One of the great discoveries of biology is that the engines of life are molecular motors–tiny machines that create, transport and assemble all living things. 

That’s triggered more than a little green-eyed jealousy from  physicists and engineers who would like to have molecular machines at their own beck and call. So there’s no small interest in developing molecular devices that can be easily harnessed to do the job.

Today, Jin Zhang at the University of California Los Angeles and a few pals say they’ve identified a machine that fits the bill.

A couple of year ago, chemists discovered that groups of 13 or 19 boron molecules form into concentric rings that can rotate independently, rather like the piston in a rotary Wankel engine. Because of this, they quickly picked up the moniker “molecular Wankel engines”. The only question was how to power them. 

Now Zhang and buddies have calculated that this should be remarkably easy–just zap them with circularly polarised infrared light. That sets the inner ring counter-rotating relative the outer one, like a Wankel engine.

Of course, nanotechnologists have identified many molecular motors and even a few rotary versions (ATP springs to mind). 

What makes this one special is that the polarised light doesn’t excite the molecule’s electronic ground state,  leaving it free to be chemically active.

By contrast, other forms of molecular power such as chemical or electric current can generate heat that has a critical effect on the system.

For the moment, the photon-powered molecular Wankel engine is merely an idea, the result of some detailed chemical modelling.

Zhang and co leave it to others, who are  happy to get their hands dirty, to actually get one of these molecules turning. 

If they’ve got their sums right, that should be sooner rather than later.

Ref: arxiv.org/abs/1204.2505: Photo-driven Molecular Wankel Engine, B13+