The problem with current piezoelectric systems is that they're typically made from toxic materials. But boffins at the Berkeley Lab have devised an ingeniously green alternative—current-creating bacteriophages.
The M13 bacteriophage virus normally spends its time infecting and replicating within E. coli bacteria. However, it also has a couple of handy perks including the ability to generate electric current when compressed, readily replicate, and also a habit of aligning itself into orderly rows.
Berkeley Lab scientists shoehorned this virus into battery form by stacking 20 layers of a genetically-modified version of M13 atop a gold substrate and attaching leads. The result—a tiny battery able to output six nanoamperes at 400 millivolts. Granted, that's a very small amount of current—like, snail generator-levels of charge—but still.