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."

Comments

Re:what is a cubic micrometer

[Red Flayer]

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.

Re:Heat engine != internal combustion engine

[Scrameustache]

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.