The world’s smallest engine uses light to power itself

Researchers from the University of Cambridge have developed a nano-engine that could be used in the field of nano-robotics to create robots small enough to enter living cells.

The engine, just a few billionths of a meter in size, which uses light to power itself and could form the basis of future nano-machines that can navigate in water, sense their surroundings, or even enter living cells to fight disease.

Expanding polymer-coated gold nanoparticles. (Image Credit: Yi Ju/University of Cambridge)
Expanding polymer-coated gold nanoparticles. (Image Credit: Yi Ju/University of Cambridge)

The prototype is made of tiny charged particles of gold that are bound with a gel composed of temperature-responsive polymers. When the nano-engine is heated with a laser, it stores large amounts of elastic energy in just fractions of a second as the polymer coatings expel all the water from the gel and collapse. This process forces the gold nanoparticles to bind together into tight clusters. When the device is cooled, though, the polymers take in water and expand, causing the gold nanoparticles to be 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.”

Scientists have been working toward developing nano-machines for a while, but have yet to figure out a way to actually make them move. The new method developed by the researchers is simple, but can be extremely fast and exert large forces.

The tiny devices, nicknamed “ANTs”, or actuating nano-transducers, can exert force several orders of magnitude larger than those used in any other previously produced device, with a force per unit weight nearly a hundred times better than any motor or muscle. They are also bio-compatible, cost-effective, quick to respond, and energy efficient.

The team likens the engines to real ants that can produce large forces for their weight.

Now, the researchers will have to figure out how to control that force for use in nano-machinery applications.

They are currently working with Cambridge Enterprise, the University’s commercialization arm, and several other companies with the goal of bringing this technology to market for microfluidics bio-applications.

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