Bacteria-fuelled batteries can be of great value in providing (some) electricity in environments where there is none. Useful for low-energy equipment, for example. Earlier, concept batteries were developed that 'ran' on dirty water; the most recent variant is one that uses only spit and body fluids. One spit appears to be enough to light an LED lamp.
Such bacteria-based batteries operate on so-called microbial fuel cells. These cells deploy bacteria for reduction/oxidation reactions. This involves swapping electrons back and forth between molecules and making electricity. For spit-based paper-based batteries, microbial fuel cells are deployed from inactive, freeze-dried exoelectrogenic cells. These can be stored for a long time and generate energy within minutes after being spit on. Freeze-drying technology is employed to store the bacterial cells in the battery for a long time.
During tests, a power density of a few microwatts per square centimetre was achieved. That is enough to turn on an LED lamp. It is envisaged that the equipment could eventually be used to power disposable diagnostic equipment that would need a few tenths of microwatts.
Source: Newatlas.com
