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Heat Engines Shrunk By Seven Orders of Magnitude
KentuckyFC writes "The vast majority of motors that power our planes, trains, and automobiles are heat engines. They rely on the rapid expansion of gas as it heats up to generate movement. But attempts to shrink them by any significant amount have mostly ended in failure. Today, the smallest heat engines have a volume of some 10^7 cubic micrometers. Now group of Dutch engineers has built a heat engine that is seven orders of magnitude smaller than this. The engine consists of a piezoelectric bar that expands and contracts in the normal piezoelectric way. However it also heats up and cools at the same time causing a thermal expansion and contraction, which lags the piezoelectric displacement. By carefully choosing the frequency of the driving AC current, the Dutch team found a resonant effect in which the thermal expansion and contraction amplifies the mechanical motion, making it a true heat engine. Operating the thermodynamic cycle in reverse turns the device into a heat pump or refrigerator. The total volume of the device is just 0.5 cubic micrometres."
You know how big a millimeter is, right? A micrometer is one thousandth the length of a millimeter.
A cubic micrometer is the volume occupied by a cube one micrometer on each side.
10^7 cubic micrometers would fill a cube about one-fifth of a millimeter on a side. Smaller than a pinhead.
"Trolls they were, but filled with the evil will of their master: a fell race..." -- J.R.R. Tolkien on Olog-hai
Fun fact - Wolfram Alpha can serve as your 'self-checkout line' for things like this.
http://www.wolframalpha.com/input/?i=1+cubic+micrometer
Here's a bit of scale - a cubic micrometer is about the same size as a calibration bead for microscopy. A red blood cell is about 8 micrometers across. http://learn.genetics.utah.edu/content/begin/cells/scale/ Or, there's this video showing the "powers of ten" (also its title...): http://www.youtube.com/watch?v=A2cmlhfdxuY
Also, chemists work at these dimensions, too! (So do biologists. And others.) :*P Don't snub the other disciplines!!! Or I'll weep. And not gently, nor to a guitar.
Be careful of your thoughts; they could become words at any minute...
Somehow "heat engine" directly translates into "internal combustion engine" for me.
That's too bad, I hope this article will be enough to let you correct your thought
why emphasize that it is a heat engine?
Because they figure it's mostly usefull as a heat pump, not as a mechanical actuator.
You can't take the sky from me...
about one-fifth of a millimeter on a side
That's about the thickness of a sheet of paper. (Round here, and probably in a lot of the world, the thickness and density of paper is specified, for instance "160 g/m^2, 200 micrometres".)
The internal combustion engine is only one class of heat engines. The Sterling Engine and the External Combustion Engine (used in old steam locomotives) are also heat engines. Heat engines use heat to create power either by taking advantage of temperature differences or the expansion of heated air.
Somehow "heat engine" directly translates into "internal combustion engine" for me.
A steam engine is an external combustion engine, yet is is still a heat engine. The thing with this teensy engine is that it reuses waste heat rather than throwing it away, making it far more efficient than your ordinary electric motor.
As a side note, the difference between a motor and an engine is that a motor rotates, an engine reciprocates. You can indeed have an electric engine (theyre usually called "solenoids") and a gasoline motor (Mazda had "rotary engines" back in the '70s; they were actually gasoline motors.)
Free Martian Whores!
As a side note, the difference between a motor and an engine is that a motor rotates, an engine reciprocates.
Huh. I didn't know that.
Not surprising that you didn't know that, since it isn't true.
An engine is a machine that does work using a source of energy like the coiled rope of a catapult or the tank of gas for your internal combustion engine.
A motor is an engine that moves something, like, say, a motorcycle.