Molecular Machines...

The use of pulses of chemical fuel to directionally transport components and substrates via an energy ratchet mechanism is operationally simple, effective, generates relatively innocuous waste products, and can function in a range of rotary and linear molecular motor and pump designs. Such a universally applicable chemically-fuelled molecular motor-mechanism has the potential to find broad application in molecular nanotechnology. Courtesy: D Leigh

Topics: Brownian Motion, Chemistry, Nanotechnology, NEMS

Chemists at the University of Manchester in the UK say they have succeeded in developing a new and simple technique for powering both linear and rotary molecular motors made from catenanes. These are mechanically interlocked rings of DNA that could be used to make devices that can be switched between different states using external triggers like changes in pH. The breakthrough method – until now it was only possible to power either rotary or linear motors – might be used to power future molecular machines.

“In the molecular machines we are familiar with in the ‘big world’, the parts, such as cogs, flywheels and pistons, do not move unless a force is applied to them,” explains team leader David Leigh. “At the molecular scale, however, molecules and their parts are constantly moving through Brownian motion and we need to find ways to control the direction of this motion if we are to develop fully-functioning nanomachines.”

Last year, Leigh’s team made the first autonomous chemically-fuelled molecular motor that runs as long as a chemical fuel is present. This rotary motor relies on information transfer between the machine components: a blocking group adds as soon as the ring has moved past a certain point in a given direction and that group also prevents the ring moving backwards through Brownian motion.

The researchers use trichloroacetic acid (Cl₃CCOOH) as the fuel in their motor. Cl₃CCOOH undergoes base-catalysed decarboxylation, and by adding an excess of this acid to a solution containing the molecular motor and another chemical (triethylamine, or Et3N), they were first able to make the medium acidic and then, as the Cl₃CCOOH decomposes, basic.

Chemical fuel pulses power rotary and linear nanomotors, Belle Dumé, Nanotechweb.org