At InsideEVs when we talk about batteries, we almost always refer to those related to mobility, but batteries are now used in so many fields, including medicine. They are used to power pacemakers, neurostimulators and other devices that allow us to live better, regulating the functioning of the heart or alleviating pain, for example.

Lo and behold, the batteries that are implanted inside the human body, like all the others, run out and have to be replaced by surgery that, in some cases, is quite invasive and complicated. At least, that is what has happened so far, but things may be different in the future.

A technology without contraindications

In fact, a team of Chinese researchers has invented a battery that recharges itself using the oxygen flowing through the body. The study, which was published in the journal Chem, went into great detail on how the battery was made, which has electrodes made of an alloy of sodium and nanoporous gold that can initiate chemical reactions by interacting with oxygen.

The researchers implanted the battery under the skin of laboratory mice, wrapped it in a porous, soft and flexible polymer film, and measured its electricity production. After two weeks, they found that the battery can produce stable voltages between 1.3 and 1.4 volts, with a maximum power density of 2.6 microwatts per square centimetre.

The values recorded are not yet sufficient to power current medical devices, but they point a new way forward. Moreover, in addition to the proper functioning of the battery, it was encouraging to record the total absence of allergic reactions or inflammation, proving that this technology is biologically compatible.

The by-products of the chemical reactions taking place in the battery (production of sodium and hydroxide ions) were in fact metabolised by the body without any consequences.

It can also serve in the fight against cancer

'Come to think of it, oxygen is the source of our life,' said Xizheng Liu, a researcher at Tianjin University of Technology who led the study. 'If we can harness the continuous supply of oxygen in the body, the battery life will be infinite.

"At first we were puzzled by the unstable production of electricity immediately after implantation, but then we discovered that we just had to wait for the wound to heal, to give the blood vessels time to regenerate and start supplying oxygen. At that point, operation was smooth".

The team's next step is to study more efficient materials that can increase the energy produced. But that is not all. In the course of the research, other interesting discoveries were made. For instance, it was seen how, by implanting a battery near a wound, one can monitor its healing process. Indeed, Liu believes that this type of battery can also be used in the fight against tumours.

'Since tumour cells are sensitive to oxygen levels,' he explained, 'implanting this oxygen-consuming battery around them (brings to mind a project carried out by researchers at the University of Vienna) can help starve tumours. It is also possible to convert the battery's energy into heat to kill cancer cells. From a new energy source to potential biotherapies, the prospects for this battery are exciting'.