, not a human pressing a button to get it to spin in a particular direction \"mostly\". It also needs a stator to be a motor...that happens to be a full blown tunneling microscope - hardly even microscopic. Guinness is insane if they admit this as a motor, which it isn\'t. If it is, then my motor is smaller...I apply a mag field to an Fe atom and spin its electron....put me in the record book.


The old 500 nm and 200 nm motors are staying inside, trying to avoid taunting questions from the press: \"How does it feel to be kind of a, I don\'t want to say a has-been, but...\" and \"Are you watching your weight?\"

Now what will make these single-molecule motors look pitiably obsolete? Maybe femto-bots, the size of a few protons, designed for stirring groups of electrons inside an atom. They make sugar taste sweeter!

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