“World’s smallest engine” to power microscopic robots

It is often said that size matters. At the nano-scale level, where a lot of current research is being done, this adage also holds true, and several scientific teams have laid claim to creating the “world’s smallest engine” built from particles of ever-shrinking dimensions.

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“has been built from microscopic charged particles of gold that are held together in a gel by using temperature-sensitive polymers, whilst the whole contraption is suspended in water. When heated with a laser, the nano-engine almost immediately takes on and stores a large amount of energy and stores it as mechanical (elastic) energy by forcing the gold nano-particles together into tightly-bonded clusters.

“When the machine is subsequently cooled, the polymer gel absorbs water from its surroundings and rapidly expands, forcefully pushing the gold nano-particles apart with the release of the stored mechanical energy. 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.”