A hydrogel device inspired by electric eels could convert chemical energy from the body into electricity to power wearable and implantable devices.

A research team led by Michael Mayer from the University of Fribourg, along with researchers from the University of Michigan and UC San Diego, developed a device that produced 110 volts from gels filled with water, known as hydrogels.

The team hopes their results will one day help develop power sources for implantable devices that can ‘utilise the [ion] gradients that already exist within the human body,’ according to Anirvan Guha, graduate student at the University of Fribourg’s Adolphe Merkle Institute.

“Then you may be able to create a battery which continuously recharges itself, because these ionic gradients are constantly being re-established within the body.”

Inspired by the electric eel’s ability to generate hundreds of volts, the researchers stacked hundreds of hydrogels containing varying strengths of salt water.

When electrically charged particles—ions—accumulate on either side of a membrane, they form an ion gradient. An unequal concentration of ions across the membrane causes the ion to move across from the area of higher concentration to the area of lower concentration.

This unequal distribution of charge across the membrane creates a difference in electric potential, generating a force that drives ion diffusion until the charges are balanced on both sides of the membrane.

It is the energy from this electric potential—or voltage—that was harvested by the researchers.

By stacking more hydrogel layers on top of each other, they were able to increase the voltage. Generating the 110 volts required thousands of individual hydrogels, which were created using an extremely precise and 3D bioprinter. The result was an array of almost 2,500 gels on a sheet the size of a piece of printer paper.

The team’s next goal is to increase the current running through the hydrogel.

“Right now, we’re in the range of tens to hundreds of microamperes [the basic unit for measuring an electrical current], which is too low to power most electronic devices,” said Guha, who will present the research during the 62nd Biophysical Society Annual Meeting, held 17-21February, in San Francisco, California.

However, the technology is not currently developed enough to be used in medical applications, with Guha cautioning that ‘utilising the body’s ion gradients in this way is an immense challenge which will likely take years of development to overcome’.

Ideally, he hopes it will be ready for testing in human patients in ‘five to ten years’ after ‘further improvements to the power characteristics of the system’.

The results were published in the journal Nature.