Penn State Develops Eel-Inspired Hydrogel Battery

New flexible, high-power design could power medical devices, wearables, and soft robotics.

Jan. 29, 2026 at 5:07pm

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Scientists at Penn State have developed a flexible, high-power hydrogel battery inspired by electric eels. The new design layers multiple types of hydrogels in a precise pattern that mimics the ionic processes electric eels use to produce bursts of electricity, allowing it to achieve power densities higher than previously reported for hydrogel-based batteries. The ultra-thin, water-rich, and conductive hydrogel layers can operate in extreme temperatures without freezing and remain flexible, environmentally stable, and non-toxic.

Why it matters

This eel-inspired hydrogel battery design addresses key limitations of earlier prototypes by increasing power density without requiring external structural support. The flexible, non-toxic, and environmentally stable nature of the battery makes it well-suited for integration into biomedical and near-biological systems like implanted sensors, soft robotics, and wearable electronics.

The details

The researchers used spin coating to deposit four different hydrogel mixtures in ultra-thin, uniform layers just 20 micrometers thick. Optimizing the viscosity and mechanical strength of the hydrogel formulations was crucial to maintaining the layers' integrity during the spin coating process. The resulting power sources reach power densities of around 44 kW/m³, enough to efficiently operate a variety of flexible electronics and medical devices.

  • The research was published in the journal Advanced Science on January 29, 2026.

The players

Penn State

A public research university located in State College, Pennsylvania.

Joseph Najem

Assistant professor of mechanical engineering at Penn State and corresponding author of the study.

Dor Tillinger

Doctoral candidate at Penn State and co-first author of the study.

Wonbae Lee

Co-first author of the study.

Derek Hall

Additional contributor from Penn State.

Haley Tholen

Additional contributor from Penn State.

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What they’re saying

“The electrocytes in electric eels are ultra-thin biological cells, capable of generating over 600 volts of electricity in a brief burst. These cells achieve very high-power densities, meaning they can produce a lot of power from small volumes.”

— Joseph Najem, Assistant professor of mechanical engineering (interestingengineering.com)

“We found that using thin hydrogel naturally reduced the internal resistance of the material, which increased the power densities we could output.”

— Dor Tillinger, Doctoral candidate (interestingengineering.com)

“Conventional formulations would simply fly off the spinning surface during spin coating. Optimizing the viscosity and mechanical strength of our hydrogel was essential to making this approach work.”

— Wonbae Lee, Co-first author (interestingengineering.com)

What’s next

Future work will explore higher power density, improved recharging efficiency, and self-charging capabilities for the eel-inspired hydrogel battery.

The takeaway

This eel-inspired hydrogel battery design represents a significant advancement in flexible, high-power energy storage that could enable a new generation of biomedical and near-biological electronics. By mimicking the ionic processes of electric eels, the researchers have created a safe, non-toxic, and environmentally stable power source that can operate in extreme conditions without rigid supports.