Rotary fans can be too large for applications like hand held computers or
cellphones, and may require more power than can be provided by a battery
operated device. Piezo Technologies proprietary piezoceramics make the emerging
field of Piezo Fan technology more realistic than ever for commercial
applications. The new ceramics provide higher performance in deflection for a
given size and power requirement than any other piezoceramic available claim Piezo Technologies.
"Piezo fans work on a simple principle. The piezo fan has a flexible blade, typically made of mylar, that is set into motion by a piezoceramic bending element. This bending element functions due to an ultra low power oscillating current of electricity. The electric field causes the piezoceramic to elongate, which bends the blade back and forth. The rapid flapping action produced is much like that of a humming bird’s wing, and creates an enormous amount of cooling capacity.
A more technical description would be that alternating currents cause piezoelectric ceramics to bend a blade element. High-amplitude resonant vibration of the blade creates a channeled air flow that is used for ultra-efficient cooling. The length and thickness ratios of the piezoceramics and the blades used play an important role in the cooling effectiveness."
The actual Pizeo fan pictured above is from the manufacturer Piezo Systems. To put things in perspective it operates
on 115VAC/60Hz, moves about 2 CFM airflow(0.9 l/s), produces a peak air velocity
of 400 FPM (2 m/s), weighs just 2.8 grams and costs about $150USD in single
FULL STORY @ PIEZOFANS (http://www.piezofans.com/piezofans.php)