In the future of implantable medical devices, batteries could “breathe” just like us. A team of researchers has designed an innovative implantable and bio-compatible Na-O2 battery. This pioneering device uses oxygen dissolved in body fluids as the active component of the cathode, promising a long-term energy source to power a variety of medical applications. And it wasn't easy to get there.
A breath of energy
How about a pacemaker that doesn't need to be replaced every few years? Or a neurostimulator that works continuously without having to worry about charging? These scenarios, until yesterday science fiction, are a little closer thanks to the implantable Na-O2 battery developed by the research team led by Yang Lv e Xizheng Liu from Tianjin University of Technology, China.
You can learn more about the study here.
The idea behind it? It's as simple as it is ingenious: exploit the oxygen already present in the tissues as "fuel" for the battery. In practice, this battery "breathes" the O2 dissolved in body fluids, a bit like our lungs do when they inhale air and transfer it to the blood.
Anatomy of a living battery
But how do you build a battery that works in symbiosis with the human body? It's certainly not a walk in the park. Special materials, ingenious architectures and a good dose of bio-compatibility are needed.
The heart of this Na-O2 battery is the cathode, consisting of a nanoporous gold (NPG) catalyst that facilitates the oxygen reduction reaction. In practice, this spongy material captures O2 from fluids and turns it into electricity.
On the other side is the anode, composed of an alloy of sodium, gallium and tin (NaGaSn) that acts as an electron reservoir. This innovative material overcomes the safety and stability problems of pure metallic sodium, which would tend to degrade rapidly in the biological environment.
To keep the two electrodes separate there is an ion exchange membrane (Nafion) which acts as a protective barrier. Everything is enclosed in a soft and bio-compatible casing made of poly-L-lactate-co-caprolactone (PLCL), a material that the body tolerates well and which allows the creation of a flexible and implantable battery.
In summary: an electrochemical jewel. A device in which each component is designed to work in harmony with living tissues, without triggering adverse reactions or inflammation.
Implantable battery, energy for life
I'll say it in a nutshell: this drum set is not an exercise in style. Its application potential is enormous and concrete. During animal model testing, the device implanted in rats demonstrated stable and long-lasting electrochemical performance, with a power density of 2,6 μW/cm2 at 1,3 V for over 4 weeks.
This means that the implantable Na-O2 battery could continuously power a variety of medical devices, from pacemakers to neurostimulators, from glucose sensors to drug delivery systems. Devices that today require frequent replacement or external recharging, with all the resulting inconveniences and risks for the patient.
Not only that: the battery discharge reaction involves a consumption of O2 from body fluids, which could have a therapeutic effect in itself. Yes, because in some pathological contexts, such as solid tumors or anaerobic infections, tissue hypoxia is an aggravating factor. By withdrawing some oxygen from these areas, the battery could create an environment less conducive to the growth of diseased cells.
It's a bit like every doctor's dream: an implantable device that not only monitors and stimulates, but also treats in a synergistic way. A sort of metabolic "pacemaker" that also rebalances the biochemistry of the tissues.
The challenge of bio-compatibility
Of course, the road ahead is still long and full of obstacles. The main challenge to disseminate this technology is to ensure its complete bio-compatibility and long-term safety. You cannot implant something in a human body that sooner or later causes problems.
During experiments on rats, the implantable Na-O2 battery showed excellent tolerability, without causing significant inflammation or immune reactions. The discharge products, mainly Na+ and OH- ions, are efficiently disposed of by the kidneys and liver without altering homeostasis. Furthermore, new capillaries have formed around the cathode which guarantee a constant supply of O2, demonstrating the perfect integration of the device into the host tissues.
But rats are not people, and testing an implantable battery in humans requires extremely high safety standards and rigorous experimental protocols. You need to be sure that each component is stable and does not release toxic substances in the long term. It is necessary to verify that the performances remain constant over time and that there are no dangerous electrochemical drifts. And the interface between device and tissues must be carefully managed to avoid fibrosis or rejection.
All questions that will still require a lot of interdisciplinary work, between materials scientists, electrochemists, biomedical engineers and clinicians. But the premises are exciting.
Implantable battery that “breathes”: towards a symbiotic future
What would he think Luigi galvani, the pioneer of electrophysiology, faced with this union between chemistry and electricity in living systems? He who, observing the frog legs shaken by the current, was the first to understand the intimate relationship between biological and electrical phenomena. Perhaps, seeing an implantable battery that "breathes", after recovering from his amazement he would smile smugly.
Or perhaps, as an anatomist that he was, he would be amazed at how the human body can accommodate and power an artificial device. Like a mother feeding her baby, our tissues offer oxygen and stability to this electrochemical creature, in a perfect symbiosis between organic and inorganic.
Is it a bit like the post-human dream of cyborgs and transhumanists, to overcome the limits of biology with the help of technology? Or is it simply an older and deeper vision, which has its roots in the co-evolution between life and matter?
After all, our cells are tiny batteries that breathe oxygen and “pump” energy. This implantable battery takes to the extreme a principle that nature has always known.
Of course, there will still be much to do and discuss. Ethical, regulatory, social and existential issues to address. But one thing is certain: with this innovation, the boundary between energy and life becomes thinner. And the future of implantable medical devices takes on a new, electrifying breath.
