Mimicking Electric Eels to Provide Power to Medical Devices
While the shock of an electric eel sounds like more of a medical nightmare than a fortunate asset, researchers at the University of Michigan were inspired to simulate the power of these slick creatures in hope of creating power sources for a variety of medical devices. With society’s heavy reliance on technology, it’s not surprising that medical treatments have continued to rely more and more on electrical devices including wearable and implantable sensors, pacemakers, and prosthetics. Just as with any piece of technology, these devices require an electrical power source. However, medical devices face the added requirement of being biocompatible, meaning they must function safely and effectively in the human body. Eel-inspired power sources may achieve this goal of being biocompatible while supplying medical devices with the electricity they need to function.
The inspirational efficiency with which an eel uses its electrical shock, to help catch prey and protect itself against predators, is the result of natural selection. Electrophorus electricus, know commonly as a knifefish or an electric eel, possesses an electric organ that extends through the back 80% of its body. The organ contains parallel stacks of special cells called electrocytes. When a situation arises that warrants a shock from the eel, its nervous system generates an electric current by activating thousands of electrocytes at the exact same time. As the cells are activated, the positively charged sodium and potassium ions, in and around the cells, move toward the head of the eel. The movement of these ions allows each of the electrocytes to act like small batteries. The activated end that lost the ions has a negative charge, while the opposite side that acquired the sodium and potassium ions carries a positive charge. The battery-like cells can each generate a small, innocuous voltage (less than that of a AAA battery). But when combined, the eel’s shock can be over 600 volts! For reference, a US household outlet supplies 120 volts. While a significant portion of this voltage is lost to the water around the eel, its prey or attacker will still get a nasty shock.
The University of Michigan team has successfully created an artificial electric organ that can potentially be used by humans to power devices. To make the electrical power supply biocompatible, it was necessary to efficiently mimic the features of the eel’s electric organ. This was achieved by preparing hydrogel membranes that could be layered to replicate the structure of the organ. To mimic the movement of ions in and out of the cells, the hydrogels were filled with dissolved table salt, which is made of sodium and chlorine ions. Half of the cells were designed to allow only positively charged sodium ions out and the other half would only allow negatively charged chlorine ions to exit. The gels containing the salt water were alternated on the membrane sheet with gels containing pure water, which allows the sodium and chlorine to move in opposite directions. This flow of ions generates an electric charge with an electrical potential of 110 volts. While this voltage is less than that of the inspirational eel organ, in its current state the artificial organ may be sufficient to power some low-power devices.
Though pleased with the engineering of a potentially biocompatible power source, the researchers acknowledge that there are plenty of opportunities to improve its design. By increasing the efficiency of these artificial organs, researchers believe their utility will increase, as they will become more suitable for use in combination with implantable devices.
Peer edited by Erika Van Goethem.
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