Power sources for devices used in or around biological tissues must strike a delicate balance: they need to be flexible and non-toxic, yet powerful enough to support cutting-edge technologies such as medical devices and soft robotics. Researchers at Penn State University are turning to an unexpected source for inspiration—the electric eel—to meet these challenging requirements.
By employing a state-of-the-art fabrication method, the team has successfully layered multiple types of hydrogels—a water-rich material known for its ability to conduct electricity—in a pattern that mimics the ionic processes electric eels use to generate electrical bursts. This innovative approach results in power sources with higher power densities than previous hydrogel designs, while maintaining flexibility, environmental stability, and biological compatibility. Their groundbreaking findings were recently published in the journal Advanced Science.
Innovative Approach to Power Density
Joseph Najem, an assistant professor of mechanical engineering and the corresponding author of the paper, explained that while researchers have previously looked to electric fish like eels for inspiration in developing soft power sources, the majority of existing eel-inspired devices have been limited in power output and required mechanical support to function. To overcome these limitations, the Penn State team adjusted the material chemistry to create ultra-thin hydrogels capable of producing more power without mechanical supports.
“The electrocytes in electric eels are ultra-thin biological cells, capable of generating over 600 volts of electricity in a brief burst,” Najem said. “These cells achieve very high-power densities, meaning they can produce a lot of power from small volumes.”
By constructing their power sources solely from hydrogel, the researchers ensured that the batteries remained non-toxic and flexible, even as they increased in power.
Applications in Biomedical Fields
For applications in biomedical and near-biology fields, it is crucial that batteries are compatible with their surroundings, flexible, safe, and ideally able to use available resources for recharging. This necessity motivated the Penn State team to develop their robust power sources within a hydrogel-based system, which operates effectively within biological environments.
The team utilized spin coating, a technique that deposits ultra-thin layers of material on a rotating surface, to layer four different hydrogel mixtures, each just 20 micrometers thick—a fraction of the width of a human hair. This thin geometry reduces internal resistance, which is essential for producing high power, while preserving mechanical strength and flexibility, Najem explained.
Potential Impact and Future Directions
This development could have significant implications for the future of medical devices and soft robotics. By providing a powerful, flexible, and biocompatible energy source, these hydrogel-based batteries could enable the creation of more advanced and integrated medical technologies.
Looking ahead, the team at Penn State is exploring further refinements to their design to enhance power output and efficiency. They are also investigating potential applications in other fields, such as environmental monitoring and wearable technology, where flexible and non-toxic power sources are increasingly in demand.
As the demand for innovative and sustainable power solutions continues to grow, the electric eel-inspired gel battery represents a promising step forward in meeting the needs of modern technology in a biologically compatible manner.
