By Mykl Ambros
The body of the electric eel, Electrophorus electricus, is 80% electricity-producing organs. Their organs have rows of electrolytes, which create voltage when positively charged sodium and potassium ions flow between and within cells. The overall direction is towards the head of the eel. This creates a difference in charge between the outside of the eel and its prey, creating a shock. While each electrocyte can only produce about 150 millivolts, when enough cells are lined up, several hundred volts can be produced.
Researchers at the University of Fribourg in Switzerland have created a chain of hydrogels which, when stacked in a certain order, produce electricity. When all of the gels in an artificial cell are in contact, positively charged sodium ions atoms move towards one end of the cell while negatively charged chlorine ions atoms move to the other end. This difference in charge creates a voltage between 130 and 185 millivolts.
Though this is an encouraging technology, there have been some problems. The current thickness of the hydrogel stacks is too great to be able to efficiently power any device. Another issue is due to discharges, as the hydrogels also have to be hooked up to an external power source in order to move the ions to their original positions. The issue of reorienting the hydrogels after discharge could be solved by taking advantage of the natural charge separations in the body, i.e. the stomach, which is more positively charged than the surrounding tissues, to produce the electricity to recharge the artificial cells.
This technology shows great promise in almost every application of implantable or wearable technology. A biocompatible self-charging power source in the body creates opportunities for advancements in pacemakers, mechanical organs, optical implants, insulin pumps, biosensors, prostheses, and anything else that uses electricity.
References:
Schroeder, T. B. H., Guha, A., Lamoureux, A., VanRenterghem, G., Sept, D., Shtein, M., Yang, J., & Mayer, M. (2017). An electric-eel-inspired soft power source hydrogels. Nature, 552, 214-218. doi: 10.1038/nature24670
Art by Vayl Sorensen