The electric eel is a fascinating animal that is able to generate electric shocks intense enough to defend itself from predators or subdue its prey. This amazing ability is the source of inspiration for a new technology that could power critical devices like implantable health monitors.
Researchers at the Adolphe Merkle Institute of the University of Fribourg in Switzerland have recently developed a transparent electrical device comprised of cells containing hydrogel and salt, creating an artificial electric organ that mimics the electric eel.
“The eel polarizes and depolarizes thousands of cells instantaneously to put out these high voltages,” said study co-author Max Shtein, University of Michigan associate professor of materials science and engineering. “It’s a fascinating system to look at from an engineering perspective—its performance metrics, its fundamental building blocks, and how to use them.”
The electric eel uses a process called transmembrane transport to produce its electricity. Its electric organs contain thousands of alternating compartments with either potassium or sodium ions. The compartments are separated by selective membranes, which, when activated, allow the ions to flow together to create electricity.
The system designed by the researchers instead uses sodium and chloride, dissolved in water-based hydrogel. The gel is distributed in droplets over a plastic sheet using a specialized printer, alternating with hydrogel droplets of pure water to emulate the eel’s alternating compartments.
To keep the compartments separate, the researchers used a second sheet of alternating droplets, made of charge-selective hydrogel. Each droplet allows either positively charged sodium or negatively charged chloride to pass, but excludes the other.
The two sheets are pressed together to generate power by connecting saline and freshwater droplets across the charge-selective droplets in a series. As the solutions mix, the charge-selective droplets move the sodium and chloride ions in opposing directions, producing an electric current.
However, the researchers still faced the challenge of mimicking the eel’s ability to shuffle ions instantaneously to produce jolts.
Shtein and a number of graduate students solved this problem with an origami technique called a Miura fold. Invented by a Japanese astrophysicist, the technique is often used to fold solar panels into satellites at launch, then unpack them into large sheets once they’re in space.
Shtein and his team used this technique in reverse, alternating four droplet types in a precise pattern on a flat sheet that had been laser-scored in a Miura pattern. When pressure was applied, the sheet quickly folded together and stacked the cells in the necessary positions.
“The electric organs in eels are incredibly sophisticated; they’re far better at generating power than we are,” said Michael Mayer, professor of biophysics at the University of Fribourg and an author of the paper on the device. “The important thing for us was to replicate the basics of what’s happening.”
The device is capable of generating over 100 volts and can produce a steady, low current that is capable of powering a pacemaker. The team is working to improve the device’s efficiency.
Mayer believes it may also lead to bioelectric systems that can generate electricity from naturally occurring processes inside the body.
The research was funded by the Air Force Office of Scientific Research and the National Institute of General Medical Sciences of the National Institutes of Health.
To learn more, visit Adolphe Merkle Institute of the University of Fribourg website.