Chemists at Tufts University's School of Arts and Sciences have built the world's first single molecule electric motor, a development that may potentially create a new class of devices that could be used in applications ranging from medicine to engineering.
In research published online September 4 in Nature Nanotechnology, the Tufts team reports an electric motor that measures 1 nanometer across.
E. Charles H. Sykes, Ph.D., associate professor of chemistry at Tufts and senior author on the paper, and his colleagues were able to control a molecular motor with electricity by using a low-temperature scanning tunneling microscope (LT-STM). The LT-STM 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 that had been 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.
By controlling the temperature of the molecule, the team could directly impact the rotation of the molecule. Temperatures around 5 Kelvin (K), or about minus 450 degrees Fahrenheit (ºF), 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.
While there are foreseeable practical applications with this electric motor, breakthroughs would need to be made in the temperatures at which electric molecular motors operate. The motor 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."
