World’s smallest electric motor made from a single molecule

September 6, 2011

Single-molecule electric motor (credit: Heather L. Tierney et al./Nature Nanotechnology)

Chemists at Tufts University‘s School of Arts and Sciences have developed the world’s first single-molecule electric motor, which may create a new class of devices used in medicine and engineering.

It measures a mere 1 nanometer across (the current world record is a 200 nanometer motor).

According to E. Charles H. Sykes, Ph.D., associate professor of chemistry at Tufts, the team plans to submit the Tufts-built electric motor to Guinness World Records.

They used a state of the art, low-temperature scanning tunneling microscope (LT-STM), which uses electrons instead of light to “see” molecules.

The team used the metal tip on the microscope to provide an electrical charge to a butyl methyl sulfide molecule placed on a conductive copper surface. This sulfur-containing molecule had carbon and hydrogen atoms radiating off to form what looked like two arms, with four carbons on one side and one on the other. These carbon chains were free to rotate around the sulfur-copper bond.

The team determined that by controlling the temperature of the molecule, they could directly impact the rotation of the molecule. Temperatures around 5 degrees Kelvin (about minus 450 degrees Fahrenheit) proved to be the ideal to track the motor’s motion. At this temperature, the Tufts researchers were able to track all of the rotations of the motor and analyze the data. It spins much faster at higher temperatures, making it difficult to measure and control the rotation of the motor.

“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. Friction of the fluid against the pipe walls increases at these small scales, and covering the wall with motors could help drive fluids along,” said Sykes. “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.”

Ref.: Heather L. Tierney, et al., Experimental demonstration of a single-molecule electric motor, Nature Nanotechnology, 2011; [DOI:10.1038/nnano.2011.142]