World's smallest engine created

Scientists from the Cavendish Laboratory in Cambridge have created the world’s tiniest engine – a few billionths of a metre – powered by light.

It is thought these engines could power future nano-machines, enabling them to navigate in water, enter cells to fight disease and have the ability to sense their surrounding environment.

The engine, made of tiny charged particles of gold bound with a temperature responsive polymer gel, stores large amounts of energy when heated with a laser. This expels water from the polymers forcing the gold nanoparticles to bind together tightly. As the device cools, it absorbs water and the nanoparticles are strongly and quickly pushed apart.

Dr Tao Ding, first author and a scientist at the Cavendish Laboratory, said: “It's like an explosion. We have hundreds of gold balls flying apart in a millionth of a second when water molecules inflate the polymers around them.”

The forces exerted by these actuating nano-transducers (ANTs) are several orders of magnitude larger than any previously created device. Their force per unit weight is almost one hundred times better than any motor or muscle, said the researchers.

Professor Jeremy Baumberg from the Cavendish Laboratory, said: “Like real ants, they produce large forces for their weight. The challenge we now face is how to control that force for nano-machinery applications.”

Describing the process as similar to a nano-spring he said: “The smart part here is we make use of Van de Waals attraction of heavy metal particles to set the springs (polymers) and water molecules to release them, which is very reversible and reproducible."

The researchers are working with the university’s commercialisation arm, Cambridge Enterprise and other companies with a view of commercialisation for microfluidics bio-applications.

The study was published in PNAS.