Scientists develop nano-sized electric motor

Scientists 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.

The electrical motor measures just one nanometre. About 60,000 of them equal the width of a human hair.

The molecular motor is a breakthrough that could lead to new types of electrical circuitry, according to Charles Sykes, an associate professor of chemistry at Tufts University in Massachusetts.

In a research published online on September 4 in Nature Nanotechnology, the Tufts team has reported an electric motor that measures a mere 1 nanometre across, a groundbreaking work considering that the current world record is a 200 nanometre motor.

According to Sykes, 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," 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," he said.

Sykes and his colleagues were able to control a molecular motor with electricity by using a state of the art, low-temperature scanning tunnelling 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 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.

The team determined that by controlling the temperature of the molecule they could directly impact the rotation of the molecule.

Temperatures around 5 Kelvin (K), or 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 analyse 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," said Sykes.

"Coupling molecular motion with electrical signals could also create miniature gears in nanoscale electrical circuits which could be used in devices like cell phones," he said.

To work in the real world the researchers will need to get it operate at more practical temperatures. Getting there, he said, is likely several decades out, but doable.