A micro-jet engine in your cell phone

A bit old season (fall 2004), but still stunning: Miniature jet engines could power cellphones:

Engineers have moved a step closer to batch producing miniaturised, jet engine-based generators from a single stack of bonded silicon wafers. These chip-based “microengines” could one day power mobile electronic devices.

By spinning a tiny magnet above a mesh of interleaved coils etched into a wafer, David Arnold and Mark Allen of the Georgia Institute of Technology, US, have built the first silicon-compatible device capable of converting mechanical energy - produced by a rotating microturbine - into usable amounts of electrical energy. The key advantage of microengines is that they pack in at least 10 times more energy per volume of fuel than conventional lithium batteries, take up less space and work more smoothly than much-touted fuel cells. (...) The US Army expects that soldiers - who currently rely on battery-powered laptops, night-vision goggles and GPS systems - will be the first to use the microengines.