Researchers at the University of Cambridge have developed innovative soft, stretchable “jelly batteries” with potential applications in wearable devices, soft robotics, and even brain implants for drug delivery or treating conditions like epilepsy. Inspired by electric eels, these jelly-like materials feature a layered structure, similar to sticky Lego, enabling them to deliver an electric current.
The jelly batteries, reported in the journal Science Advances, are made from hydrogels: 3D networks of polymers containing over 60% water. These polymers are held together by reversible interactions that control the jelly’s mechanical properties. The ability to precisely control these properties and mimic human tissue characteristics makes hydrogels ideal for soft robotics and bioelectronics. However, achieving both conductivity and stretchability in such materials has been challenging.
“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 Stephen O’Neill from Cambridge’s Yusuf Hamied Department of Chemistry, the first author of the study. “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,” added Dr. Jade McCune, co-author from the Department of Chemistry. “By changing the salt component of each gel, we can make them sticky and squish them together in multiple layers, building up a larger energy potential.”
Unlike conventional electronics, which use rigid metallic materials with electrons as charge carriers, these jelly batteries use ions to carry charge, akin to electric eels. The hydrogels stick strongly to each other due to reversible bonds between different layers, facilitated by barrel-shaped molecules called cucurbiturils, which act like molecular handcuffs. This strong adhesion allows the jelly batteries to stretch without the layers separating or losing conductivity.
The unique properties of these jelly batteries make them promising for 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 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.”
In addition to their softness, these hydrogels are also remarkably tough. They can withstand being squashed without losing their original shape and can self-heal when damaged. The researchers plan to conduct future experiments to test the hydrogels in living organisms, assessing their suitability for a range of medical applications.
By Impact Lab
