Soft, stretchy Jelly batteries inspired by electric eel
Researchers at the University of Cambridge have developed innovative, stretchable ‘jelly batteries’ with potential applications in wearable devices, soft robotics and even brain implants for drug delivery and treatment of epilepsy.
Inspired by electric eels, which use modified muscle cells known as electrocytes to generate electric shocks, the Cambridge team created these batteries with a similar layered structure. This design allows them to effectively deliver an electrical current.
The new jelly batteries can stretch more than ten times their original length without loss of conductivity, marking the first successful combination of such high stretchability and conductivity in a single material. The findings have been published in the journal Science Advances.
These batteries are made of hydrogels, which are 3D polymer networks that contain more than 60% water. The polymers are linked together by reversible interactions that control the mechanical properties of the material.
Stephen O’Neill, lead author from the Yusuf Hamied Department of Chemistry in Cambridge, highlighted the challenge in creating a material that is both stretchy and conductive. “It is difficult to design a material that is both highly stretchable and highly conductive because these two properties are normally at odds with each other,” he said. “Normally, when a material is stretched, conductivity decreases.”
Co-author Dr Jade McCune from the Department of Chemistry explains: ‘Normally hydrogels are made of polymers that have a neutral charge, but when we charge them they can become conductive. And by changing the salt component of each gel, we can do that. make them sticky and compress them into multiple layers so we can build greater energy potential.”
Unlike conventional electronics, which rely on rigid materials and electron charge carriers, these jelly batteries use ions to transport the charge, similar to electric eels.
The strong adhesion of the hydrogels is due to reversible bonds formed between the layers using barrel-shaped molecules called cucurbiturils, which act like molecular handcuffs. This strong bond allows the jelly batteries to stretch without the layers breaking apart and without loss of conductivity.
Professor Oren Scherman, director of the Melville Laboratory for Polymer Synthesis, who led the research together with Professor George Malliaras from the Department of Engineering, highlighted the biomedical potential of these hydrogels. “We can tailor the mechanical properties of the hydrogels to match human tissue,” he said. “Because they do not contain rigid components such as metal, a hydrogel implant is much less likely to be rejected by the body or cause scar tissue to build up.”
In addition to their flexibility, the hydrogels are tough and resistant to crushing without permanent deformation. They also possess self-healing properties.
Future research will focus on testing these hydrogels in living organisms to evaluate their medical application potential.
Research report:Highly stretchable dynamic hydrogels for soft multilayer electronics
