Chemists at Tufts University's School of Arts and Sciences have developed the world's first single molecule electric motor—a development that may create a new class of devices applicable to sectors like medicine to engineering.
In a report published in Nature Nanotechnology this month, the Tufts team reported an electric motor only one nanometer across—groundbreaking work, considering the current world record is a 200-nanometer motor. A single strand of human hair is about 60,000 nanometers wide.
E Charles H Sykes, associate professor of chemistry at Tufts and senior author of the paper, says, “There has been significant progress in the construction of molecular motors powered by light, and by chemical reactions. But this is the first time electrically-driven molecular motors have been demonstrated, despite a few theoretical proposals…We have been able to show one can provide electricity to a single molecule and get it to do something that is not just random.”
Sykes and his colleagues were able to control a molecular motor with electricity by using a state-of-the-art, low-temperature scanning tunneling microscope (LT-STM), one of about only 100 in the United States. 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 placed on a conductive copper surface. This sulfur-containing molecule had carbon and hydrogen atoms radiating 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.
While there are foreseeable practical applications of 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.