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Just invented recently, these steam engines are smaller than red blood cells and most bacteria between one and three millionths of a meter. The significantly strong pistons are powered by a combined process of optical manipulation which bypasses microfabrication and draws strength from simplicity.
To our eyes, they look just like little pulsing circles (almost like what we’re accustomed to interpreting as biology under a microscope). But they are tiny explosions in water.
What is happening to create this explosion is due to the combination of two techniques.
Optical tweezers focus laser beams on a spot. The beam causes microscopic objects to move toward the point where it hits the water. But when the objects get there, they would like to stay there, but instead, there are microscopic vapor explosions that drive everything out (replacing it all with a bubble). The explosion forces things out with a force several times that of the force of the optical tweezers.
It’s this combination — the two forces working one after the other — that is the mechanics of the piston.
“The piston is a microsphere is powered by light, which also heats the sphere inducing the vapor microexplosions. Similar to an internal piston combustion engine,” said Dr. Pedro Quinto-Su of his inventions. “This is the first time that a steam engine has been miniaturized to a length scale of a micrometer.”
“The combination of optical tweezers and vapor explosions resulted in a microparticle (piston) that is periodically attracted towards the focused laser and then is pushed away at a fast speed by microscopic vapor explosions. In a sense it is similar to an internal piston combustion engine.”
This is the tiniest piston ever. It produces significant power though… for its size: 0.3 pico Watts on average.
The challenge of the past with regards to making a tinier piston was that they were based on the heat engine model, which is limited in efficiency. Even still, they were demonstrated at micrometer size.
But these pistons are only as big as a red blood cell, or as big as a single bacterium.
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