An engineer at Purdue University in Indiana has designed a new kind of medical patch that is powered by yeast farts.

The patch is designed to transfer drugs into the body by reacting with body heat. The power of the patch comes from carbon dioxide produced by ordinary baker's yeast. During tests, researchers inject water into the pump before placing the
pump on someone's skin. The body heat was found to be sufficient in
activating the yeast.
Using this method, the patch will be able to efficiently deliver medicine without the need of a power source. More details from
Discovery:
The carbon dioxide eventually inflates the yeast-and-sugar chamber of
the pump bubble, putting pressure on the other chamber to pump out some
of its drug. Ziaie and a doctoral student studying with him, Manuel
Ochoa, built a half-inch (15 millimeters) prototype that pumps
continually for more than two hours, they reported in August in the
journal Lab on a Chip. Ziaie envisioned people just throwing away the
patch after the reaction was over.
A yeast-powered pump may be less bulky than battery-powered pumps
other researchers have made, Ziaie said. Yeast fungi also are able to
live for a long time in a dried state, so patches using a yeast pump
should last a long time.