When medical devices are implanted, there is often an issue with providing the device with power. There are wireless power sources available, but they are relatively bulky and are often too large for devices that are deep in the body and obstructed by muscle and bone. Putting a battery in with the implanted device is ideal, but there are some safety considerations involved. However, a new battery developed by John Rogers of the University of Illinois at Urbana-Champaign is biodegradable and dissolves completely . The battery was described in full in the journal Advanced Materials.

The anodes of the battery are made out of magnesium foil, while the cathode can either be iron, tungsten, or molybdenum. The electrolyte is made of a phosphate-buffered saline, and the entire thing is encased in a biodegradable polymer shell. At the rate that these substances will degrade in the body, the ions generated by the metals and the other materials are in low enough concentrations so they are safe and biocompatible, according Rogers. The cell of the battery measures about one square centimeter.

There are other batteries in development seeking to achieve biocompatibility, including one by Christopher Bettinger from Carnegie Mellon which is a sodium-ion battery with electrodes generated from cuttlefish ink. However, Rogers’ device outperforms it. Currently, the battery is able to offer 2.4 milliamps of steady current for about a day. With further development, Rogers believes that the battery could be reduced to about a quarter of its current size without affecting its output. 

Aside from biological implants, these batteries could be used for environmental purposes, like after oil spills. Hundreds of these biodegradable batteries could accompany biodegradable sensors, such as one his team developed in 2012, in order to collect information about the pollution in the ocean water which would expedite clean-up efforts. Because size would be less of an issue, larger batteries with a greater output could be developed. After scientists have collected the data, the equipment could just dissolve into the water.

Battery completely dissolving in water over the course of three weeks. Credit: Rogers et al.