Implantable battery could run on the body’s own oxygen

Researchers led by the Tianjin University of Technology have recently developed an implantable battery that operates on the body’s own oxygen, a novel approach that could revolutionize the powering of medical devices such as pacemakers and neurostimulators. The study, conducted on rats, demonstrates the battery’s potential for stable power delivery and biological compatibility.

The body as a continuous energy source

“Implantable electronics have transformed disease diagnostics, therapies, wound healing, and health monitoring,” wrote the researchers. “The reliable operation of these devices depends on the performance of implantable batteries that possess good bio-compatibility and sufficient capacity.” “Conventional batteries, such as Li-I2 and Ag-Zn batteries, are sealed and utilized for powering implantable devices. However, their capacities are restricted by the mass of active Li/I2 or Ag/Zn embedded in the batteries, which limits their service life.” “Living organisms contain a wealth of basic components that can be used as continuous energy sources for batteries, including dissolved oxygen, glucose, enzymes, and sweat.”

Implantable battery interacts with oxygen in the body

“When you think about it, oxygen is the source of our life. If we can leverage the continuous supply of oxygen in the body, battery life won’t be limited by the finite materials within conventional batteries,” said corresponding author Xizheng Liu, an expert in energy materials and devices at Tianjin University. The battery’s electrodes, made from a sodium-based alloy and nanoporous gold, interact chemically with bodily oxygen to generate electricity. To ensure safety and flexibility, the battery is encased in a porous polymer film.

Testing the Implantable battery

Implanted under the skin of rats, the battery maintained voltages between 1.3 V and 1.4 V, achieving a power density of 2.6 µW/cm^2 over two weeks. While currently not powerful enough for medical devices, this demonstrates the feasibility of using internal oxygen for energy generation. The research team found no significant inflammation in the rats. The battery’s byproducts, including sodium and hydroxide ions and a minimal amount of hydrogen peroxide, were effectively processed by the body, causing no harm to the kidneys or liver. Surprisingly, the implantation site showed complete hair regrowth and blood vessel regeneration around the battery after four weeks.

Implantable battery and wound healing

“We were puzzled by the unstable electricity output right after implantation. It turned out we had to give the wound time to heal, for blood vessels to regenerate around the battery and supply oxygen, before the battery could provide stable electricity. This is a surprising and interesting finding because it means that the battery can help monitor wound healing,” Liu explained. Currently, the scientists aim to enhance the battery’s energy output by investigating more efficient materials and optimizing its structure. According to Liu, this battery also has significant potential for scaling and cost-effectiveness.

New revolution in the field of implantable devices

“The O2 concentration in the present battery can be controlled precisely and thus has the potential of therapeutic capabilities against diseases caused by oxygen aggregation or pathogenic bacteria,” wrote the study authors. “The catalysts in cathode of Na-O2 battery can also reduce the super-oxide radicals that cause cellular senescence and dementia, highlighting its potential applications in these fields.” “While several fundamental studies and intrinsic challenges remain to be tackled, the Na-O2 battery is still highly promising and can spark a new revolution in the field of implantable devices, leading to the development of new methods for the treatment of various diseases.”

Potential medical applications

The implantable battery could provide new therapeutic strategies, such as targeting tumor cells by depleting oxygen or converting energy to heat to kill cancer cells. “Because tumor cells are sensitive to oxygen levels, implanting this oxygen-consuming battery around it may help starve cancers. It’s also possible to convert the battery energy to heat to kill cancer cells. From a new energy source to potential biotherapies, the prospects for this battery are exciting,” Liu concluded. The study is published in the journal Chem.