Scientists create single molecule motor

Scientists at Tufts University in the US have created the world’s smallest multi-directional motor, measuring just one-billionth of a metre across. The tiny device – a single molecule of butyl methyl sulphide – operates at up to 120 revolutions per second. It is the first of its kind that can be controlled individually by electric current.

When placed on a copper surface, the single atom of sulphur acts as a pivot. A Scanning Tunnelling microscope directs electrons towards the rotor to power the movement. Changing the temperature, the speed and the amount of electrons in the current impacts on the rotor meaning that its movement can be measured in real time.

Similar experiments with this level of nanotechnology have taken place elsewhere and ‘molecular motors’ powered by light and chemical reaction have also been developed in the past. The difference with this electrically powered motor is the potential for a level of control that allows for focused work such as delivering drugs directly to the smallest areas of the body.

Progress in the use of molecular machinery requires the coupling of individual molecules to external energy sources that can then be selectively moved, and the team at Tufts has achieved this. They are currently contacting the Guinness Book of World Records to formally register their success in building the smallest motor ever.

Glossary

Scanning Tunnelling Microscope (STM)

An instrument for imaging surfaces at the atomic level. The conducting tip of the microscope carries a bias, or voltage difference, between it and the surface to be examined. When close to the examined surface the bias allows quantum tunnelling through the vacuum of electrons. More recently it has been used to rotate individual bonds within single molecules, and with this rotation the molecule effectively becomes a switch.