Scientists Build Smallest, Single Atom, Working Heat Engine (popularmechanics.com)

William Herkewitz, writing for Popular Mechanics: Physicists have just built the smallest working engine ever created. It's a heat-powered motor barely larger than the single atom it runs on. Designed and build by a team of experimental physicists led by Johannes at the University of Mainz in Germany, the single atom engine is about as efficient as your car at transforming the changing temperature into mechanical energy. While scientists have previously created several micro-engines consisting of a mere 10,000 particles, Johannes's new engine blows these out of the water by paring down the machine to a singular atom housed in a nano-sized cone of electromagnetic radiation. The project is outlined today in the journal Science. "The engine has the same working principles as the well-known [combustion] car engine," Johannes says. It follows the same four strokes; expanding then cooling, contracting then heating.There's some confusion here. The article says it's a "four-stroke" engine. But as we know, a four-stroke engine consists of an intake stroke, a compression stroke, a power stroke, and an exhaust stroke -- things that the engine in the article doesn't seem to have. The article doesn't mention how a single atom is able to mimic all the effects of a combustion engine. Update: 04/15 18:24 GMT by M :The article appears to have been updated for clarification.

Comments

Smallest?

[Anonymous Coward]

I think the part that creates nano-sized cone of electromagnetic radiation counts as part of the engine.

Re:Smallest?

[Thelasko]

I think the part that creates nano-sized cone of electromagnetic radiation counts as part of the engine.

I question it being called a heat engine at all. The energy source is a laser. A laser is a highly organized beam of radiation. Heat is disorganized. This seems to have more in common with a photoelectric effect. The big difference from the photoelectric effect being the fact this system creates mechanical work instead of electric current.

Re:Smallest?

[somenickname]

My initial thought as well. Reading the article, what they've actually created is a single atom piston with insanely complex machinery to drive the piston. Still pretty cool but, pretty far from a "single atom working heat engine".

Re:Smallest?

[Thelasko]

what they've actually created is a single atom piston with insanely complex machinery to drive the piston.

Great analogy! When you factor in all of the equipment involved, this "engine" has perhaps the worst power density in the world.

Re:Smallest?

[MattskEE]

The researcher acknowledges this, as quoted in the article:

Roßnagel openly admits that you won't find his four-stroke motor in any nano-sized robots anytime soon. While the engine itself is tiny, the machinery required to create the electromagnetic cone and suspend the two heating and cooling lasers takes up most of a room. But Roßnagel says that's no surprise. The engine was never meant to be a functioning part of a future machine, but to reveal new insights into the fundamental science of heat engines. Until now it wasn't clear that such a tiny engine would even work.

"I don't see a direct application for this engine. We do fundamental research and try to get a better understanding of thermodynamics of single particles," he says. Still, "this improved understanding can (and will, I'm convinced) lead to a next generation of experiments and to future devices which will be interesting for various applications," Roßnagel says. Maybe future robotic parts or single-atom refrigerators?

"[We now know] it is possible to realize a heat engine with a single atom," he says, "while maintaining the same working principles as for macroscopic engines."

Popular Mechanics

[110010001000]

It is a Popular Mechanics article, of course there is some confusion. Sensationalism is that they sell nowadays. It used to be a good magazine.

Re:Popular Mechanics

[Anonymous Coward]

The authors of this paper are referring to the four thermodynamic states of an engine. The "4-stroke" of a combustion engine refers to the mechanical devices used to transition the system from one state to another. They are conceptually related, hence the analogy.

otto cycle

[Anonymous Coward]

It follows the same four strokes; expanding then cooling, contracting then heating.

These are the four strokes of the Otto Cycle.

There's some confusion here. The article says it's a "four-stroke" engine. But as we know, a four-stroke engine consists of an intake stroke, a compression stroke, a power stroke, and an exhaust stroke -- things that the engine in the article doesn't seem to have.

Intake-compression-power-exhaust are how a reciprocating piston achieves expand-cool-contract-heat.

Imma go stage 2

[danbert8]

I wonder if you could put a turbo in the exhaust and use it to cram 2 atoms in the engine to get some more power out of it...

The Physics

[Thelasko]

My understanding of heat is it's the kinetic energy of molecules. What makes an engine is the ability to get all of the molecules to exert their energy in the same direction to do work. I like to think of the fish in the net from Finding Nemo.

If you only have a single molecule, that basically means you have a heat engine. There must be some different definition of heat than I use. Perhaps they are demonstrating radiation heating?

Re:The Physics

[DRJlaw]

That was not my impression. There's a bulk, "mechanical" process where the temperature stays constant because water is boiled into steam which leaves the system. But there's also an underlying, physiochemical phase transition where you could (theoretically) add energy just short of the enthalpy of vaporization without generating any additional steam (remember, the saturated gas phase issue). You can't actually do that due to statistical thermodynamics, but the enthalpy of vaporization is a form of physical bond breaking, not merely energy being lost due to the generation of steam.

Somehow the name got mangled

[Sique]

Probably because the german spelling of the name of the lead scientist contains the "sz" letter, his family name apparently got omitted from the submussion. His full name is Johannes Rossnagel. (If you don't have the ß, use ss instead!).