An international team of engineers from Penn state University, University Park, PA, and King Abdullah University of Science and Technology, Saudi Arabia, have discovered that saliva-powered micro-sized microbial fuel cells can produce minute amounts of energy—enough to run on-chip applications, they say. This technology may be enough to fuel glucose monitoring for diabetics.
Microbial fuel cells (MFCs) create energy when bacteria break down organic material producing a charge that is transferred to the anode. By producing nearly 1 microwatt in power, this saliva-powered, micro-sized MFC already generates enough power to be directly used in microelectronic applications, they reported in Nature Publishing Group's Asia Materials.
The researchers believe that the emergence of ultra-low-power chip-level biomedical electronics, devices able to operate at sub-microwatt power outputs, will soon become a reality. One possible application would be a tiny ovulation predictor based on the conductivity of a woman's saliva, which changes five days before ovulation. The device would measure the conductivity of the saliva and then use the saliva for power to send the reading to a nearby cell phone.
Biomedical devices using micro-sized microbial fuel cells would be portable and have their energy source available anywhere. However, saliva does not have the type of bacteria necessary for the fuel cells, and manufacturers would need to inoculate the devices with bacteria from the natural environment.
This micro version uses a single chamber with a graphene-coated carbon cloth anode and an air cathode. Air cathodes have not been used before because if oxygen can get to the bacteria, they can breathe oxygen and do not produce electricity, they said.