Produce energy without lithium, cobalt, or toxic chemicals? This is the idea behind a brand new battery developed by a team of Chinese researchers from the Academy of Sciences, in Shenzhen. Their invention uses a well-known bacteria from the scientific world, Shewanella Oneidensis MR-1, capable of generating electricity from its biological activity.
A useful battery … but not to run a computer
The prototype is the size of a conventional button battery (20 mm in diameter, 3.2 mm thick). It works thanks to a living hydrogel, a gelatinous material which contains the famous bacteria. The latter are encapsulated in an alginate matrix (a component derived from algae), where they remain active throughout the operating period. Result: a small battery capable of producing electricity … all alone.
The whole is completed by an ion exchange membrane and a cathode containing ferricyanide. The system can be printed in 3D, with forms adapted to different uses – an asset if you target medical applications.
On the performance side, this bio-batterie will not immediately replace your smartphone. It displays a maximum power of 8.31 µw/cm², a specific capacity of 0.4 mAh/g and an energy density of 0.008 Wh/L… figures very below the current lithium-ion batteries. But this is not the objective. The idea here is to offer a cleaner alternative to supply small devices, such as medical sensors, implants or portable objects.
Another interesting particularity: the system can recharge itself, thanks to the metabolism of bacteria. The tests show that he is able to support up to ten recharging cycles, with an efficiency of 99.5 % – in other words, very little loss of energy. And above all, bacteria remain healthy: they retain viability greater than 97 % at the end of the cycles.
Researchers have also shown that this small battery could be used to electrically stimulate nerves, including the sciatic nerve and the vagus nerve. This type of controlled stimulation could ultimately play a role in medical treatments or physical therapies.
Even if it is only a prototype, this living battery shows that it is possible to produce electricity differently, with biodegradable materials and without extracting rare resources. It is one more step towards more environmentally friendly energy systems, provided that researchers find how to increase power without harming to the living.
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