Cambridge’s self-healing jelly batteries can transform soft robotics

Researchers have created soft, stretchable “jelly batteries” that have potential applications in wearable technology, soft robotics, and even brain implants for drug delivery or treating conditions like epilepsy.

Inspired by electric eels, which use specialized muscle cells known as electrocytes to stun prey, scientists from the University of Cambridge developed these jelly-like materials. These materials possess a layered structure, similar to sticky Legos, enabling them to conduct an electric current.

“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.

Hydrogel breakthrough for stretchable battery

These self-healing jelly batteries can stretch to more than ten times their original length without losing conductivity, marking a significant breakthrough in combining stretchability and conductivity in a single material.

The jelly batteries are composed of hydrogels, which are 3D networks of polymers containing over 60% water. These polymers are held together by reversible on/off interactions that regulate the jelly’s mechanical properties.

“Normally, hydrogels are made of polymers that have a neutral charge, but if we charge them, they can become conductive,” explained co-author Dr. Jade McCune. “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.”

While conventional electronics use rigid metallic materials with electrons as charge carriers, these jelly batteries use ions to carry charge, similar to electric eels.

The hydrogels adhere strongly to each other thanks to reversible bonds formed between different layers, utilizing barrel-shaped molecules called cucurbiturils, which act like molecular handcuffs.

This strong adhesion between layers ensures that the jelly batteries can be stretched without the layers separating and, importantly, without any loss of conductivity.

Transforming biomedical implants

The unique properties of these jelly batteries make them highly promising for biomedical implants , given their softness and ability to conform to human tissue.

“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 alongside 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.”

Besides being soft, these hydrogels are also remarkably tough. They can endure compression without permanently losing shape and possess self-healing capabilities when damaged.

The research team plans to conduct future experiments to test these hydrogels in living organisms, aiming to evaluate their suitability for various medical applications.

The study was published in the journal Science Advances .