Graphene-based microbattery could power biotelemetry implants
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Scaling down electronics isn’t only important when building consumer devices, it also has a hufe impact on the world of implantable medical devices. However, as with all things technological, batteries just aren’t keeping up with all the other components. It is possible to build incredibly small sensor packages that can be injected into the body, but the tiny silver oxide watch batteries most devices use just don’t allow for long-term study. This problem might be solved by everyone’s favorite form of carbon, graphene. A new type of graphene microbattery could kick off a new age of long-term biotelemetry.
If a doctor or scientist needs to track some aspect of a person’s health, they either need to be hooked up to an external machine, or there needs to be something implanted in the patient’s body — for example blood glucose and cardiac monitors. These devices are usually very short lived or much larger than they would otherwise be due to power requirements. Work on miniaturizing implantables relies on smaller, more efficient batteries like the graphene cell created by researchers at Pacific Northwest National Laboratory (PNNL).
The PNNL battery was developed for an experiment following the development of adolescent salmon. Existing implantable sensors didn’t last long enough to keep relaying data over the course of the fish’s migration, so the researchers looked into building something better. In the process of chasing the perfect implantable fish sensor, the team designed a so-called “jelly roll” microbattery based on a graphene cathode.
The form of graphene used in the PNNL battery is known as fluorinated graphene. The application of fluoride to graphene enhances its electrochemical properties allowing it to retain higher voltages and discharge more efficiently. The microbattery design is referred to as a jelly roll because the various components are laid out flat in a stack during construction. There is the fluorinated graphene cathode and a lithium-based anode, each with separating layers in between. The entire stack is then rolled up into a cylinder and sealed, thus a jelly roll.
This design allows for a significant increase in the total surface area of cathode and anode, meaning higher capacity. Even in this first iteration, the researcher managed to double the capacity of other microbatteries, and this cell is even smaller than most — about the size of a grain of rice. The battery is capable of sending out a 744-microsecond pulse every five seconds for a month. That’s more than sufficient to gather biotelemetry data over the long term.
If these tiny batteries can be developed into a reliable component in human medicine, they could absolutely save lives. Patients with medical conditions that require monitoring could get real time updates, and may not need to spend as much time in the hospital. Having fewer people in hospitals simply for monitoring reduces the risk of nosocomial (hospital-acquired) infections.
However, there is still work to be done on the design of PNNL’s batteries. Each one for the fish study was hand made from sheets of the individual components. Other teams are sure to look more closely at fluorinated graphene batteries now.