Water found to be an ideal lubricant for nanomachines

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Posted on September 2, 2013
Molecular motor

Molecular motor
A molecular motor lubricated by water. This molecule consists of a ring that can move over a wire. If the molecule absorbs light the ring moves from one end of the wire to the other. When this happens light energy is converted into kinetic energy (similar to a piston in a petrol engine). By adding a small amount of water to the solution around the motor, the ring moves twice as quickly. Credit: FOM

Researchers from the University of Amsterdam have discovered that machines just one molecule in size move far quicker if you add a ‘lubricant’ to their surroundings. To their surprise, water proved to be the best lubricant by far. The research will be published on 1 September 2013 in Nature Chemistry.

FOM PhD researcher Matthijs Panman and his colleagues determined the velocity of two nanomachines: minuscule machines just one single molecule in size. They examined a molecular wheel and a molecular motor driven by light. Both machines are made up of just a few dozen atoms and are about one thousandth millionth of a metre in size.

Lubricated motion

The researchers used advanced physics techniques (nuclear spin resonance and ultrafast lasers) to examine the molecular machines. During the research the machines were dissolved in an organic solvent (acetonitrile). The researchers discovered that if a small quantity of water was added to the solvent, the molecular machines moved much faster. Three percent water proved to be enough ‘lubricant’ to make the movement more than twice as quick.

The researchers added other substances as well but the less similar to water the substance added was, the less good its lubricating effect. Butanol, which in terms of properties is in between water and lubricating oil actually made the movement slower.

Broken bonds

It is not yet entirely clear why water is such a good lubricant for the nanomachines investigated. The lubricating effect is probably associated with the hydrogen bonds (weak bonds) between the groups of atoms that form the two parts of these machines that move with respect to each other.

Read more at: Phys.org