'Super jelly' can survive being run over by a car

Credit: Zehuan Huang.

Researchers have developed a material that can hold up to the weight of an elephant, and completely recover to its original shape, even though it's 80% water.

The soft-yet-strong material, developed by a team at the University of Cambridge, looks and feels like a squishy jelly, but acts like an ultra-hard, shatterproof glass when compressed, despite its high water content.

The network of polymers in the non-water portion of the material are held together by on/off interactions. This is the first time that such resistance to compression has been incorporated into a soft material.

The'super jelly' could be used for a wide range of applications, including soft robotics, bioelectronics, or even as a cartilage replacement for biomedical use. The results are reported in a journal.

The way materials behave depends on their structure. It's a challenge to make stretchy, rubber-like hydrogels that can survive being compressed without being crushed.

The University of Cambridge has a credit.

The study's first author said that crosslinkers are used to make materials with mechanical properties. It's difficult to make a hard and compressible hydrogel with the use of crosslinkers, but it's also counterintuitive to design a material with these properties.

The research team used barrel-shaped molecule called Cucurbiturils to make a hydrogel that can tolerate compression. The crosslinking molecule is called the Cucurbituril because it holds two guest molecules in its mouth. The researchers designed guest molecules that prefer to stay inside the cavity for longer than normal, which keeps the network tightly linked, allowing for it to survive compression.

"You would think that at 80% water content, it would burst apart, but it doesn't: it stays intact and is resistant to huge compressive forces," said the Director of the University's Melville Laboratory for Polymer Synthesis. The properties of the hydrogel are not compatible.

The way the hydrogel can resist compression was surprising, said co-author Dr. Jade McCune, also from the Department of Chemistry. The chemical structure of the guest molecule inside the handcuff could be changed to change the strength.

The team made their glass-like hydrogels with guest molecule. The mechanical performance of the final hydrogel ranged from rubber-like to glass-like states, with the mechanical performance of the final handcuff being Altering the molecule structure within the handcuff allowed the dynamics of the material to slow down considerably.

Credit: Zehuan Huang.

"People have spent years making rubber-like hydrogels, but that's just part of the picture," he said. A new class of materials that span the whole range of material properties from rubber-like to glass-like has been created.

The researchers used the material to make a pressure sensor for real-time monitoring of human motions.

This is the first time that glass-like hydrogels have been made. We are opening a new chapter in the area of high- performance soft materials by writing something new into the textbooks.

Researchers from the lab are working with experts from engineering and materials science to develop glass-like materials that can be used in bioelectronics. The research was funded by two organizations.

Nature Materials has more information about Highly compressible glass-like supramolecular polymer networks. There is a DOI: 10.1038/s41563-021-01124-x.

Nature Materials Journal information.

'Super Jelly' can survive being run over by a car.

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