Recent research progress with synthetic molecular machines continues with a news release from Tufts University reporting “World’s smallest electric motor made from a single molecule“:
Chemists at Tufts University’s School of Arts and Sciences have developed 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 [abstract], the Tufts team reports an electric motor that measures a mere 1 nanometer across, groundbreaking work considering that the current world record is a 200 nanometer motor. A single strand of human hair is about 60,000 nanometers wide.
According to E. Charles H. Sykes, Ph.D., associate professor of chemistry at Tufts and senior author on the paper, the team plans to submit the Tufts-built electric motor to Guinness World Records.
“There has been significant progress in the construction of molecular motors powered by light and by chemical reactions, but this is the first time that electrically-driven molecular motors have been demonstrated, despite a few theoretical proposals,” says Sykes. “We have been able to show that you can provide electricity to a single molecule and get it to do something that is not just random.” …
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.”
The experiment was done at 5 K so that the molecular motion would be slow enough to permit the researchers to track the rotation of the molecule. The molecular motor is a molecule of butyl methyl sulfide adsorbed to a copper surface. The sulfur atom, with a one-carbon arm on one side and a four carbon arm on the opposite side, is the central pivot attached to the copper surface. Addition of electrons from a scanning tunneling microscope tip causes the molecule to rotate, and also supplies images of the molecule while it rotates.
A BBC News article supplies additional comments from Dr Sykes, indicating he is considering more complex molecular machinery as well:
“The next thing to do is to get the thing to do work that we can measure – to couple it to other molecules, lining them up next to one another so they’re like miniature cog-wheels, and then watch the rotation propagation down the chain,” he said.