A new bio friendly energy storage system has been developed by researchers from the University of Connecticut and UCLA. Called a biological supercapacitor, the device functions by using charged particles, or ions, from fluids in the human body. The device does not interfere with the body’s biological systems in any way and could spark the development of cardiac pacemakers and other implantable medical devices that last longer.

Pacemakers help regulate abnormal heart rhythms and, together with other implantable devices, they have saved numerous lives. Their biggest drawback is however that they’re powered by batteries. These eventually run flat and must be replaced. The only way in which this can be done is through painful surgery and this means risk of infection. Batteries are also made of toxic materials and if they leak, it could harm the patient.

The researchers suggest that energy could be stored in those devices without batteries. The supercapacitor they developed can charge by using the electrolytes in biological fluids like urine and blood serum. The supercapacitor could work with an energy harvester, which would convert motion and heat from the body into electricity. The principle of operation is similar to that of self-winding watches that are powered by the wearer’s body movements. The electricity that is generated could then also be stored in the supercapacitor.

Maher El-Kady, a UCLA postdoctoral researcher and a co-author of the study, believes that if energy harvesters are combined with supercapacitors, the combination could provide endless power that would result in lifelong implantable devices that might never have to be replaced.

Modern pacemakers are normally between 6 and 8 millimeters thick, and have the same diameter as a 50-cent coin. Approximately 50% of the space is used by the battery. Compared to that, the supercapacitor is only 1 micrometer thick, which is smaller than the thickness of a human hair. This means that the energy efficiency of any implantable device would be improved dramatically. The supercapacitor can also twist and bend inside a body without any mechanical damage, sustain its performance for a long time and store more energy than lithium film batteries of comparable size can.









Islam Mosa, a Connecticut graduate student and first author of the study, explained that while batteries use chemical reactions that involve electrolytes and toxic chemicals to store energy, the new bio supercapacitor stores energy by using readily available charged molecules, or ions, from the body’s fluids.

The new bio supercapacitor consists of graphene, a carbon nanomaterial, layered with an electrode made from modified human proteins. The electrode acts as a conductor through which electricity can flow to and from the energy harvester. Kaner is of the opinion that the new device could eventually lead to the development of next generation implantable devices that could be used to promote healing, speed up bone growth, or stimulate the brain.

Although supercapacitors are not yet used in medical devices widely, the study demonstrates that they could well be viable for that purpose.

El-Kady concluded by noting that for pacemakers without batteries to be effective, they need supercapacitors that are able to capture, store and transport energy. Commercial supercapacitors currently available are too slow to be effective in this application. The research done here concentrated on custom designing bio supercapacitors that are able to capture energy effectively, and finding ways to make them compatible with the human body.

The full study was published in the journal Advanced Energy Materials.