New research led by the University of Cambridge has resulted in the development of a jelly-like material which, although consists of 80 percent water, can withstand the equivalent of an elephant standing on it, and fully recover to its original shape. The hydrogel looks and feels like a squishy jelly, but behaves like an ultra-hard, shatterproof glass when compressed.
The “super jelly” could be used for a variety of potential applications, including bioelectronics, soft robotics, or even as a cartilage replacement for biomedical use.
How materials behave – whether they are soft or firm – depends upon their molecular structure. Stretchy, rubber-like hydrogels are a popular object of research due to their toughness and self-healing capacities. However, making hydrogels which can withstand being compressed without getting crushed remains a challenge.
“In order to make materials with the mechanical properties we want, we use crosslinkers, where two molecules are joined through a chemical bond,” said study lead author Dr. Zehuan Huang, a postdoctoral fellow in Chemistry at Cambridge. “We use reversible crosslinkers to make soft and stretchy hydrogels, but making a hard and compressible hydrogel is difficult and designing a material with these properties is completely counterintuitive.”
By using barrel-shaped molecules called cucurbiturils – crosslinking molecules, or “molecular handcuffs,” that can hold two guest molecules in their cavities, keeping the polymer networks tightly linked – Dr. Huang and his colleagues managed to design a hydrogel which can withstand a high level of compression.
“The way the hydrogel can withstand compression was surprising, it wasn’t like anything we’ve seen in hydrogels,” said study co-author Dr. Jade McCune, a researcher at University of Cambridge’s Department of Chemistry. “We also found that the compressive strength could be easily controlled through simply changing the chemical structure of the guest molecule inside the handcuff.”
In order to make their glass-like hydrogels, the scientists chose specific guest molecules within the handcuff that allowed the dynamics of the material to “slow down” considerably, and the mechanical performance of the final hydrogel to range from rubber-like to glass-like states.
“To the best of our knowledge, this is the first time that glass-like hydrogels have been made. We’re not just writing something new into the textbooks, which is really exciting, but we’re opening a new chapter in the area of high-performance soft materials,” said Huang.
The scientists are currently working in collaboration with experts from engineering and materials science to further develop these glass-like materials towards biomedical and biolectronic applications.
The study is published in the journal Nature Materials.
Image Credit: Zehuan Huang