Eel power promises robotics boost


Mimicking the shocking power of electric eels opens the way to new power sources. Andrew P Street reports.


An electric eel: could this be the new face of soft robotics?
An electric eel: could this be the new face of soft robotics?
Reinhard Dirscherl / getty Images

There are few adjectives that grab attention like “electric-eel-inspired”, especially when it comes to powering the next generation of technology. And that is what a team of researchers from the University of Fribourg in Switzerland have developed, according to a paper in the journal Nature.

The paper, titled An electric-eel-inspired soft power source from stacked hydrogels, outlines a potential mechanism for harnessing chemical energy by copying the method by which electric eels generate electricity in their own cells.

Before any biologists write in, the name “electric eel” is a misnomer. The species, Electrophorus electricus, isn’t an eel at all, but a species of knifefish. (And before any cultleryologists write in, knifefishes are not technically knives.)

The way the titular ability of the electric eel works in nature is that the outside of their electrogenic cells have a negative charge of slightly under 100 millivolts compared with the inside of the cell. The release of the neurotransmitter acetylcholine creates a momentary path of low electric resistance between the inside and outside of the cell, allowing a current to be generated.

The cells themselves are stacked along the body of the eel not unlike the way batteries are laid in a torch. Together, the millions of cells create around 100 volts of charge, and a jumble of nerve pathways impose a delay of up to two milliseconds on the cells closest to the brain in order that the signal hits the cells simultaneously.


The Swiss researchers, led by Michael Mayer, mimicked this mechanism by using a repeating sequence of four hydrogels to replicate the operation of the electrocytes: first a high-salinity hydrogel, then a cation-selective gel, a low-salinity gel, and an anion-selective one to form ionically conductive pathways. By developing a carefully folded structure for these tubular systems they were able to control the electrical discharge, achieving the simultaneous firing of cells to produce eel-level voltages.

The result is a sophisticated but remarkably simple model which seems easily scalable. The researchers predict that advances in microfluidics promise “an artificial electric organ with 2,500 gels to generate 100V could be assembled in less than two minutes.”

The potential applications for systems that are biologically compatible are nearly endless, from medical implants to wearable tech – including display functionality in contact lenses (which, conveniently, are already made using hydrogels).

However, the supervillain dream of harnessing the power of eels to shock passers-by seems still to be out of reach – at least, for now.

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Andrew P Street is a widely published journalist, non-fiction author and former columnist for the Sydney Morning Herald.
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