There's no doubt that residents of developing nations can benefit hugely from having mobile phones. This particularly applies to the field of medicine, as the phones allow people living in remote areas to contact health care practitioners, or to use health care apps. Given how unreliable the electrical grid can be in such countries, however, keeping those phones charged can be a challenge. That's why a team from the Harvard School of Engineering and Applied Sciences (SEAS) is working on a microbial fuel cell-based charger – a mobile phone charging system that gets its power from microbes in the soil.

The project is being led by Dr. Aviva Presser Aiden, an affiliate of SEAS and a current student at Harvard Medical School. Her device incorporates a conductive surface, that harvests free electrons created by naturally-occurring soil microbes during the course of their metabolic processes. She has already used the technology to power LED lights in a lab for 14 months.

Once they're ready to go, Aiden plans on distributing the chargers within a region of Sub-Saharan Africa, as part of a field study. Ultimately, however, she would like to see the local people being able to build their own, using readily-available materials such as window screens and soda cans. She believes that a complete device could be assembled from scratch in just a few minutes, at a cost of less than a dollar. It should be able to fully charge a phone within 24 hours.

Currently, over 500 million people living in Sub-Saharan Africa lack power in their homes, even though 22 percent of households in the region have mobile phones. Therefore, many people have to walk long distances to charging stations, paying between 50 cents and a dollar per charge. While solar chargers are one alternative, Aiden says that can be costly, and are often not even offered due to the lack of a distribution/repair network.

The project received a US$100,000 grant last month, from The Bill & Melinda Gates Foundation's Grand Challenges program.