A team of researchers from the University of Cambridge created the world's tiniest engine, measuring just a few billionths of a meter in size. The nanoscale engine uses light to power itself and could provide the framework for future nano-machines used for numerous purposes, including entering living cells to fight disease and navigating water.
The device is made from tiny charged gold particles, each bound together using temperature-responsive polymer gels. Using a laser, the engine's temperature is increased and, when it reaches a certain level of heat, it stores large amounts of elastic energy as the polymer coating releases the water from the gel and falls apart. This process pushes the gold nanoparticles together into tight clusters. However, when the engine is cooled, the polymer gels absorb water and expand, pushing the nanoparticles apart.
"It's like an explosion," said Tao Ding from the University of Cambridge and first author of the study. "We have hundreds of gold balls flying apart in a millionth of a second when water molecules inflate the polymers around them."
"We know that light can heat up water to power steam engines," added Ventsislav Valev, a co-author of the study who is currently at the University of Bath. "But now we can use light to power a piston engine at the nanoscale."
Although nano-machines have long been a dream of scientists, making them move is the problem. The new method described in the current study could potentially solve this problem and, despite its simplicity, it can be extremely fast and exert large forces.
In comparison to other previously produced devices, the new engine creates forces several orders of magnitude bigger, creating a force per unit weight that is almost one hundred times that created by any motor or muscles. Furthermore, the engines are cost-effective, bio-compatible and energy efficient.
"Like real ants, they produce large forces for their weight," said Jeremy Baumberg from the Cavendish Laboratory, who led the study and has named the devices "ANTs." "The challenge we now face is how to control that force for nano-machinery applications."
The team is currently working to commercialize the new nanoscale engine technology for use in microfluidics bio-applications.
The findings were published in the May 2 issue of the Proceedings of the National Academy of Sciences.
