Batteries designed to run on oxygen from inside the body could last months or years before needing to be recharged or replaced, and might one day power everything from pacemakers to brain implants.
at Tianjin University of Technology in China and his colleagues made their batteries from a sodium-based alloy and a porous form of gold, taking advantage of the fact that sodium reacts with oxygen to create electrical power. That means these batteries can be implanted in the body and exploit the constant flow of oxygen to produce a current. The resulting waste products 鈥� sodium ions and hydroxide ions 鈥� are absorbed by the body.
The researchers tested the batteries by placing them beneath the skin of rats. Initially, they produced unstable voltages, but the team soon realised that blood vessels needed to regrow around the battery in order to bring oxygen close enough for the chemical reaction to occur. After allowing for two weeks of healing, tests showed that the batteries produced a stable voltage between 1.3 and 1.4 volts. The rats showed no signs of inflammation, and the byproducts were metabolised by the body and seemingly caused no ill effect.
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These prototype batteries don鈥檛 produce a high enough current to power medical devices, but the researchers say that the experiment proves that harnessing oxygen in the body for energy is possible, and they believe efficiency improvements can be made.
While an upgraded version of such a battery could power implants for extended periods of time, eventually the sodium electrode would be used up by the chemical reaction. 鈥淭his battery cannot last forever,鈥� says Liu. 鈥淕enerally, the service life of [a] battery depends on the total mass of cathode and anode in the battery.鈥�
The next steps are to experiment with more efficient materials and structures to eke out more voltage, and also to conduct experiments on the safety of the device against human skin and internal organs prior to full human trials, says Liu.
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