(CN) — For those who depend on implanted medical devices like pacemakers, battery life is crucial, but when the batteries currently used by doctors inevitably run out of juice, replacing the power source means invasive surgeries and risk to the patient.
In a Wednesday study, however, researchers from China think they may have found an alternative in the form of a new type of battery powered by oxygen already 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," study co-author Xizheng Liu, a specialist in energy materials and devices at China's Tianjin University of Technology, said in a statement
The researchers, in a study published Wednesday in the journal Chem, created and successfully tested in animal studies what they called an “implantable, flexible, and bio-compatible” battery that could last much longer than existing kinds of batteries for pacemakers, neurostimulators or other implanted medical devices.
According to the study team — which included researchers from Tianjian University, Fudan University and Hebei University — the battery uses a porous casing to let oxygen-rich blood act as a component of the battery, massively extending the potential lifespan of the battery while providing “extremely high energy densities that are 5-10 times greater than currently available batteries."
The oxygen in the blood works alongside the battery’s solid components — a nanoporous gold electrode and a sodium-alloy electrode made of sodium, gallium and tin, separated by an ion-selective membrane. All this is encased in another flexible, porous polymer film, and would be attached to a medical device by gold wires.
After finalizing the design, the team implanted the batteries beneath the skin on several rats’ backs and measured the output at several time periods after the procedure: 2 hours, 24 hours, 2 weeks and 4 weeks.
After an hiccup in the form of unstable electricity output after the battery was initially implanted, with an abrupt voltage drop at 2 hours and unstable voltage at 24 hours, the 2-week and 4-week tests put the project back on track.
“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," Liu said. "This is a surprising and interesting finding because it means that the battery can help monitor wound healing.”
Once they healed, the capillaries provided plenty of oxygen to fuel the batteries, which stabilized around 1.3 volts and a maximum power density of 2.6 microWatts per square centimeter in the 2-week and 4-week tests.
The team also noted that the tested rats showed no inflammation from the batteries’ reaction and successfully metabolized any byproducts, like sodium, hydroxide and hydrogen peroxide ions.
While their prototypes did not provide sufficient power output for medical devices like pacemakers, it nonetheless marked a success for the team, who say this is proof of concept that oxygen can be used as a power source.
Liu and the team also see promise for the new battery technology in other fields. Since the concentration of oxygen can be precisely controlled, the battery can regulate oxygen flow to parts of the body, meaning the technology could even be used to keep oxygen away from 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,” says Liu. “From a new energy source to potential biotherapies, the prospects for this battery are exciting.”
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