Animal-inspired technology has gone electric. These brightly colored, 3D-printed gels have the potential to create up to 110 volts of electricity in an instant, similar to the electric eel.
Rows of small hydrogel dots are packed with positively and negatively charged ions that combine together to mimic an electric eel’s cellular structure. Printing and stacking these hydrogels produces the highest amount of voltage, while a connection to a larger contact area produces the highest current. Scientists are hoping that this system could potentially lead to a device that generates power from inside of the human body.
“The electric eel is able to create very, very large amounts of power. And we thought that this was remarkable,” said Anirvan Guha, one of the researchers on the project, designed at the University of Fribourg in Switzerland. “So we started to think about whether or not we could create a system that could generate electricity in the same way.”
An eel’s unique ability comes from a specialized organ housing thousands of cells called electrocytes. The chemical make up of these cells allows for a positive or negative charge. The surrounding membranes control the charge by allowing ions to pass through, inciting an electric reaction, or by blocking the ions and returning the organ to a neutral, dormant state.
When an eel is threatened or stalking prey, a neural impulse is sent to the membranes in the electrocytes, and positive ions flood into the cells. In a second, the electric voltage in each cell can go from zero millivolts to 150 millivolts, producing a total of up to 600 volts.
This new power generator works in a similar way.
It uses four different types of hydrogels to mimic the eel’s electrical system. One with a high salt concentration, one with a low salt concentration, and two charged membranes—one negative and one positive.
The first attempt at putting this system together involved using a fluidic autosampler that pushed the gels into sequence in tubes. The more gels in a sequence, the higher the voltage. But the researchers couldn’t build an array long enough to produce the desired voltage.
So the researchers moved on to 3D printing. They printed a sequence of about 2,500 gels on two plastic sheets the size of regular printer paper. When they connected two gel papers, they were able to produce 110 volts of charge within seconds.
This was a huge jump in electricity from the previous method, but the current was still too low for most practical applications.
At the suggestion of a colleague, they tried connecting the gels through a Miura-ori fold, a type of origami fold that allows the gels to stack on a folded sheet. The gels connect simultaneously with a large contact area, more closely resembling the geometry of the eel’s cells. This method increased the current and prevented energy waste by decreasing the time it took for the gels to connect.
Guha says he and his team would love to find a way to make the hydrogels thinner, which would allow for an even higher current. They imagine that one day this system, or one like it, could be used to power internal biological devices such as pacemakers.
“Because the power source is ionic gradients,” Guha says, “our hope is that you could implant one of these devices and the power could be maintained from the ionic gradients within the human body.”
