Mimicking electric eel cells to produce energy
A team of U.S. engineers has found that it's possible to build artificial cells replicating the electrical behavior of electric eel cells. In fact, these artificial cells deliver better performance than the real ones, called electrocytes, which can generate electric potentials of up to 600 volts. The researchers have developed a computer model which suggests that these future artificial cells could generate as much as 40% more energy than the eels' ones. The research team thinks that their artificial cells could be used to power medical implants and other small devices. Read more...
You can see above some details about the electric eel anatomy. "The first detail shows stacks of electrocytes, cells linked in series (to build up voltage) and parallel (to build up current). Second detail shows an individual cell with ion channels and pumps penetrating the membrane, The Yale/NIST model represents the behavior of several such cells. Final detail shows an individual ion channel, one of the building blocks of the model." (Credit: Daniel Zukowski, Yale University) Here is a link to a NIST page containing several versions of this illustration at various resolutions.
This project has been led by NIST engineer David LaVan and Yale University scientist Jian Xu. It's usual that U.S. government employees don't have a web page, but it's less common for university researchers.
Let's look now at the purpose of this project. "Electric eels channel the output of thousands of specialized cells called electrocytes to generate electric potentials of up to 600 volts, according to biologists. The mechanism is similar to nerve cells. The arrival of a chemical signal triggers the opening of highly selective channels in a cell membrane causing sodium ions to flow in and potassium ions to flow out. The ion swap increases the voltage across the membrane, which causes even more channels to open. Past a certain point the process becomes self-perpetuating, resulting in an electric pulse traveling through the cell. The channels then close and alternate paths open to “pump” the ions back to their initial concentrations during a 'resting' state."
Different cells have different functions. For example, "nerve cells, which move information rather than energy, can fire rapidly but with relatively little power [while] electrocytes have a slower cycle, but deliver more power for longer periods." The research team "developed a complex numerical model to represent the conversion of ion concentrations to electrical impulses and tested it against previously published data on electrocytes and nerve cells to verify its accuracy. Then they considered how to optimize the system to maximize power output by changing the overall mix of channel types."
And what did the researchers find? "Their calculations show that substantial improvements are possible. One design for an artificial cell generates more than 40 percent more energy in a single pulse than a natural electrocyte. Another would produce peak power outputs over 28 percent higher. In principle, say the authors, stacked layers of artificial cells in a cube slightly over 4 mm on a side are capable of producing continuous power output of about 300 microwatts to drive small implant devices."
This research work has been published by Nature Nanotechnology under the title "Designing artificial cells to harness the biological ion concentration gradient" (Advance online publication, September 21, 2008). Here is the beginning of the abstract. "Cell membranes contain numerous nanoscale conductors in the form of ion channels and ion pumps that work together to form ion concentration gradients across the membrane to trigger the release of an action potential. It seems natural to ask if artificial cells can be built to use ion transport as effectively as natural cells. Here we report a mathematical calculation of the conversion of ion concentration gradients into action potentials across different nanoscale conductors in a model electrogenic cell (electrocyte) of an electric eel."
The researchers add that by "using the parameters extracted from the numerical model, we designed an artificial cell based on an optimized selection of conductors. The resulting cell is similar to the electrocyte but has higher power output density and greater energy conversion efficiency. We suggest methods for producing these artificial cells that could potentially be used to power medical implants and other tiny devices."
Now, it remains to be seen when medical implants based on this project will come to our bodies.
Sources: National Institute of Standards and Technology (NIST), October 2, 2008; and various websites
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