Tiny Engines

Researchers from the University of Cambridge have just devised a tiny engine—a really tiny engine—that will likely play a key role in realizing the long-awaited dream of truly functional nanotechnology.

Such technology has long been in the offing, and has been much touted for its enormous potential—imagine tiny machines or cellular analogues roaming the bloodstream (à la Fantastic Voyage) and zapping cancerous cells, coming to grips with foreign bacteria and viruses, correcting prion diseases, and rejiggering the genomes of patients suffering from genetic disorders.

Imagine, too, what effects such technology could have on materials science, computing, optics…well, the possibilities are virtually endless, so you can pretty well guess that it has the capacity to change the world.

But scientists have had to start with baby steps, because manipulating matter on the nanoscale is notoriously difficult. One major hurdle has been how to supply power to such fantastically minute devices—and the newly discovered engine may be the solution to this problem.

The Gold-Seekers

The prototype engine does not resemble a classic one: It consists of a jumble of charged gold nanoparticles, clustered together in a “smart” gel of temperature-sensitive polymers. The actual power principle behind the engine is quite simple—no more complicated than the principles powering a slingshot. When the polymerous bundle is heated by a laser, the polymer gel expels water from the mass, which collapses, storing significant quantities of elastic energy.

When the bundle shrinks, the gold nanoparticles are bunched together very tightly, but once the polymers cool, they suck up the expelled water and rapidly expand, causing the gold particles to quickly spring apart and releasing the elastic energy.

And there you have it: A simple, but very effective, nanoscale engine. It’s an ingenious use of fundamental forces operating at this tiny scale, and its practical application would probably involve something like a light-powered piston engine.

Lead researcher professor Jeremy Baumberg, of the Cavendish Laboratory, says, “The whole process is like a nano-spring. The smart part here is we make use of Van der Waals attraction of heavy metal particles to set the springs (polymers) and water molecules to release them, which is very reversible and reproducible.”

These littlest motors also produce forces several orders of magnitude greater than previous devices, besting the force per unit weight of other motors and muscles by nearly a hundredfold. The team has christened the devices “ANTs”— “actuating nano-transducers,” which is very apt, considering that tiny insect’s notorious propensity to do heavy lifting all out of proportion to its size.

The team asserts that the little machines will be cheap to manufacture, are very energy efficient, and could be inserted in biological systems with no threat. The next phase is to collaborate with several companies to commercialize the technology.