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upstart writes in with an IRC submission for RandomFactor:

There's Now an Artificial Cartilage Gel Strong Enough to Work in Knees:

"We set out to make the first hydrogel that has the mechanical properties of cartilage," says chemist Ben Wiley from Duke University.

A significant number of people could benefit from something like this, as more than 790,000 knee replacements happen in the US every year. Currently those replacements - which involve pretty invasive surgery - may only last for a couple of decades before they need to be replaced again.

[...] As with other hydrogels, the main ingredients in this new material are water-absorbing polymers: in this case one polymer made of spaghetti-like strands, intertwined with another polymer that's less flexible and more basket-like. A third polymer, made of cellulose fibres, acts as a mesh holding everything together.

When the material is stretched, it's the third polymer that keeps the gel intact. When it's squeezed, polymers one and two – with negative charges running along their length – repel each other and stick to water, so the original shape can be restored.

The hydrogel passed with top marks in both these crucial categories – stretching and squishing – and showed better performance than other existing hydrogels. In one test of 100,000 repeated pulls, the artificial cartilage held up as well as the porous titanium material used in bone implants.

Journal Reference:
Feichen Yang, Jiacheng Zhao, William J. Koshut, et al. A Synthetic Hydrogel Composite with the Mechanical Behavior and Durability of Cartilage, Advanced Functional Materials (DOI: 10.1002/adfm.202003451)

Original Submission