The world’s tiniest engine could power tomorrow’s nanomachines

Yi Ju/University of Cambridge NanoPhotonics

Original press release was issued by the University of Cambridge.

Nanomachines have long been the dream of many scientists and science-fiction fans alike. However, with the latest research into nano-scale engines from the University Cambridge, we may finally be on the cusp of real life, fully functional nano-bots that appear to be extraordinarily efficient and scalable.

What researchers have developed is essentially the world’s tiniest engine that is just a billionth of a metre small, and uses light to power itself. The technology used would allow it to power nanomachines capable of navigating in the water, sense the environment around them, or enter living cells to fight disease.

“We know that light can heat up water to power steam engines,” said study co-author Dr Ventsislav Valev. “But now we can use light to power a piston engine at the nanoscale.”

The prototype device is made of tiny charged particles of gold, bound together with temperature-responsive polymers in the form of a gel. When the ‘nano-engine’ is heated to a certain temperature with a laser, it stores large amounts of elastic energy in a fraction of a second, as the polymer coatings expel all the water from the gel and collapse. This has the effect of forcing the gold nanoparticles to bind together into tight clusters. But when the device is cooled, the polymers take on water and expand, and the gold nanoparticles are strongly and quickly pushed apart, like a spring.

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

The prototype isn’t just functional – it is efficient. Its ratio of force per unit weight exceeds those of all previously produced devices, including ordinary engines and muscles. On top of that, it is reported to be bio-compatible, cost-effective to manufacture, fast to respond, and energy efficient.

Professor Jeremy Baumberg from the Cavendish Laboratory, who led the research, has named the devices ‘ANTs’, or actuating nano-transducers. “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.”

The research suggests how to turn Van de Waals energy – the attraction between atoms and molecules – into elastic energy of polymers and release it very quickly. “The whole process is like a nano-spring,” said Baumberg. “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 team is currently working with Cambridge Enterprise, the University’s commercialisation arm, and several other companies with the aim of commercialising this technology for microfluidics bio-applications.

Michal Dudic

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