Edible batteries are still in a research stage, but should they become a reality it would offer an entirely new way to gather medical data. Material scientist Christopher Bettinger who is a professor at Carnegie Mellon University has been at the forefront of edible battery research. The goal behind this work is to be able to power sensors that could take internal readings without the need for more invasive procedures.

The challenge is in making batteries out of safe biodegradable materials. Carnegie Mellon researchers have been using various combinations of manganese oxide, sodium titanium phosphate and combining them with copper, aluminum or iron. The batteries structure is being 3D printed. The current battery pill  makes use of naturally occurring pectin (think fruit canning) as a barrier between the ions and for higher voltage stacking. Melanin derived from squid ink is being used for the electrodes. These batteries provide a maximum of 10mW of power for up to 10-20 hours. Quite a bit of progress has been made since the last time edible batteries came up. Chris has already swallowed his battery.

Sources:

Materials Advances for Next-Generation Ingestible Electronic Medical Devices

Battery you can swallow could enable future ingestible medical devices