“Next-Gen Energy Innovation: Stretchy, Self-Healing ‘Jelly Batteries’ to Transform Wearables and Brain Implants with Enhanced Flexibility and Longevity”

The soft and sticky substance could power wearable devices or biomedical implants

Researchers at the University of Cambridge have developed soft, stretchable “jelly batteries” that hold potential for powering wearable devices and soft robotics. These innovative materials, inspired by the structure of electric eels, feature a layered design that allows them to deliver electrical current and could be utilized in medical applications such as drug delivery or treating epilepsy. seema

These self-healing jelly batteries exhibit an exceptional ability to stretch more than ten times their original length while retaining conductivity. This marks the first instance of successfully combining stretchability and conductivity in a single material. The findings have been published in the esteemed journal Science Advances.

Made from hydrogels—3D polymer networks consisting of over 60% water—the jelly batteries leverage reversible on/off interactions to control their mechanical properties. Hydrogels, known for their ability to mimic human tissue properties, are promising for use in soft robotics and bioelectronics. However, to be effective in these applications, they must combine both conductivity and stretchability.

“It’s difficult to design a material that is both highly stretchable and highly conductive since those two properties are normally at odds with one another,” said first author Stephen O’Neill from Cambridge’s Yusuf Hamied Department of Chemistry. “Typically, conductivity decreases when a material is stretched.”

“Normally, hydrogels are made of polymers that have a neutral charge, but if we charge them, they can become conductive,” said co-author Dr Jade McCune, also from the Department of Chemistry. “And by changing the salt component of each gel, we can make them sticky and squish them together in multiple layers, so we can build up a larger energy potential.”

Traditional electronics rely on rigid metallic materials with electrons serving as charge carriers. In contrast, jelly batteries use ions as charge carriers, akin to the mechanism in electric eels.

The hydrogels bond firmly to each other through reversible interactions facilitated by barrel-shaped molecules called cucurbiturils, which function like molecular handcuffs. These strong interlayer bonds, created by the molecular handcuffs, allow the jelly batteries to stretch without the layers detaching and without compromising conductivity.

The properties of jelly batteries, being flexible and compatible with human tissue, make them a promising candidate for future use in biomedical implants.

“We can customize the mechanical properties of the hydrogels so they match human tissue,” said Professor Oren Scherman, Director of the Melville Laboratory for Polymer Synthesis, who led the research in collaboration with Professor George Malliaras from the Department of Engineering. “Since they contain no rigid components such as metal, a hydrogel implant would be much less likely to be rejected by the body or cause the build-up of scar tissue.”

The hydrogels are not only soft but also remarkably tough. They can withstand compression without deforming and have the capacity to self-heal when damaged.

The research team plans to conduct experiments with the hydrogels in living organisms to assess their potential for various medical applications.

This research was funded by the European Research Council and the Engineering and Physical Sciences Research Council (EPSRC), under the umbrella of UK Research and Innovation (UKRI). Oren Scherman is a Fellow at Jesus College, Cambridge.

Journal reference:

Stephen J. K. O’Neill, Zehuan Huang, Xiaoyi Chen, Renata L. Sala, Jade A. McCune, George G. Malliaras, Oren A. Scherman. Highly stretchable dynamic hydrogels for soft multilayer electronics. Science Advances, 2024; DOI: 10.1126/sciadv.adn5142