From medical implants to soft robots, many emerging technologies need power sources that are flexible, safe, and able to work inside or near living tissue.
Traditional batteries, which are often rigid and contain toxic materials, are poorly suited for these jobs.
Now, researchers at Penn State have turned to an unlikely source of inspiration—the electric eel—to create a new kind of soft, gel-based battery that delivers impressive power while remaining flexible and biocompatible.
Electric eels generate powerful bursts of electricity using specialized cells called electrocytes.
These cells are incredibly thin and stacked in layers, allowing the eel to produce high voltages from a compact, soft structure.
Inspired by this biological design, the Penn State team recreated a similar layered system using hydrogels, which are water-rich materials that can conduct electricity and are generally safe for use around biological tissue.
The researchers designed their power source entirely from hydrogel, avoiding rigid frames or toxic components. This all-gel approach keeps the device soft and flexible, while also allowing it to operate safely in environments where traditional batteries would be unsuitable, such as inside the human body or in wearable electronics.
To build the battery, the team used a technique called spin coating, which spreads materials into extremely thin layers on a rotating surface.
They stacked four different hydrogel layers, each only about 20 micrometers thick—much thinner than a human hair. This thin structure is crucial, because it reduces internal electrical resistance. Lower resistance means electricity can flow more easily, which increases the power output.
Earlier hydrogel-based power sources struggled to deliver high power and often needed external supports to hold them together.
By carefully controlling the thickness and chemistry of the gel layers, the Penn State researchers overcame both problems. Their design produces much higher power than previous hydrogel batteries, while remaining self-supporting and flexible.
Getting the chemistry right was one of the biggest challenges. Standard hydrogels were too runny and would fly off the spinning surface during fabrication. The team adjusted the chemical makeup to balance viscosity, strength, and conductivity, allowing the gels to spread evenly, stay intact, and perform efficiently.
The result is a hydrogel power source with a power density of about 44 kilowatts per cubic meter, which is higher than any previously reported hydrogel-based system. This level of performance is enough to power demanding technologies such as implanted medical sensors, soft robotic components, and advanced wearable devices.
The new material also performs well under harsh conditions. By adding glycerol to the gel, the researchers prevented it from freezing at very low temperatures, allowing it to function down to minus 80 degrees Celsius. The gel also retains moisture far longer than typical hydrogels, staying conductive for days in open air rather than drying out in minutes.
The study, published in the journal Advanced Science, represents a major step toward safe, soft, and powerful energy storage inspired by nature.
The team plans to continue improving the system, with future goals including higher power output, better recharging, and even self-charging capabilities. One day, batteries inspired by electric eels could quietly power the next generation of medical and bio-integrated technologies.
Source: Penn State.
