Researchers have designed a new bio-friendly energy storage system called a biological supercapacitor. This works by using charged particles, or ions, from fluids in the human body. The device is harmless to the body’s biological systems and may lead to longer-lasting cardiac pacemakers and other implantable medical devices.
Pacemakers help to regulate abnormal heart rhythms; other implantable devices have also saved countless lives. However, they all need to be powered by traditional batteries which will eventually run out of power and must be replaced.
This means the patient requires another painful surgery, and with that comes the accompanying risk of infection. There are also additional dangers; batteries also contain toxic materials that could one day leak, endangering the patient.
The researchers suggest storing energy in those devices without using a battery. They have invented a supercapacitor that charges by using electrolytes from biological fluids such as blood serum and urine.
The supercapacitor would work with another device called an energy harvester. This device converts heat and motion from the human body into electricity (The same way that self-winding watches are powered by the wearer’s body movements) which would then be captured by the supercapacitor.
Maher El-Kady, a UCLA postdoctoral researcher and a co-author of the study, said in a statement:
“Combining energy harvesters with supercapacitors can provide endless power for lifelong implantable devices that may never need to be replaced.”
The new supercapacitor is only 1 micrometer thick (smaller than the thickness of a human hair) where modern pacemakers are typically around 6 to 8 millimeters thick, and are close to the diameter of a 50-cent coin; about half of that space is usually occupied by the battery. This could mean that the new supercapacitor could improve implantable devices’ energy efficiency.
It can also maintain its performance for a longer time and can bend and twist inside the body without any mechanical damage. The new supercapacitor can also store more charge than the lithium film batteries that are currently used in pacemakers. Islam Mosa, a Connecticut graduate student and first author of the study, said:
“Unlike batteries that use chemical reactions that involve toxic chemicals and electrolytes to store energy, this new class of biosupercapacitors stores energy by utilizing readily available ions, or charged molecules, from the blood serum.”
Richard Kaner, a member of UCLA’s California NanoSystems Institute and who led the UCLA team said:
The new biosupercapacitor consist of a carbon nanomaterial called graphene layered with modified human proteins as an electrode, a conductor through which electricity from the energy harvester can enter or leave. The new platform could eventually also be used to develop next-generation implantable devices to speed up bone growth, promote healing or stimulate the brain.
Supercapacitors have yet to be widely used in medical devices; however the study shows that they may be viable for that purpose. El-Kady explained:
“In order to be effective, battery-free pacemakers must have supercapacitors that can capture, store and transport energy, and commercial supercapacitors are too slow to make it work.
“Our research focused on custom-designing our supercapacitor to capture energy effectively, and finding a way to make it compatible with the human body.”
The UCLA team was led by Richard Kaner, a distinguished professor of chemistry and biochemistry, and of materials science and engineering, and the Connecticut researchers were led by James Rusling, a professor of chemistry and cell biology. A paper about their design was published in the journal Advanced Energy Materials.
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