Abhilasha Bora
Sep 7, 2011

Single molecule powers electric motor: Nanotechnology shrinks the world

Researchers at Tufts University in Somerville, Massachusetts, have taken a proud next step in nanotechnology by creating the world's smallest electric motor, the size of a single molecule and made from a molecule too.

The motor is a single molecule that accepts an electrical charge and rotates as fast as 120 revolutions per second. It measures a billionth of a meter, or just one nanometer across. To put that into perspective, a human hair is 60,000 nanometers in diameter.

The team, led by Associate Professor of Chemistry Charles Sykes, managed to rotate a single butyl methyl sulfide molecule—basically, a sulfur molecule with two "arms" made of carbon and hydrogen atoms—back and forth, using a technology that only now appears simple. When laid on a copper surface and stimulated with electricity, the molecule began to rotate, swinging its arms round and round, just a like a macroscopic motor. A scanning tunneling microscope (of which there are only 100 in the US) zapped the molecule with an electric current from a tip measuring just one or two molecules across, making it spin.

A caveat to this breakthrough, however, is that it was possible to do this only at a very low temperature of 5 degrees Kelvin, or minus 450 degrees F, slowing the molecules down to the point where the number of rotations per second was about 50. The motor still rotated at higher temperatures, but the number of rotations was off the scale. At minus 279 degrees Fahrenheit, for example, the number of rotations was more than a million every second. 

Source: http://gasstationwithoutpumps.files.wordpress.com/2011/09/dn20863-1_300.jpg?w=300&h=364

Motors this small have been demonstrated before, but they've been powered by heat, chemicals or light. This is the first molecular motor to run on electricity.

Sykes stated that 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. "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 stated.

An electric motor this small could well be used to power nanotechnology-based devices. A device that small could be used in surgery by introducing it into a person's body to perform procedures on individual cells. In engineering, tiny motors could power nano-scale machines like sensors.

However, before the technology can be applied fully at common temperatures rather than freezing temperatures meant only for experimental purposes, the team may need a few more years. They could also explore creating whole new molecules and surfaces where the technology could be utilized more efficiently. We cannot say if patents could follow this, especially after so much that has been written about it already, unless there are patent applications already pending before the patent offices. For now, the team can celebrate having secured themselves an entry in the "Guinness Book of World Records" for the world’s smallest electric motor.