The world's tiniest engine can slip inside living cells

An engineous invention

Nanoengineers at the University of Cambridge have constructed an engine that's just a few billionths of a metre across and could form a solid basis for future nanotechnology.

Nanobots have long been a staple of science fiction, but recent developments in the field have made them look more plausible. It's hoped that they could navigate in liquids, sense the environment around them, and perhaps even enter living cells to deliver medicine to where it's needed.

The engine doesn't remotely resemble what you'd find under the hood of your car. It's made of tiny charged particles of gold, stuck together with a polymer gel that responds to temperature. When it's heated with a laser, it expels all water from the gel and collapses in a fraction of a second, binding the particles together into a tight cluster.

Then, when it cools down again, the the polymer expands and the gold nanoparticles quickly push each other apart. "It's like an explosion," said Tao Ding from Cambridge's Cavendish Laboratory, the first author of a paper describing the discovery. "We have hundreds of gold balls flying apart in a millionth of a second when water molecules inflate the polymers around them."

Like Real Ants

The forces involved are far larger than those for any previously-produced nanoengine, giving the devices way more punch for their weight than any previous motor or muscle. They're also biocompatible, relatively cheap to manufacture, energy efficient and fast to respond.

Jeremy Baumberg, who led the project, refers to them as ANTs, short for Actuating Nano-Transducers. "Like real ants, they produce large forces for their weight," he said. "The challenge we now face is how to control that force for nano-machinery applications."

The team is now working with Cambridge University and several microfluidics companies to commercialise the technology.