Correction Appended: November 6, 2007
How's this for eco-friendly: a battery that runs on sugar. Sony's bio cell, unveiled in mid-2007, uses glucose-digesting enzymes to extract electrons from any sugary solution (as with other batteries, the electrons flow around the circuit to generate electricity). Connect four of the 50-milliwatt cells, and you've got enough juice to keep your MP3 player humming.
The original version of this article stated that the Sony bio cell prototype was unveiled in mid-2008. It was actually unveiled in mid-2007.
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