Your old jeans could be turned into artificial cartilage

Old denim jeans are set to find new life as artificial cartilage for joint reconstruction, thanks to advanced textile recycling methods being pioneered at Deakin University.

Dr Nolene Byrne and PhD candidate Beini Zeng have discovered how to dissolve denim and manipulate the remains into an aerogel — a low-density material with a range of uses including cartilage bioscaffolding, water filtration and as a separator in advanced battery technology. Dr Byrne said the process worked because denim was made from cotton, a natural polymer comprising cellulose.

“Cellulose is a versatile renewable material, so we can use liquid solvents on waste denim to allow it to be dissolved and regenerated into an aerogel, or a variety of different forms,” she said.

“Aerogels are a class of advanced materials with very low density, sometimes referred to as ‘frozen smoke’ or ‘solid smoke’, and because of this low density they make excellent materials for bioscaffolding, absorption or filtration.

“When we reformed the cellulose, we got something we didn’t expect — an aerogel with a unique porous structure and nanoscopic tunnels running through the sample.”

A sample of the aerogel material. Image credit: Donna Squire.

Dr Byrne said the sticky nature of the denim cellulose solution is likely responsible for the unique aerogel structure that resulted — something ideally suited for use as synthetic cartilage. She said, “That’s exactly what cartilage looks like — you can’t 3D print that material — and now we can shape and tune the aerogel to manipulate the size and distribution of the tunnels to make the ideal shape.”

Dr Wren Greene from Deakin’s Institute for Frontier Materials (IFM), who assisted through testing the suitability of the aerogel materials as cartilage-like bioscaffolds, said the similarities are remarkable.

“The remarkable similarity in the pore network structure of these aerogels and cartilage tissues — even down to the dimensions, orientations and density distribution of pore channels — enables these materials to replicate a special type of ‘weeping’ lubrication mechanism used by cartilage to protect against wear and damage,” Dr Greene said.

Apart from its applications as a cartilage supplement, Dr Byrne said the denim recycling technique will also help contribute to the fight against textile waste — a global challenge her team has been working for more than four years to overcome. And while their previous textile recycling efforts have run into problems with cost-effectiveness, the IFM team’s ‘upcycling’ approach ensured this wasn’t an issue.

“One of the main drawbacks of textile recycling efforts is that any advanced technique requires the use of chemicals, which can then make the procedure less cost-effective,” she said.

“We use environmentally friendly chemicals, and by upcycling our approach to create a more advanced material we can address the limitations affecting other less cost-effective methods.

“We are now entering pilot-scale trials and look to be at commercial scale within 3–5 years with industry support.”

Top image caption: Dr Nolene Byrne and Beini Zeng. Image credit: Donna Squire.