A team of researchers at the University of Cambridge, UK, has developed a nanoscale engine — just a few billionths of a meter in size — which uses light to power itself.
Reversible assembly of light-powered nano-engines. pNIPAM – poly(N-isopropylacrylamide). Image credit: Tao Ding et al / University of Cambridge.
The prototype nano-engine is made of small charged particles of gold (Au), bound together with temperature-responsive polymers in the form of a gel.
When the engine is heated to a critical temperature (89.6 degrees Fahrenheit, or 32 degrees Celsius) 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 triggers a controllable number of gold nanoparticles to tightly bind in 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. We have hundreds of gold balls flying apart in a millionth of a second when water molecules inflate the polymers around them,” said team member Dr. Tao Ding, lead author on a paper published this week in the Proceedings of the National Academy of Sciences.
“We know that light can heat up water to power steam engines,” added co-author Dr. Ventsislav Valev.
But now we can use light to power a piston engine at the nanoscale.”
According to the team, their nano-engines are also bio-compatible, cost-effective to manufacture, fast to respond, and energy efficient.
“Like real ants, they produce large forces for their weight,” said senior author Prof. Jeremy Baumberg.
“The challenge we now face is how to control that force for nano-machinery applications.”
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Tao Ding et al. Light-induced actuating nanotransducers. PNAS, published online May 2, 2016; doi: 10.1073/pnas.1524209113
